ISSN = 1980-993X (Online) http://www.ambi-agua.net
56th Edition of Revista Ambiente & Água - An Interdisciplinary Journal of Applied Science,
Taubaté, V. 15, N. 2, p. 1-20 Mar/Apr. 2020. (doi:10.4136/ambi-agua.v15.n2) EDITORIAL BOARD Editors Getulio Teixeira Batista (Emeritus Editor) Universidade de Taubaté - UNITAU, BR Nelson Wellausen Dias (Editor-in-Chief), Fundação Instituto Brasileiro de Geografia e Estatística - IBGE, BR
Associate Editors Ana Aparecida da Silva Almeida Universidade de Taubaté (UNITAU), BR Marcelo dos Santos Targa Universidade de Taubaté (UNITAU), BR
Editorial Commission Andrea Giuseppe Capodaglio University of Pavia, ITALY Arianna Callegari Università degli Studi di Pavia, ITALY Antonio Teixeira de Matos Universidade Federal de Minas Gerais (UFMG), BR Apostol Tiberiu University Politechnica of Bucharest, Romênia Claudia M. dos S. Cordovil Centro de estudos de Engenharia Rural (CEER), Lisboa, Portugal Dar Roberts University of California, Santa Barbara, United States Giordano Urbini University of Insubria, Varese, Italy Gustaf Olsson Lund University, Lund, Sweden Hélio Nobile Diniz Inst. Geológico, Sec. do Meio Amb. do Est. de SP (IG/SMA), BR Ignacio Morell Evangelista University Jaume I- Pesticides and Water Research Institute, Spain János Fehér Debrecen University, Hungary Julio Cesar Pascale Palhares Embrapa Pecuária Sudeste, CPPSE, São Carlos, SP, BR Institute of Regional Medicine, National University of the Northeast, Luis Antonio Merino Corrientes, Argentina Maria Cristina Collivignarelli University of Pavia, Depart. of Civil Engineering and Architecture, Italy Massimo Raboni LIUC - University "Cattaneo", School of Industrial Engineering, Italy Petr Hlavínek Brno University of Technology República Tcheca Richarde Marques da Silva Universidade Federal da Paraíba (UFPB), BR Stefan Stanko Slovak Technical University in Bratislava Slovak, Eslováquia Teresa Maria Reyna Universidad Nacional de Córdoba, Argentina Yosio Edemir Shimabukuro Instituto Nacional de Pesquisas Espaciais (INPE), BR Zhongliang Liu Beijing University of Technology, China
Text Editor Theodore D`Alessio, FL, USA, Maria Cristina Bean, FL, USA Reference Editor Liliane Castro, Bibliotecária - CRB/8-6748, Taubaté, BR Peer-Reviewing Process Marcelo Siqueira Targa, UNITAU, BR System Analyst Tiago dos Santos Agostinho, UNITAU, BR Secretary and Communication Luciana Gomes de Oliveira, UNITAU, BR
Library catalog entry by Liliane Castro CRB/8-6748 Revista Ambiente & Água - An Interdisciplinary Journal of Applied Science / Instituto de Pesquisas Ambientais em Bacias Hidrográficas. Taubaté. v. 15, n.2 (2006) - Taubaté: IPABHi, 2020. Quadrimestral (2006 – 2013), Trimestral (2014 – 2016), Bimestral (2017), Publicação Contínua a partir de Janeiro de 2018.
Resumo em português e inglês. ISSN 1980-993X
1. Ciências ambientais. 2. Recursos hídricos. I. Instituto de Pesquisas Ambientais em Bacias Hidrográficas. CDD - 333.705 CDU - (03)556.18 i
TABLE OF CONTENTS COVER: This research intended to discuss methods to simulate characteristic hydraulic times (CHT) in a natural body with focus on Residence Time, Times of Renewal Rates and Water Age. The water body chosen is the Patos Lagoon located in southern Brazil considered the largest choked coastal lagoon in the world with over 300 km in length and an average width of 40 km. The figure shows the results of Water Age simulation for dry and wet seasons. The results show clearly the influence of river inflows in the northern part, and the influence of tides in the southern part. Source: AGUILERA, L. et al. On characteristic hydraulic times through hydrodynamic modelling: discussion and application in Patos Lagoon (RS). Rev. Ambient. Água, Taubaté, vol. 15 n. 2, p. 1-20, 2020. doi:10.4136/ambi-agua.2456
ARTICLES
Land-use change effect on the hydro-dynamic characteristics of soil in the Brazilian semi-arid region 01 1-14 doi:10.4136/ambi-agua.2368 Willames Albuquerque Soares; Simone Rosa da Silva; José Romualdo de Sousa Lima
Sustainable provision of raw water based on the management of ecosystem services in small watersheds 02 1-10 doi:10.4136/ambi-agua.2439 Mateus Marques Bueno; Ricardo Valcarcel; Marcos Gervasio Pereira; Felipe Araújo Mateus
Heavy metals in soils and forage grasses irrigated with Vieira River water, Montes Claros, Brazil, contaminated with sewage wastewater 03 doi:10.4136/ambi-agua.2440 1-11 Matheus Mendes Reis; Leonardo David Tuffi Santos; Ariovaldo José da Silva; Gevany Paulino de Pinho; Leonardo Michel Rocha
Inadequate riparian zone use directly decreases water quality of a low-order urban stream in southern Brazil 04 doi:10.4136/ambi-agua.2451 1-11 Enzo Luigi Crisigiovanni; Elynton Alves do Nascimento; Rodrigo Felipe Bedim Godoy; Paulo Costa de Oliveira-Filho; Carlos Magno de Sousa Vidal; Kelly Geronazzo Martins
Proposal of optimal operation strategy applied to water distribution network with statistical approach 05 doi:10.4136/ambi-agua.2455 1-12 Alex Takeo Yasumura Lima Silva; Fernando das Graças Braga da Silva; André Carlos da Silva; José Antonio Tosta dos Reis; Claudio Lindemberg de Freitas; Victor Eduardo de Mello Valério
Physical and chemical attributes of soil on gully erosion in the Atlantic forest biome doi:10.4136/ambi-agua.2459 06 1-15 João Henrique Gaia Gomes; Marcos Gervasio Pereira; Márcio Rocha Francelino; João Pedro Bessa Larangeira
Removal of solids and chemical oxygen demand in poultry litter anaerobic digestion with different inocula 07 1-15 doi:10.4136/ambi-agua.2469 Joseane Bortolini; Maria Hermínia Ferreira Tavares; Dayane Taine Freitag; Osvaldo Kuczman
Efficiency of horizontal subsurface flow-constructed wetlands considering different support materials and the cultivation positions of plant species 08 1-13 doi:10.4136/ambi-agua.2476 Suymara Toledo Miranda; Antonio Teixeira de Matos; Mateus Pimentel Matos; Claudéty Saraiva
ii
Efficiency of electroflocculation in the treatment of water contaminated by organic waste doi:10.4136/ambi-agua.2484 09 1-10 Aline Nunes Andrade; Rodrigo Vieira Blasques; Paulo Cesar Mendes Villis; Darlan Ferreira Silva; Wolia Costa Gomes
Membrane bioreactor for mall wastewater treatment 10 doi:10.4136/ambi-agua.2489 1-11 Everton Luis Butzen; Gabriel Capellari Santos; Sandrini Slongo Fortuna; Vandré Barbosa Brião
Sorption of Remazol Black B dye in alluvial soils of the Capibaribe River Basin, Pernambuco, Brazil doi:10.4136/ambi-agua.2491 11 1-12 Adriana Thays Araújo Alves; Luisa Thaynara Muricy de Souza Silva; Lucas Ravellys Pyrrho de Alcântara; Vitor Hugo de Oliveira Barros; Severino Martins dos Santos Neto; Valmir Félix de Lima; José Romualdo de Sousa Lima; Artur Paiva Coutinho; Antonio Celso Dantas Antonino
Modeling of the potential distribution of Eichhornia crassipes on a global scale: risks and threats to water ecosystems 12 doi:10.4136/ambi-agua.2421 1-15 Pedro Fialho Cordeiro; Fernando Figueiredo Goulart; Diego Rodrigues Macedo; Mônica de Cássia Souza Campos; Samuel Rodrigues Castro
On characteristic hydraulic times through hydrodynamic modelling: discussion and application in Patos Lagoon (RS) 13 doi:10.4136/ambi-agua.2456 1-20 Laura Aguilera; Ana Lígia Favaro Dos Santos; Paulo Cesar Colonna Rosman
Presence of pesticides, mercury and trihalomethanes in the water supply systems of Ibagué, Colombia: threats to human health 14 doi:10.4136/ambi-agua.2477 1-11 Blanca Lisseth Guzmán Barragán; Manuel Alejandro Gonzalez Rivillas; Manuel Salvador Cuero Villegas; Jose David Olivar Medina
Retrieval and mapping of chlorophyll-a concentration from Sentinel-2 images in an urban river in the semiarid region of Brazil 15 doi:10.4136/ambi-agua.2488 1-13 Alessandro Rhadamek Alves Pereira; João Batista Lopes; Giovana Mira de Espindola; Carlos Ernando da Silva
Variability in phytoplankton community structure and influence on stabilization pond functioning 16 doi:10.4136/ambi-agua.2507 1-13 Emmanuel Bezerra D'Alessandro; Ina de Souza Nogueira; Nora Katia Saavedra del Aguila Hoffmann ·
iii
Ambiente & Água - An Interdisciplinary Journal of Applied Science ISSN 1980-993X – doi:10.4136/1980-993X www.ambi-agua.net E-mail: [email protected]
Land-use change effect on the hydro-dynamic characteristics of soil in the Brazilian semi-arid region
ARTICLES doi:10.4136/ambi-agua.2368
Received: 16 Jan. 2019; Accepted: 06 Feb. 2020
Willames Albuquerque Soares1* ; Simone Rosa da Silva2 ; José Romualdo de Sousa Lima3
1Departamento de Física de Materiais. Escola Politécnica de Pernambuco. Universidade de Pernambuco (UPE), Rua Benfica, n° 455, CEP: 50720-001, Recife, PE, Brazil 2Departamento de Engenharia Civil. Escola Politécnica de Pernambuco. Universidade de Pernambuco (UPE), Rua Benfica, n° 455, CEP: 50720-001, Recife, PE, Brazil. E-mail: [email protected] 3Unidade Acadêmica de Garanhuns. Universidade Federal Rural de Pernambuco (UFRPE), Avenida Bom Pastor, s/n, CEP: 55292-278, Garanhuns, PE, Brazil. E-mail: [email protected] *Corresponding author. E-mail: [email protected]
ABSTRACT The search for better living conditions has led the residents of the Brazilian semi-arid region to plant forage crops, leading to a gradual decrease in the native vegetation (Caatinga) of this region. The effects caused by the replacement of Caatinga with palm, for example, have been little studied, especially with regard to the physical and hydraulic properties of the soil. The objective of this study was to compare the physical-hydraulic characteristics of a litholic neosol in two areas having different vegetation cover: one area cultivated with forage palm (O. ficus-indica) and the other covered by native Caatinga. Differences in soil structure, especially in porosity, between the natural and cultivated soils were observed to control the hydrodynamic processes, resulting in changes in water retention curves and hydraulic conductivity. Natural soil presents low values of hydraulic conductivity when compared to those of cultivated soil. This increase is probably due to soil management required for forage palm cultivation. The natural soil structure, characterized by relatively low saturated hydraulic conductivity values, presents an infiltrability that favors surface runoff. Human activities in the study area have promoted changes in the soil’s physical attributes, decreasing density and increasing porosity. Consequently, there is an increase in water infiltration into the soil and a reduction of runoff in cultivated areas, confirming results obtained in previous studies.
Keywords: forage palm, infiltration, weibull distribution. Efeito da mudança no uso do solo nas características hidrodinâmicas do solo no semiárido Brasileiro
RESUMO A busca por melhores condições de vida tem levado os moradores da região semiárida brasileira a optarem por plantar culturas forrageiras, provocando a diminuição gradativa da vegetação nativa (Caatinga) desta região. A substituição da Caatinga pela palma, por exemplo, tem efeito pouco estudado, sobretudo no tocante as propriedades físico-hídricas do solo. O objetivo deste estudo foi comparar as características físico-hídricas de um Neossolo Litólico This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
2 Willames Albuquerque Soares et al. em duas áreas com diferentes condições de cobertura vegetal: uma cultivada com Palma forrageira (O. ficus-indica) e a outra com Caatinga. Observou-se que as diferenças na estrutura do solo, especialmente na porosidade, entre o solo natural e cultivado, controlam os processos hidrodinâmicos, resultando em alterações nas curvas de retenção de água no solo e de condutividade hidráulica. O solo natural apresentou uma baixa condutividade hidráulica, quando comparada a determinada para o solo cultivado. Esse aumento deve-se provavelmente ao manejo do solo, necessários para o cultivo da palma forrageira. A estrutura do solo natural, caracterizada por valores relativamente baixos de condutividade hidráulica saturada, apresentam uma infiltrabilidade que favorece o escoamento superficial. A antropização do solo na área em estudo promoveu alterações nos atributos físicos dos solos, diminuindo a densidade e aumentando a porosidade. Consequentemente há o aumento da infiltração de água no solo e a redução do escoamento superficial no solo cultivado, corroborando com resultados obtidos em estudos anteriores.
Palavras-chave: infiltração, palma forrageira, semiárido, weibull. 1. INTRODUCTION
Steppe Savanna, or Caatinga, covers about 10% of the total Brazilian territory, an area of 734 thousand km2, and is found mainly in the Northeast Region. It is often marked by two annual dry periods: one long, followed by intermittent rains, and another short, which can become torrentially rainy. The Caatinga has been strongly affected by anthropic action. About 80% of its original ecosystem has already been altered by human processes, mainly through fire and deforestation, practices still common when preparing the soil for agriculture. In addition to destroying vegetation cover, these actions can drastically reduce wildlife populations, affect water quality and disrupt the climate balance and soil balance. Caatinga soils usually have a superficial crust in areas without vegetation which, together with the textural difference between horizons, directly influence the infiltration of water, accentuating the water deficit and causing the few existing plant species in the area to be those that have adapted most fully to this condition (Souza et al., 2016). The root system plays an important role in the infiltration process. Pinheiro et al. (2013) observed that the root system of Caatinga vegetation ranges from 0.60 m to 0.78 m in depth in non-restrictive soils and that the depth of the roots during the dry season is, on average, 10 cm less than during the rainy season. This fact indicates an adaptation strategy and generates secondary porosity of the soil in order to increase the infiltration of water into the root zone. However, crops lead to modifications to the soil attributes depending on the intensity of soil preparation and the type of management used. Well-adapted to the conditions in the semi-arid region of Pernambuco, forage palm (Opuntia ficus-indica) was introduced into Brazil at the end of the 19th century and is the xerophytic agricultural option with the greatest potential in the Northeast, surpassing 400,000 hectares. It has been used for years as feed for cattle herds during the dry season, mainly due to its high potential for phytomass production. The requirements for forage palm cultivation, such as climatic conditions, soil texture varying from sandy to clayey, and the variation between nocturnal and diurnal temperatures are all found in Northeast Brazil (Edivani et al., 2013). Genin et al. (2017) evaluated the natural regeneration of argania (Argania spinosa) and palm fruit production (Opuntia fícus-indica) in the arid pre-Saharan zone of south-west Morocco. They observed that the perennial planting of palm allied with the exclusion of pasture for cattle, creates conditions favorable for forest recovery. They also point out that these synergies could be a basis for promoting sustainable development and ecological restoration,
Rev. Ambient. Água vol. 15 n. 2, e2368 - Taubaté 2020
Land-use change effect on the … 3 as well as inspiring alternative guidelines for more integrated plans that combat desertification. Oliveira Junior et al. (2014) evaluated the impact of pasture on the hydrodynamic properties of a regolithic neo-soil in the Agreste Region of Pernambuco, and observed that the use of the soil for pastureland significantly altered its properties when compared with those of the natural Caatinga soil, mainly with regard to soil density and hydraulic conductivity. Infiltration in semi-arid areas is often limited by low hydraulic conductivity and extreme levels of water repellency which, when combined with a high intensity of precipitation, results in excess infiltration as a dominant surface runoff mechanism. Farrick and Branfireun (2014), when studying dry tropical forests, found hydraulic conductivity values between 9 and 164 mm h-1, greater than rainfall intensity for more than 75% of rain events. They also observed that 70% of the infiltrated water is contained in the upper 30 cm of soil. Kargas et al. (2012) assessed the effects of surface conditions on water infiltration into the soil in semi-arid climates in Greece and concluded that cultivation reduces bulk soil density, resulting in changes to the water retention curve in soil and in saturated hydraulic conductivity. Leite et al. (2018) studied the hydrodynamic behavior of the Brazilian Caatinga in four stages of degradation. They noticed that the infiltration of water into the soil was lower than the saturated hydraulic conductivity and associate this fact to the soil slope generated by the impact of the rain. They also observed that the growth of the Caatinga promotes the recovery of the hydraulic properties of the soil, increasing saturated hydraulic conductivity and infiltration. Mendonça et al. (2009), studying the infiltration of water in a clayey yellow red latosol located in the Araripe Plateau in Ceará, observed that the litter and organic matter produced by the native forest protect the soil from rainfall impact and help maintain a high infiltration capacity when compared to deforested areas. Soares (2018a) estimated different rainfall events in order to analyze the effect of precipitation intensity on soil/water dynamics in the semi-arid region of Brazil. He noted that the hydrodynamic characteristics of the natural soil where Caatinga is found cause the upper 40 centimeters to retain most of the precipitated water. By altering the physical characteristics of the soil of the region, infiltration increases and water is retained at a greater depth, so that the native vegetation cannot absorb the stored water. Soil use and management impact its physical quality, mainly soil aeration. However, it also makes the soil susceptible to erosion above all for monocultures (Lima et al., 2018). Replacing native vegetation by forage palm crop, due to soil management necessary for cultivation, modifies the physical properties of the soil in ways that can make restoration of native forest impossible (Soares, 2018b). Due to the variability in the magnitude of responses to changes in soil use and soil cover, site-specific studies are needed in order to understand the influences caused by soil cover changes in semi-arid environments (Owuor et al., 2016). However, few studies have evaluated the hydrodynamic behavior of the Caatinga vegetation compared to other crops. This study therefore sought to compare the hydraulic characteristics of a litholic neosol in two areas having different vegetative cover: one cultivated with forage palm (O. ficus-indica) and the other with native Caatinga. The hydrodynamic characteristics of the soil were determined using three- dimensional infiltration tests and by analyzing the soil granulometry.
2. MATERIALS AND METHODS
2.1. Study location The study was conducted in the municipality of São Bento do Una, Pernambuco, in the southern Agreste mesoregion (geographical coordinates: 8°36'37'' S by 36°21'45'' W at approximately 621 m altitude, Figure 1) from April to June 2017. The plots consisted of 2.0 ha of natural soil, where the Caatinga vegetation is preexistent, and 4.5 ha of soil cultivated with
Rev. Ambient. Água vol. 15 n. 2, e2368 - Taubaté 2020
4 Willames Albuquerque Soares et al. forage palm (O. ficus-indica). The soil of the study area is classified as a litholic neosol with local relief characterized as gently undulated with an average slope of 1.6%. The predominant climate is semi-arid with a hot and dry summer and a rainy season between the months of April and June. The climate is classified as BSh according to the Köppen-Geiger classification scheme. The mean annual precipitation does not exceed 300 mm and the natural vegetation is composed of hyper xerophilic Caatinga. According to local residents, some more than 90 years old, the Caatinga vegetation of this plot has never been deforested. The most common shrubs are Black Jurema (Mimosa hostilis Benth.), White Jurema (Mimosa hostilis) and the more rare Umbuzeiro (Spondias tuberosa). Among the cacti found, the most notable are the Foxtail (Harrisia adscendens), Facheiro (Pilosocereus catingicola), Mandacaru (Cereus jamacaru), and Xique-xique (Pilosocereus gounellei). Due to a severe dry period, the caatinga was found to be noticeably degraded, resembling an area studied by Leite et al. (2018) that had been deforested and recovered 35 years ago. In the plot where the native vegetation has been replaced by forage palm (O. ficus-indica) for at least 30 years, the soil is turned by machinery, while planting and organic fertilization are performed manually, the latter occurring twice during each crop cycle, once during planting and once at one year. In both cases, approximately 3 t ha-1 is used. Non-deformed soil samples were collected from the 0-20 cm depth layer in two distinct areas: under Caatinga and under forage palm (O. ficus-indica). In order to determine the hydrodynamic properties of the soil, granulometry and infiltration tests were carried out at both sites. In Figure 1b, we can see a stretch of the 2 ha of Caatinga. Although the plants are xerophiles, the scarcity of rainfall over the last five years has drastically reduced their vegetative density.In this area, the predominant arboreal vegetation is composed mainly of black jurema (Mimosa hostilis Benth.), white jurema (Mimosa hostilis) and more rarely umbuzeiro (Spondias tuberosa). Among the cacti found were the foxtail (Harrisia adscendens), the woodpecker (Pilosocereus catingicola), the mandacaru (Cereus jamacaru) and the xique-xique (Pilosocereus gounellei). The soil is compacted, shallow, and stony, with fragments of rock on the surface. At a depth of 0.4 m, it becomes impossible to excavate without the use of machinery, due to the large quantity of rocks. In Figure 1c, the 4.5 ha of soil cultivated with spineless cactus (O. ficus-indica) is shown. Along with the cultivation, a large and diverse amount of weeds can be seen, which are periodically removed. Due to the scarcity of water, the crop does not grow satisfactorily. The leaves are small, twisted, and largely a non-characteristic color with a yellowish tint. Fertilization is carried out at the beginning of planting and is not repeated until the time of harvest. Initially, the distance between plants is approximately 0.5 m. Between lines, the distance is about 1.0 m. Both distances decrease as the crop grows. Due to the treatment necessary for cultivation, the soil is not compacted nor does it contain rocky fragments within the upper 0.4 m of its depth. From April 1st to June 30th, 2017, a total of rainfall of 543.6 mm, and its distribution is irregular throughout the period. Of the 91 days of study, 30 had no rainfall. In 44 days, precipitation occurred up to 10 mm and only in 17 days had precipitation greater than 10 mm. The biggest rain event (74.6 mm) occurred on 05/28/2017 (Figure 2). That is, the rains were of low intensity but with high frequency.
Rev. Ambient. Água vol. 15 n. 2, e2368 - Taubaté 2020
Land-use change effect on the … 5
a)
b) c)
Figure 1. a) Localization map of the study region. b) Caatinga found in the study area. c) Spineless cactus (O. Ficus-Indica) cultivation in the study area.
Rev. Ambient. Água vol. 15 n. 2, e2368 - Taubaté 2020
6 Willames Albuquerque Soares et al.
Figure 2. Rainfall from April 1st to June 30th, 2017.
2.2. Granulometric tests The granulometric analysis was performed using the ABNT (2016) method, which makes it possible to determine the diameters of the finer particles (clay and silt) through sedimentation and the coarser ones (sand) through sieving. A sigmoid curve with asymptotic limits and an exponential growth rate, proposed by Weibull, with three adjustment parameters (dm, β and δ), was fitted to the points obtained from the particle size test Equation 1:
−훽푑훿 퐹푑 = 100 − (100 − 푑푚)푒 (1)
Where d is the particle diameter (mm), and Fd is the percentage of particles smaller or equal to d. The adjustment parameters to fit the model to the known points of the particle size distribution curve were determined optimally, considering as a criterion the minimization of an object function Equation 2:
푁 2 퐹푂 = ∑푖=1[푥(𝑖) − 푥̂(𝑖)] (2)
Where 푥(𝑖), 푥̂(𝑖) are the measured and calculated values of the accumulated fractions, for the respective fraction i. From the fitted grain-size curves, the water retention curve was estimated using the model proposed by Arya and Heitman (2015), which calculates the values of moisture and matric potential from the values for particle diameter and concentration obtained through the granulometric analysis. The water content in the soil was estimated from the particle size distribution, as a contribution of each fraction to the wetting of the soil, using the Equation 3:
푖 휃푖 = 휙 ∑푖=0 푤푖 (3)
3 -3 -1 Where φ represents the porosity (m .m ), wi is the mass fraction of i (kg kg ), calculated by means of a sigmoidal function fitted to the soil particle size distribution data. The soil matric potential (hi)was calculated from the capillarity and from the pore radius (Equation 4):
Rev. Ambient. Água vol. 15 n. 2, e2368 - Taubaté 2020
Land-use change effect on the … 7
2𝜎 ℎ푖 = (4) 0.717훷(푤𝑖/푝푏) 𝜌푤푔 4/3 √ 3푤𝑖 ( 3 ) 푅𝑖 4휋푅𝑖 푝푝
Where σ is the surface tension at the air-water interface (0.0728 N m-1), g is the acceleration -2 of gravity (9.81 m s ), Ri is the radius of the particles, and ρw, pp, and pb are the densities of water, apparent soil, and particles (kg m-3). This methodology has been well evaluated for Brazilian soils (Soares and Hammecker, 2017).
2.3. Infiltration tests Simple-ring infiltrators with a diameter of 150 mm and height of approximately eight centimeters were used in the infiltration tests. In order to minimize the structural disturbance and ensure a vertical flow on the soil surface, they were embedded about one centimeter into the soil. According to the applied methodology, undeformed samples were collected to determine the soil density (using an Uhland auger) and deformed samples to determine the initial and final volumetric contents of water and to obtain the granulometric curve. A fixed volume of water was then poured into the cylinder at time zero: the elapsed time during infiltration of the known water volume could thus be measured. Once the initial volume had been completely infiltrated, a second known volume of water was added to the cylinder, and the time required to infiltrate was measured. This procedure was repeated for a series of volumes to reach steady state. The three-dimensional infiltration of water into the soil was modeled using the analytical equation for long times proposed by Haverkamp et al. (1994) in order to obtain the saturated hydraulic conductivity (Ks) and the sorptivity (S). The simplified form of this Equation 5 is defined by:
훾푆2 푆2 1 퐼3퐷 = [퐾푠 + ] 푡 + 푙푛 ( ) (5) 푟푑(휃0−휃푛) 2(퐾푠−퐾푛)(1−훽) 훽
Where I3D is the three-dimensional infiltration, θn and θ0 are the initial and final humidities 3 -3 (mm .mm ), rd is the infiltrator radius (mm), t is the time (s), Kn is the hydraulic conductivity at the start of the test (mm s-1), and γ and β are dimensionless parameters. Capillarity and gravity affect three-dimensional infiltration. This influence can be estimated through the capillary length scale, λC (White and Sully, 1987) and the characteristic radius of hydraulically active pores, λm (Philip, 1987), determined by Equations 6 and 7:
훿푆2 휆푐 = (6) (휃푓−휃𝑖)퐾푠
𝜎 휆푚 = (7) 𝜌푤푔휆푐
-1 Where σ is surface tension of water (0.0728 N m ), ρw is the specific mass of water (103 kg m-3), g is the acceleration of gravity (9.81 m s-2), and δ is the diffusivity shape parameter (0.55). λC represents the relative importance of capillary forces compared to gravity, when water is transmitted through the soil with initial moisture (θi), and λm defines the average size of the pores that participate in the infiltration process. The higher the λm, the greater the effect of gravity compared to capillarity.
Rev. Ambient. Água vol. 15 n. 2, e2368 - Taubaté 2020
8 Willames Albuquerque Soares et al.
Six point tests were performed in each of the plots, with three repetitions, totaling 36 samples. The simple-ring infiltrometer test is an excellent alternative considering attributes such as preparation and test execution costs, time required for its execution, and the fact that it has been used by various authors (Souza et al., 2016; Oliveira and Soares, 2017). A disadvantage of this infiltrator is that it does not characterize the surface sealing generated by the impact of rain drops. 2.4. Hydrodynamic Characterization The results obtained for volumetric moisture (θ) and matric potential (h) were fitted to the Equations 8 and 9 proposed by Van Genuchten (1980):
휃푠−휃푟 휃(ℎ) = 휃푟 + 푛 1−2/푛 (8) ℎ [1+| | ] ℎ푔 2 1 1−2/푛 0.5 휃−휃푟 휃−휃푟 1−2/푛 퐾(휃) = 퐾푠 ( ) [1 − (1 − ( ) ) ] (9) 휃푠−휃푟 휃푠−휃푟
In this way, the values for residual (θr) and saturated (θs) volumetric humidity, the pore size distribution index (n), and the bubbling pressure (hg) were determined. 2.5. Soil repellency to water In order to estimate the degree of soil repellency to water, the water droplet penetration time (WDPT) method was used, which consists of applying two drops of water (around 40 μl) with a Pasteur pipette, and then measuring the time taken for these drops to penetrate the sample. Ten point tests were performed in each of the plots, with three repetitions, totaling 60 samples. 3. RESULTS AND DISCUSSION 3.1. Granulometry and infiltration tests From the sieving and sedimentation tests, it was possible to determine the granulometric fractions of the studied soils. For the natural soil, the average fractions of sand, silt, and clay were 72.13%, 17.24%, and 10.63%, respectively. For the cultivated soil, the average fractions of sand, silt, and clay were 68.19%, 16.71%, and 15.10%, respectively. The differences between these soils were not considered to be significant (t-test), and these soils were classified texturally as sandy loam (Table 1). These results were expected, as the original material was identical for the two classes of land use. In both cases, the amount of sand present is considerably higher than the clay and silt fractions.
Table 1. Granulometric fractions, density (ρ), porosity (φ), and water droplet penetration time (WDPT) of natural and cultivated soils. Soil Clay (%) Silt (%) Sand (%) ρ (g cm-3) φ (%) WDPT(s) Natural 10.63±3.2 17.24±1.5 72.13±2.6 1.69±0.04 36.23±3.7 3.84±0.61 Cultivated 15.10±2.7 16.71±1.2 68.19±3.1 1.43±0.05 46.04±3.2 0.82±0.37
The similarity in soil textures is important because it suggests that possible differences in other physical and hydraulic properties (between natural and cultivated areas) can be attributed with some degree of confidence to the effects caused by use of the soil. The densities of the natural and cultivated soils were 1.69 g cm-3 and 1.43 g cm-3, respectively. Natural soil was expected to have a higher density, since the soil is plowed in preparation for planting the palms.
Rev. Ambient. Água vol. 15 n. 2, e2368 - Taubaté 2020
Land-use change effect on the … 9
Another fact that might contribute to higher compaction for the natural soil is its slope, which causes an increase in surface runoff. The slope of the natural soil was 1.6% while the portion of cultivated soil had a slope of only 1%. The values determined for the density are close to those found in other studies carried out in regions having the same characteristics. Rodrigues et al. (2016), found values between 1.46 g cm-3 and 1.61 g cm-3 for yellow argisol in a region of the Caatinga, in Juazeiro, BA. Oliveira Junior et al. (2014) observed values of 1.67 g cm-3 and 1.14 g cm-3 for natural regolithic neosol in the municipality of São João, PE, and 1.56 g cm-3 and 1.28 g cm-3 for soil planted with grass (Brachiaria decumbens Stapf). Density directly affects soil porosity, retention, and conductivity (Kargas et al., 2012). There was an increase of approximately 27% in the porosity of the cultivated soil (46.04%) compared to the natural soil (36.23%). The same behavior was observed by Rodrigues et al. (2016), who found an increase of about 26% in yellow argisol in the municipality of Juazeiro, BA. According to the classification by Bisdom, both soils present values that classify them as hydrophilic. However, it is worth mentioning that the values obtained for the natural soil were much higher than the values obtained for the cultivated soil. The highest WDPT values for the natural soil result from the higher concentration of fresh and/or partially decomposed matter, different from the organic matter found in the cultivated soil, which is already in an advanced state of decomposition. The parameters for the grain-size curve proposed by Weibull (Equation 1) for natural and cultivated soils were adjusted appropriately, with an r2 greater than 0.99. For the natural soil, the values of the parameters dm, β and δ were 10.62, 2.53, and 1.18, respectively. For the cultivated soil, the values were 15.24, 1.84, and 1.52. Although different, they are within the same order of magnitude and were able to efficiently fit to the measured data, with errors of less than 5%. From the field study, mean values were found for accumulated infiltration and the infiltration rate. In the natural soil, infiltration of 37.35 mm of water occurred after a time of 4489 s. Initially, the infiltration rate was 0.027 mm s-1 and by the end of the test, the rate had fallen to 0.005 mm s-1. These values are different from those obtained for cultivated soil, which had a total infiltration of 87.15 mm in a time 1046 s. At the start of the test, the infiltration rate was 0.231 mm s-1 and by the end of the test, it was 0.072 mm s-1. The water infiltration into the soil depends on porosity and on other factors that can interfere with soil pores, such as clay content, root systems, and initial moisture, among others (Pinheiro et al., 2013). As the initial moisture of both soils was practically the same (0.04 cm3.cm-3) and the amount of clay in the samples was not significantly different, the alterations in the infiltrated volumes result from the difference in porosity and in the repellency of water by the soil, which is higher for the Caatinga (Table 2).
Table 2. Adjustment parameters (dm, β, δ), for the granulometric curves of natural and cultivated soils.
Soil dm β δ Error (%) Natural 10.62 2.53 1.18 1.23 Cultivated 15.24 1.84 1.52 3.03
3.2. Hydrodynamic characterization of the soil By fitting the van Genuchten equation (Equation 8) to the measured retention data, it was possible to estimate the values for bubbling pressure, the hydrodynamic parameters, and the residual and saturated volumetric moisture for both natural soil and cultivated soil (Table 3). The values found for all the parameters related to the natural soil were within the ranges Rev. Ambient. Água vol. 15 n. 2, e2368 - Taubaté 2020
10 Willames Albuquerque Soares et al. determined by Oliveira Júnior et al. (2014), when comparing the hydrodynamic variability of soils with vegetation cover and with grass, in the semiarid region of Pernambuco.
Table 3. Bubble pressure (hg), hydrodynamic parameters (n and m), residual and saturated volumetric moisture (θr and θs), saturated hydraulic conductivity (Ks), sorptivity (S), capillary length scale (λC), and characteristic pore radius (λm) for natural and cultivated soils.
│hg│ n m θr θs KS S λC λm Soil (cm) (cm3 cm-3) (cm3 cm-3) (mm s-1) (mm s-0.5) (mm) (mm) Natural 12.64 2.64 0.24 0.033 0.344 5.38x10-3 0.190 300.40 0.02 Cultivated 7.62 2.95 0.32 0.065 0.437 7.78x10-2 0.349 4.07 1.80
The bubbling pressure values obtained were 12.64 cm and 7.62 cm for natural soil and cultivated soil, respectively. The higher value indicates that greater pressure is needed to unsaturate the moisture and begin withdrawing water into the soil. In other words, the crop management techniques have modified the hydrodynamic characteristics of the soil, making the soil lose water more easily. The natural soil presented a distribution index (n) of 2.64 and the cultivated soil had an n of 2.95. The higher the value, the lower the retention of water in the soil. As an example, for a matric potential of 0.42 m, natural and cultured soils have a θ of 0.18 cm³ cm-3 and 0.12 cm³ cm-3, respectively. This parameter influences the hydraulic conductivity curve of the soil. For example, for θ = 0.26 cm³ cm-3, the natural and cultivated soils had a K(θ) of 0.0002 mm s-1 and 0.0094 mm s-1, respectively. 3 -3 The natural soil had a θr of 0.033 cm cm , about 50% of the value obtained for the cultivated soil, which was 0.065 cm3 cm-3. These values indicate that the natural soil allows water to be withdrawn from the soil by vegetation even when less water is available than in the cultivated soil. 3 -3 The natural soil had a θS of 0.344 cm cm , about 80% of the value obtained for the cultivated soil, which was 0.437 cm3 cm-3. These values show that, for the same matric potential, the cultivated soil contains more water available to plants, a direct consequence of the management necessary for the crop that alters the soil porosity. By fitting the equation proposed by Haverkamp (Equation 5) to the data obtained from the infiltration tests, it was possible to estimate the values for saturated hydraulic conductivity, sorptivity, capillary length scale, and the characteristic pore radius for both natural and cultivated soil. The values found for all parameters related to the natural soil were within the ranges determined by Oliveira Júnior et al. (2014), when comparing the hydrodynamic variability of soils with vegetation cover and with grass, in the semiarid region of Pernambuco. The upper limit of the hydraulic conductivity curve is determined by KS. This parameter was found to be different in the two soils studied. The natural soil had a KS of 5.38 x 10-3 mm s-1, which was only about 7.5% of that obtained for cultivated soil, 7.78 x 10-2 mm s-1. This provides evidence that the conduction of water in the natural soil is much less than in the anthropogenic soil. The values found are within the range determined by Leite et al. (2018), when studying the hydrodynamic behavior of the Caatinga in four different stages of degradation. The capacity to absorb water as soon as it reaches the ground is represented by S. The natural soil presented an S value of 0.190 mm s-0.5, about 54% of that obtained for cultivated soil, which was 0.349 mm s-0.5. That is, this property of the soil has been altered due to human action, which can change the ability of the natural soil to be reconstituted with the same original characteristics. For natural soil, the values of λm and λC were 0.02 mm and 300 mm, respectively. These
Rev. Ambient. Água vol. 15 n. 2, e2368 - Taubaté 2020
Land-use change effect on the … 11 values indicate that, for natural soil, infiltration is governed by capillary forces with gravity having little effect. For cultivated soil, the behavior is the reverse. Infiltration is predominantly governed by gravity, while capillary action has little influence. The values found for λm and λC were 1.80 mm and 4.07 mm. This demonstrates the importance of soil structure, as soils with the same texture can have very different hydraulic behaviors. As expected, the increase in the characteristic radius of the pores that effectively carry water implied an increase in S and KS. Figure 3a shows the water retention curves of the natural and cultivated soils. It can be observed that, despite their similarities, the representative curve for natural soil presents extreme values different from those found for the cultivated soil. Probably due to soil management, which increased soil aeration. The inflection points are close, as evidenced by the values of│hg│. As shown in the water retention curves for the soils, the hydraulic conductivity curves of natural and cultivated soils present similarities with greater differences at the extremes (Figure 3b). However, the maximum water conduction value for soil cultivated with forage palm is an order of magnitude greater than that determined for soil cultivated with natural vegetation. This causes rainwater to seep into the soil faster, increasing the possibility of soil erosion.
Figure 3. a) Water retention curves in natural and cultivated soils; b) Hydraulic conductivity curves for natural and cultivated soils.
Although the differences in hydrodynamic characteristics appear to be small, they suggest an influence over the entire hydrological cycle at the locality. The natural soil presents characteristics that attenuate the infiltration and conduction of water into its interior, causing a greater surface runoff, characteristic of the region. With the replacement of the natural vegetation by the forage palm crop, a decrease in this flow occurs. These results agree with those found by Alaoui et al. (2011), who observed that surface runoff is controlled by saturated hydraulic conductivity and soil bulk density.
4. CONCLUSIONS
The adjustment of the Weibull equation proved to be appropriate, robust, and fully adapted to modeling the granulometric curves for the studied soils, allowing the methodology proposed by Arya and Heitman to be used to estimate the water retention curve for the soil. The methodology proposed by Haverkamp provided acceptable values for the sorptivity and saturated hydraulic conductivity of the natural and cultivated soils, giving precise adjustments of accumulated infiltrations. The differences in structure, especially in porosity, between the natural and cultivated soils control the hydrodynamic processes, resulting in alterations in the water retention curves and in hydraulic conductivity.
Rev. Ambient. Água vol. 15 n. 2, e2368 - Taubaté 2020
12 Willames Albuquerque Soares et al.
The natural soil structure, characterized by relatively low values of KS, presents an infiltrability that favors surface runoff. Soil anthropization in the study area has promoted changes in the soil’s physical attributes, decreasing its density and increasing porosity. Consequently, there is an increase in water infiltration into the soil and a reduction of runoff, corroborating results obtained in previous studies. Conversion of forests to cropland is the main land-cover change in the Caatinga, and it has a major effect on soil hydraulic properties. Our study shows that a difference in infiltrability across the two sites is explained by a change in soil structure, arising from soil management.
5. ACKNOWLEDGEMENTS
The author would like to thank the Pernambuco State Foundation for Support of Science and Technology (FACEPE) for their financial support through research assistance (APQ 0582- 01/15).
6. REFERENCES
ABNT. NBR 7181 - Solo: análise granulométrica. Método de ensaio. Rio de Janeiro, 2016. 12 p. ALAOUI, A.; CADUFF, U.; GERKE, H. H.; WEINGARTNER, R. Preferential flow effects on infiltration and runoff in grassland and forest soils. Vadoze Zone Journal, n.10, p.367-377, 2011. http://dx.doi.org/10.2136/vzj2010.0076 ARYA, L. M.; HEITMAN, J. L. A non-empirical method for computing pore radii and soil water characteristics from particle-size distribution. Soil Science Society of American Journal, n. 6, p. 1537-1544, 2015. https://dx.doi.org/10.2136/sssaj2015.04.0145 EDIVANI, R. L.; FERNANDES, P. D.; CARNEIRO, M. S. S.; NEDER, D. G.; ARAUJO, J. S.; ANDRADE, A. P.; SOUTO FILHO, L. T. Acúmulo de biomassa e crescimento radicular da palma forrageira em diferentes épocas de colheita. Revista Acadêmica Ciência Animal, n. 4, p. 373-381, 2013. https://dx.doi.org/10.7213/academico.011.004.AO04 FARRICK, K. K.; BRANFIREUN, B. A. Infiltration and soil water dynamics in a tropical dry forest: it may be dry but definitely not arid. Hydrological processes, n. 8, p. 4377–4387, 2014. http://dx.doi.org/10.1002/hyp.10177 GENIN, M.; ALIFRIQUI, M.; FAKHECH, A.; HAFDI, M.; OUAHMANE, L.; GENIN, D. Back to forests in pre-Saharan Morocco? When prickly pear cultivation and traditional agropastoralism reduction promote argan tree regeneration. Silva Fennica, n. 51, p. 1- 22, 2017. https://dx.doi.org/10.14214/sf.1618 HAVERKAMP, R.; ROSS, P. J.; SMETTEM, K. R. J.; PARLANGE, J. Y. Three dimensional analysis of infiltration from the disc infiltrometer 2. Physically based infiltration equation. Water Resources Research, n.30, p. 2931-2935, 1994. http://doi.org/10.1029/94WR01788 KARGAS, G.; KERKIDES, P.; POULOVASSILIS, A. Infiltration of rainwater in semi-arid areas under three land surface treatments. Soil & Tillage Research, n. 120, p. 15–24, 2012. https://dx.doi.org/10.1016/j.still.2012.01.004
Rev. Ambient. Água vol. 15 n. 2, e2368 - Taubaté 2020
Land-use change effect on the … 13
LEITE, A. M. P.; SOUZA, E. S.; SANTOS, E. S.; GOME, J. R.; CANTALICE, J. R.; WILCOX, B. P. The influence of forest regrowth on soil hydraulic properties and erosion in a semiarid region of Brazil. Ecohydrology, n. 11, p. 31-33, 2018. https://dx.doi.org/10.1002/eco.1910 LIMA, P. L. T.; SILVA, M. L. N.; QUINTON, J. N.; BATISTA, P. V. G.; CÂNDIDO, B. M.; CURI, N. Relationship among crop systems, soil cover, and water erosion on a Typic Hapludox. Revista Brasileira de Ciências do Solo, v. 42, p. 1–16, 2018. https://dx.doi.org/10.1590/18069657rbcs20170081 MENDONÇA, L. A. R.; VÁSQUEZ, M. A. N.; FEITOSA, J. V.; OLIVEIRA, J. F.; FRANCA, R. M.; VÁSQUEZ, E. M. F.; FRISCHKORN, H. Avaliação da capacidade de infiltração de solos submetidos a diferentes tipos de manejo. Engenharia Sanitária e Ambiental, n. 1, p. 89-98, 2009. https://dx.doi.org/10.1590/S1413-41522009000100010 OLIVEIRA JUNIOR, J. A. S.; SOUZA, E. S.; CORREA, M. M.; LIMA, J. R. S.; SOUZA, R. M. S.; SILVA FILHO, L. A. S. Variabilidade espacial de propriedades hidrodinâmicas de um Neossolo Regolítico sob pastagem e Caatinga. Revista Brasileira de Engenharia Agrícola e Ambiental, n. 6, p. 631-639, 2014. https://dx.doi.org/10.1590/S1415- 43662014000600010 OLIVEIRA, D. B. C.; SOARES, W. A. Desempenho de modelos de infiltração tridimensional de água no solo. Revista Diálogos, n. 18, p. 519-544, 2017. http://dx.doi.org/10.13115/2236-1499v2n18p519 OWUOR, S. O.; BUTTERBACH-BAHL, K.; GUZHA, A. C.; RUFINO, M. C.; PELSTER, D. E.; DÍAZ-PINÉS, E.; BREUER, L. Groundwater recharge rates and surface runoff response to land use and land cover changes in semi-arid environments. Ecological Processes, n.16, p. 1-21, 2016. https://dx.doi.org/10.1186/s13717-016-0060-6 PHILIP, J. R. The quasi-linear analysis, the scattering analog, and other aspects of infiltration and seepage. In: FOK, Y.S. (Ed.). Infiltration development and application. Honolulu: Water Resources Research Center, 1987. p.1-27. PINHEIRO, E. A. R.; COSTA, C. A. G.; ARAÚJO, J. C. Effective root depth of the Caatinga biome. Journal of Arid Environments, n. 89, p. 1-4, 2013. https://dx.doi.org/10.1016/j.jaridenv.2012.10.003 RODRIGUES, M. A.; SOUZA, C.; LIMA, D. D.; SILVA, S. D. P.; ALVES, D. C.; MACHADO, N. S. Impacto do cultivo do coqueiro irrigado na qualidade física do solo na região semiárida brasileira. Ciencia del suelo, n. 1, p. 139-144, 2016. SOARES, W. A.; HAMMECKER, C. Comparison of Mathematical Models for the layout of Granulometric Curves of Brazilian Soils. Revista de Geografia, n. 1, p. 251-267, 2017. SOARES, W. A. Análise da dinâmica da água em um solo não saturado sob condições de chuvas simuladas. Revista águas subterrâneas, n. 2, p. 200-209, 2018a. https://dx.doi.org/10.14295/ras.v32i2.29109 SOARES, W. A. Impact of spineless cactus cultivation (O. Ficus-indica) on the thermal characteristics of soil. Revista Ambiente & Água, v. 13, n. 1, p. 1-12, 2018b. https://dx.doi.org/10.4136/ambi-agua.2148
Rev. Ambient. Água vol. 15 n. 2, e2368 - Taubaté 2020
14 Willames Albuquerque Soares et al.
SOUZA, E. S.; ANTONINO, A. C. D.; NETTO, A. M.; SOUZA, R. M. S.; GONDIM, M. V. S.; LIMA, V. F.; LIMA, J. R. S.; ALVES, E. M.; COUTINHO, A. P.; SOARES, W. A. Hydrodynamic behavior of soils in recession agriculture in semiarid of Pernambuco State (Brazil). Journal of Environmental Analysis and Progress, n. 1, p. 52-60, 2016. https://dx.doi.org/10.24221/jeap.1.1.2016.984.52-60 VAN GENUCHTEN, M. Th. A closed-form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Science Society of America Journal, n. 44, p. 892–898, 1980. https://dx.doi.org/10.2136/sssaj1980.03615995004400050002x WHITE, I.; SULLY, M. J. Macroscopic and microscopic capillary length and time scales from field infiltration. Water Resources Research, v. 23, p. 1514-1522, 1987. https://doi.org/10.1029/WR023i008p01514
Rev. Ambient. Água vol. 15 n. 2, e2368 - Taubaté 2020
Ambiente & Água - An Interdisciplinary Journal of Applied Science ISSN 1980-993X – doi:10.4136/1980-993X www.ambi-agua.net E-mail: [email protected]
Sustainable provision of raw water based on the management of ecosystem services in small watersheds
ARTICLES doi:10.4136/ambi-agua.2439
Received: 05 Jul. 2019; Accepted: 26 Jan. 2020
Mateus Marques Bueno1* ; Ricardo Valcarcel2 ; Marcos Gervasio Pereira3 ; Felipe Araújo Mateus2
1Departamento de Agronomia. Instituto Federal de Educação de Minas Gerais (IFMG/SJE), Avenida Primeiro de Junho, n° 1043, CEP: 39705-000, São João Evangelista, MG, Brazil. 2Departamento de Ciências Ambientais. Instituto de Florestas. Universidade Federal Rural do Rio de Janeiro (UFRRJ), Rodovia BR 465, Km 07, s/n, CEP: 23890-000, Seropédica, RJ, Brazil. E-mail: [email protected], [email protected] 3Departamento de Solos. Instituto Agronomia. Universidade Federal Rural do Rio de Janeiro (UFRRJ), Rodovia BR 465, Km 07, s/n, CEP: 23890-000, Seropédica, RJ, Brazil. E-mail: [email protected] *Corresponding author. E-mail: [email protected]
ABSTRACT The differentiated effects of the provision of environmental services in a watershed are due to the capacity of regularization of outflows in its mouth. In impacted areas, this environmental function is affected, and in some situations, it ceases to exist completely. This study characterized the soil and the production of sediments in anthropic watersheds, with the purpose of describing and evaluating the environmental services offered by a watershed undergoing anthropic transformation. The analyses show that the water flow in the remaining watersheds was preferably horizontal in the transmission zone, and these areas represent almost all areas. The values of hydraulic conductivity suggest that the infiltration decreases with soil depth; this fact is corroborated by the values of bulk density. The natural regions of water accumulation, the floodplains or outcrops zones, are small and do not have direct contact with the main floodplain present in the Guandu River Basin, making it impossible to recharge through other areas. Even so, water balance shows that the set of measures implemented ensured that the deficit water demand was supplied during the years of operation, even in times of water deficit. Likewise, the retention of solids in the settling tanks and in the drainage system prevented some 29,000 t of sediment from being carried between the years of 2012 and 2015.
Keywords: hydric balance, sediments, water resources. Produção sustentável de água bruta baseado no manejo dos serviços ecossistêmicos de microbacias
RESUMO Os efeitos diferenciados da produção de serviços ambientais em microbacias se devem à capacidade de regularização das vazões de saída em seu exutório. Já em áreas impactadas esta função ambiental é afetada e, em algumas situações, deixa de existir completamente. Este estudo objetivou caracterizar o solo e a produção de sedimentos em microbacias antropizadas, com o intuito de descrever e avaliar os serviços ambientais oferecidos por uma bacia em transformação antrópica. As análises mostram que o fluxo hídrico nas microbacias remanescentes eram, preferencialmente, horizontais na zona de transmissão, que representa
This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
2 Mateus Marques Bueno et al. quase a totalidade das áreas. Os valores de condutividade hidráulica, sugerem que a infiltração diminui em profundidade, este fato é corroborado pelos valores de densidade do solo. As regiões naturais de acúmulo de água, as várzeas ou zonas de afloramento, são pequenas e não possuem recarga por outras áreas. Mesmo assim, balanço hídrico mostra que o conjunto de medidas implementadas garantiu que a demanda hídrica deficitária fosse suprida ao longo dos anos de funcionamento, mesmo em época de déficit hídrico. Da mesma forma, a retenção de sólidos nos tanques de decantação e no sistema de drenagem, impediu que cerca de 29.000 t de sedimentos fossem carreados entre os anos de 2012 a 2015.
Palavras-chave: balanço hídrico, recursos hídricos, sedimentos. 1. INTRODUCTION The differentiated effects of the pro environmental services in watersheds, because of the hydrologically sensitive effects, can be measured by their ability to regularize the flow of the river basin. Under natural conditions, the watersheds have the capacity to produce water, thus contributing to the sustainable development of their environment. They control the exchange of water and related chemical flows from the upper catchment area to surface waters like streams and lakes (Hattermann et al., 2006). In impacted areas, the ecosystem function of water provision can be affected, depending on the type of use and the intensity of that use, as well as the modifications of the soil attributes. Commonly, water is produced in the flat and high areas of watersheds and stored in outcrop areas or natural reservoirs. These reservoirs may present small individual capacity; however, when all the contributions are united, the local water regime is created. Barban (2009) argues that natural reservoirs must be interrelated and, therefore, they must be appropriately interlinked with sectoral policies established by the government water management practices. Thus, the diagnosis of the conditions of the small watersheds and the impacts they endure should guide the measures to provide water. This differentiation is due both to the large amplitude in the precipitated volume during the year and to the effect of the sea and rivers, especially in the lowlands. In this sense, the irregular exploitation of the soil, combined with the increase in temperature and the irregular distribution of rainfall, increase the variation of water production capacity within the same watershed (Gnadlinger, 2014). In addition, the correct identification of key elements of watershed ecosystems services allows a series of measures to be applied in order to enhance a desired service, such as water production. This correct identification will guarantee the increase of water storage inside the watershed and, consequently, the reduction of surface water loss. In this way, the integrated management of watersheds and ecosystems, although distinct, must converge towards the same end (Cook and Spray, 2012). Therefore, the provision of water in a watershed depends on the natural capacity of the area and local climate, but it is possible that occasional changes may increase this capacity. This study was developed in a small group of watersheds, where an industrial project with high demand for water resources is leased, with a low capacity to offer them naturally. The study characterized the soil and the production of sediments in the watershed, in order to describe and evaluate the environmental services offered by a watershed undergoing anthropic transformation. 2. MATERIALS AND METHODS The study (Figure 1) was carried out in a Group of Small Watersheds (GMH), which were classified as watersheds not only for their size, but also for their hydrological functions,
Rev. Ambient. Água vol. 15 n. 2, e2439 - Taubaté 2020
Sustainable provision of raw water based on … 3 especially the characteristic of allowing the measurement of actions in their area, such as heavy rainfall and changes in soil cover (Teodoro et al., 2007). There is mining in operation in these areas. The total area of the watersheds is 73.37 ha. This area was in the eastern center portion of the Guandu System (BHSG), in Queimados, RJ. The central coordinate of the study area is 22°43'49.82" S and 43°32'43.87" W.
Figure 1. Location of Guandu Watershed System (BHSG) and the Small Watersheds (GMH) were ecosystem management actions were carried out.
The predominant climate in the region is Aw de Köppen (Alvares et al., 2013). The rainfall regime is characterized by a rainy season, from December to March (summer), and dry season, from June to August (winter). The average annual precipitation is 1,270 mm; however, the configuration of the relief, given that the GMH are located at the northwest of the geographic mass called Madureira Mendanha, combined with the predominant air currents (Atlantic tropical - mTa), make the average rainfall lower in this area than it is in the BHSG. Local rainfall, temperature and wind speed data were obtained from an ION-1090-WH meteorological station installed in the experimental area. The total annual average precipitation for the station installed in the experimental area and in the year 2016 was 700 mm. The activity developed in this study is the complete transformation of the landscape, removing all soil demand, as well as the rocks, which are processed using water. The flow demanded by the production system depends on the volume of production and the climatic conditions. Thus, higher water demand occurs when there is a lower supply, which is during the dry season. On average, the daily consumption projected for the entire production system, running 24 hours a day, is 40 m3 of water. With respect to water provision, the ecosystem service offered in the study area is restricted to small areas of outcrop, as related by Bueno et al. (2019). Thus, water supply and sediment production were applied by means of a water balance and by measuring the volume of sediment that left the system. In addition, the water-flow pattern was described in the different hydrogenetic zones, as proposed by Bueno et al. (2019), through the local relief and description of soil profiles. In general, environmental service-enhancing practices were aimed at reducing evapotranspiration losses and increasing the volume of water in the subsurface aquifer, in addition to allowing the circulation of the water surplus. This system allowed the precipitated water to be directed to the outcrop areas and stored. Subsequently, part of this volume was pumped into a passing box system, then transferred to an Australian tank where it was then Rev. Ambient. Água vol. 15 n. 2, e2439 - Taubaté 2020
4 Mateus Marques Bueno et al. used. Finally, the unused portion was returned to the drainage system, returning to the storage system. The total period of study was from 2011 to 2016. In 2011, secondary data were collected to prepare the initial water balance, to diagnose the study area before the start of mining activities. In the following years, 2012 to 2014, the implantation and evaluations of the mitigating measures were carried out. The field tests and analyses, described in the sequence, were carried out in the years of 2015 and 2016. The GMH morphometric characterization was based on physiographic parameters and drainage patterns classified according to Christofoletti (1980). The physical parameters of the GMH (area, perimeter, channels’ lengths, drainage density, form factor, index of circularity [Ke], compactness index [Kc], and sinuosity index [Is]) were computed as described by the methodology of Hajam et al. (2013). The database, with the available environmental information (elevation data, political and geographic boundaries, thematic maps, satellite images) was obtained through the processing of the digital cartographic base from the Brazilian Institute of Geography and Statistics (IBGE), with equidistant 10 m level curves, hydrography and quoted points, at the 1: 25,000 scale. The GMH soil characterization was made in the remaining areas (out of the mining pit), in the hydrogenetic zones named: capitation, transmission and outcrop. At these points, trenches were opened to describe soil profiles and the collection of deformed samples with dutch traces was carried out and the samples were collected using the Uhland collector. The depths of samples were: 15 cm, 40 cm and 70 cm. For each collection point, 3 replications were performed. In the laboratory, the chemical and granulometric characterization was carried out according to Donagema et al. (2011). The hydraulic conductivity measurement was performed through a constant-load permeameter. The macro- and micro porosity were determined by means of the tension table, and the soil bulk density was determined using the volumetric balloon method of Donagema et al. (2011). In addition, the measurement of soil depth was evaluated along the remaining areas and progress of the soil in order to qualify the storage capacity and the predominant water flows. Soil water storage systems were constructed in each of the watersheds. These areas, with functions like outcrop zones, were maintained and potentialized through the construction of underground dams. In the center of each storage area was constructed a shallow well, from which the water was collected, initially destined for a reservoir, and later, for different uses. This measure allied to the drainage system allows the circulation of water in the system. The runoff flow was obtained from the measurement of the maximum height values of the drainage channel and correlation with the catchment area, individually for each small watershed, and added to obtain the total flow of the GMH. The total volume of sediments of lower particle size was obtained by multiplying the mean sediment concentration and estimated total flow. Throughout the drainage and water storage system, small sedimentation wells were designed, and at strategic points, larger wells, in order to facilitate the infiltration of water into the soil. Whenever possible this system was in contact with the original terrain, pouring water infiltrated to the natural drainage of the small watersheds. The quantity of sediments that leave the system was measured by the undisturbed collection of sediments samplers, adapted by FIASP (1966), installed in the outcrop of the watersheds. For each measurement point, 4 samplers were installed per height, which consisted of repetitions. The sediment concentration considered was the average of the repetitions per height. The collections were made after precipitation in the study area above 12 mm. Eight collectors were installed along the exit of the last sedimentation tank. The first sampling line corresponded to the minimum tank dimension and the second 0.1 m above. In the laboratory, the samples were weighed and carried to the oven at 105ºC for 24 h, obtaining the mass of
Rev. Ambient. Água vol. 15 n. 2, e2439 - Taubaté 2020
Sustainable provision of raw water based on … 5 sediments. These samples were accumulated, quantified and their granulometric composition were analyzed according to Donagema et al. (2011). The statistical design used was completely randomized and the results obtained were submitted to the normal analysis of the error distribution and homogeneity of error variances in computer environment R,Version 3.5.1 (R Core Team, 2018). The environmental services quantified in this study are related to water provision and sediment retention in the system. The quantification of the water provision was carried out through the climatological water balance of the small watersheds, the measured water demand and the quantification of the volumes of water stored in the system. The sediment quantification was based on the sediment-concentration data at sedimentation basins. The results of hydraulic conductivity, porosity and density were used as indicators of the initial condition of the land with respect to water provision. 3. RESULTS AND DISCUSSION The GMH altimetric heights range from 40 to 200 m, the slope is between 45 to 75% (mountainous relief). The flat areas add 2.7 ha of total area. The surface of flat curvature is predominant in 15% of the total area, the rest being dominated by the convex surface, with 62%, followed by the concave, with 23%. In the same way, the orientation of the slopes is variable, but with preponderance of the South and East faces. The hydrogenetic transmission zone represents 68% of the GMH, followed by the capitation zone (20%) and outcrop zone (12%). Teodoro et al. (2007) states that the morphometric parameters of the watershed can be used as indicators of water flows and, consequently, the capacity of natural accumulation of water in the soil. The Dd indicates the drainage system efficacy (Rai et al., 2017), and represents the inverse relation of river length, where high values of drainage density are related to the small length of contributing tributaries. The average Dd of GMH and selected micro-basins was 2.2 km/km² showing medium drainage. In this way, the studied watersheds have a predominance of horizontal flow and low capacity for water accumulation within the system. These results show that the area has a low natural water provision capacity, given that the watershed predominantly tends to flow superficially with the volume of precipitation received. This result agrees with that found by Bueno et al. (2019) who used the topographic index of humidity as indicator of water-producing areas and concluded that the study area has a low capacity for water provision. The studied soil profiles presented relatively shallow surface horizons (10 to 15 cm), with subsurface horizons with slow permeability and some profiles with close contact to the surface. The morphological, chemical and physical attributes of the profiles show that, in the hydrogenetic zones of capitation and transmission, there is occurrence of Oxisol (Latossolo Amarelo) (Santos et al., 2018). In addition, there is the presence of horizontal water flow due to the layer of impediment. In the outcrop zone, a Ultisols (Planossolo Nátricos) (Santos et al., 2018) was identified, resulting from the action of artificial drainage. The mean total organic carbon values, in kg-1, were 4.94, 3.22, and 3.9, respectively, for capitation, transmission and outcrop zones. These values suggest that the whole area had low levels of organic matter, before the mining pit was dug. In addition, the low nutrient content is detrimental to the development of vegetative cover in deposition areas, which could act as a buffer to the direct impact of raindrops on the soil surface. This impact, with the subsequent destruction of the aggregates and their individualization, can cause superficial sealing of the surface layer, reducing the rate of infiltration of water in the soil and increasing the amount of sediments carried through surface runoff (Gonçalves and Moraes, 2012). A significant difference was observed for the saturated hydraulic conductivity (CHS), at 5% probability by the t test, while for the soil density and porosity no differences were observed Rev. Ambient. Água vol. 15 n. 2, e2439 - Taubaté 2020
6 Mateus Marques Bueno et al. in the hydrogenetic zones (Table 1). In the capitation and transmission zone, there was a reduction of 34 and 90% in the value of CHS, indicating the prevalence of horizontal flows of water in the soil, or subsurface flow. The hydraulic conductivity can be considered as the ease with which the soil transmits water (Freitas et al., 2007), this way it is evident that the water flow tends to become horizontal flow. This fact is corroborated by the values of soil density that increase in depth and by the presence of pipes and horizons in which there is a lower hydraulic conductivity and layers of impediment, identified in the soil profile analysis.
Table 1. Soil hydraulic conductivity means for the different hydrogenetic zones and at three different depths. Soil hydraulic conductivity * (mmh-1) Soil depths (cm) hydrogenetic zones 15 40 70 Capitation 134.60 aA 144.06 aA 88.77 aA Transmission 287.40 aA 101.14 aB 29.10 aB Outcrop 52.40 bA 34.20 aA 103.32 aA *Values followed by different letters, lowercase in the column and upper case in the row, indicate that the values differ from each other (p <0.05), by the test of t and ns: not significant.
Thirteen km of drainage channels were mapped, followed by small sedimentation tanks, which directed the rainwater to the 11 main sedimentation tanks. Seven floodplain areas were mapped, with total storage capacity of up to 141,750 m3 of water. Considering the average density value proposed by Falcão and Ayres Neto (2010), the set of sedimentation tanks for the years 2012 to 2015 retained about 29,000 Mg of sediment in the system. This result shows the efficiency of the measurement, which was also confirmed through the qualitative analysis of the effluent leaving the system. The highest sediment concentration values (Table 2) measured in the river basin of the GMH were observed at the spillway level. Regarding the horizontal variation, the highest value was quantified in the central sampler. When analyzing the interaction between the mean sediment concentration and the value of the precipitated leaf in each sampling period, no significant differences were observed. The total sediment mass values for the samples were 13.91 kg, 13.60 kg, 20.04 kg, 13.74 kg and 43.94 kg, respectively. These data show that, even in a period of full soil movement, the sediment export is very low and does not depend on precipitation volume. The granulometric distribution of the solid sediments (Figure 2) varied in the direction of the inlet to the exit of the sedimentation tanks, and the sedimentation wedges near the entrance had wider diameters than those near the tank exudation. This pattern is due to the energy lost by the particles when being transported. As the energy decreases, the larger diameter particles begin to be deposited closer to the tank entrance, while the smaller ones are transported for longer distances (Palanques et al., 2009). Similarly, the horizontal distribution of the sediments may be correlated with the intensity of the rains, since the tanks receive sediments throughout the year, being emptied only in the dry period. The visual analysis of the solid fraction of the sediments shows that they are mostly composed of primary minerals, highlighting the low values of total organic carbon in all layers. These results suggest that most of the accumulated sediment comes from the plowing area, in which there is constant movement of land.
Rev. Ambient. Água vol. 15 n. 2, e2439 - Taubaté 2020
Sustainable provision of raw water based on … 7
Table 2. Concentration of fine sediments, in g L-1, for the 5 field collections. Concentration of fine sediments *, in gL-1 Localization Mean 1 2.04 c 2 2.30 b 3 2.64 a 4 2.34 b Height Mean 1 3.22 a 2 1.44 b **Values followed by different letters, lowercase in the column and upper case in the row indicate that the values differ from each other (p <0.05), by the test of t.
Figure 2. Percentage of variation of the diameter of the sediments accumulated along the sedimentation wedges of the tank. Sample block A represents the collection points closest to the tank inlet, B represents the center points and C the points closest to the tank outlet. The actual water demand for the years 2012 to 2014 (Figure 3) shows a progressive increase over the years. The final balance of water provision in the GMH (Table 3) shows that there was supply of demand, even in periods when the climatological water balance was negative, in 2014.
Figure 3. Water demand measured for the years 2012 to 2014, in m3.
Rev. Ambient. Água vol. 15 n. 2, e2439 - Taubaté 2020
8 Mateus Marques Bueno et al.
Table 3. Final balance of water provision before and after the implementation of the measures that empower environmental services. Item (m3) 2011 2012 2013 2014 Climatological water balance -129.813,99 7,222.18 243,801.22 -219,735.00 Storage capacity - 227,333.00 238,699.65 281,892.92 Precipitation 709,194.42 875,157.36 1,082,207.50 685,275.80 Capture for industrial use - 7,355.60 28,153.00 50,567.00 Final balance -129,813.99 227,199.58 454,347.87 11,590.92
The final balance shows that the potential evapotranspiration is greater than the precipitated blade for the years 2011 and 2014; meanwhile, in 2012, these values are practically the same. Thus, in normal conditions, the GMH would not have the capacity to supply water for the activities developed, even considering the use of all precipitated water, which would not support industrial activity. However, the installed water collection, storage and distribution system shows that there was an inversion of the natural tendency of the water flow, allowing rainwater to remain in the system for longer and reducing water volume loss through evapotranspiration. In this way, actions should be directed towards ecosystems capable of improving the use of water resources, allowing the feasibility of the proposed activities, promoting the economic and social development of areas that, due to lack of water, would not have this capacity. The environmental services offered by a watershed in an anthropic transformation process are related to the maintenance of positive water balance and sediment retention in the system.
4. CONCLUSIONS
The studied watersheds demonstrate low natural capacity to provincial environmental services related to water resources. The continuous and irregular use of the area has decreased water availability in these areas. Consequently, the climatic water balance is negative, since the potential evapotranspiration is greater than or equal to the precipitated leaf. The identification of areas with water storage capacity and recirculation processes allowed the resource to remain in the system, contributing to the environmental and economic feasibility of the proposed activities. Therefore, a model of water production and sediment contention, based on the identification of the mature ecosystems and the implementation of a system of abstraction, directing and subsurface storage of rainwater and recirculation of surpluses, has proven to be efficient and can be used as an important tool management of environmental services.
5. ACKNOWLEDGEMENTS
We thank the Federal Rural University of Rio de Janeiro, specifically the PPGCAF, LMBH and LGCS. We recognize CNPq and the Petra Agregados mining company for the financial support. This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001.
6. REFERENCES
ALVARES, C. A.; STAPE, J. L.; SENTELHAS, P. C.; DE MORAES, G.; LEONARDO, J.; SPAROVEK, G. Köppen's climate classification map for Brazil. Meteorologische Zeitschrift, v. 22, n. 6, p. 711-728, 2013. https://doi.org/10.1127/0941-2948/2013/0507
Rev. Ambient. Água vol. 15 n. 2, e2439 - Taubaté 2020
Sustainable provision of raw water based on … 9
BARBAN, V. Fórum Mundial da Água–questões fundamentais e muitas controvérsias. REDD– Revista Espaço de Diálogo e Desconexão, v. 1, n. 2, 2009. BUENO, M. M.; VALCARCEL, R.; MATEUS, F. A.; PEREIRA, M. G. Environmental services in watersheds with small declivity: fluvial marine plains. Revista Ambiente & Água, v. 14, n. 3, p. 1-11, 2019. https://doi.org/10.4136/ambi-agua.2265 CHRISTOFOLETTI, A. Geomorfologia. 2. ed. São Paulo: Edgard Blücher, 1980. 188 p. COOK, B. R.; SPRAY, C. J. Ecosystem services and integrated water resource management: Different paths to the same end? Journal of Environmental Management, v. 109, p. 93-100, 2012. https://doi.org/10.1016/j.jenvman.2012.05.016 DONAGEMA, G. K.; CAMPOS, D. D.; CALDERANO, S. B.; TEIXEIRA, W. G.; VIANA, J. H. M. Manual de métodos de análise de solos. Rio de Janeiro: Embrapa Solos, 2011. 230 p. FALCÃO, L. C.; AYRES NETO, A. Parâmetros físicos de sedimentos marinhos superficiais da região costeira de Caravelas, sul da Bahia. Revista Brasileira de Geofísica, v. 28, n. 2, p. 279-289, 2010. https://doi.org/10.1590/S0102-261X2010000200011 FIASP. A study of methods used in measurement and analysis of sediment loads instreams. Minnesota: Anthony Falls Hydraulic Lab. Minneapolis, 1966. FREITAS, M. D. G. B.; MESQUITA, S. O. M.; PERUCHI, F.; DE CARVALHO TEREZA, M. Alternativa para caracterização da condutividade hidráulica saturada do solo utilizando probabilidade de ocorrência. Ciência e Agrotecnologia, v. 31, n. 6, 2007. https://doi.org/10.1590/S1413-70542007000600001 GNADLINGER, J. How can rainwater harvesting contribute to living with droughts and climate change in semi-arid Brazil? Waterlines, v. 33, n. 2, p. 146-153, 2014. www.jstor.org/stable/24688145 GONÇALVES, F. C.; MORAES, M. H. Porosidade e infiltração de água do solo sob diferentes sistemas de manejo. Irriga, v. 17, n. 3, p. 337, 2012. https://doi.org/10.15809/irriga.2012v17n3p337 HAJAM, R. A.; HAMID, A.; BHAT, S. Application of morphometric analysis for geohydrological studies using geo-spatial technology - A case study of Vishav drainage watershed. Hydrology Current Research, v. 4, n. 3, p. 1-12, 2013. http://dx.doi.org/10.4172/2157-7587.1000157 HATTERMANN, F. F.; KRYSANOVA, V.; HABECK, A.; BRONSTERT, A. Integrating wetlands and riparian zones in river basin modelling. Ecological modelling, v. 199, n. 4, p. 379-392, 2006. https://doi.org/10.1016/j.ecolmodel.2005.06.012 PALANQUES, A.; PUIG, P.; LATASA, M.; SCHAREK, R. Deep sediment transport induced by storms and dense shelf-water cascading in the northwestern Mediterranean basin. Deep Sea Research Part I: Oceanographic Research Papers, v. 56, n. 3, p. 425-434, 2009. https://doi.org/10.1016/j.dsr.2008.11.002 RAI, P. K.; MOHAN, K.; MISHRA, S.; AHMAD, A.; MISHRA, V. N. A GIS-based approach in drainage morphometric analysis of Kanhar River Basin, India. Applied Water Science, v. 7, n. 1, p. 217-232, 2017. https://doi.org/10.1007/s13201-014-0238-y R CORE TEAM. R: a language and environment for statistical computing. Vienna: R Foundation for Statistical Computing, 2018. Rev. Ambient. Água vol. 15 n. 2, e2439 - Taubaté 2020
10 Mateus Marques Bueno et al.
SANTOS, H. G. dos et al. Sistema Brasileiro de Classificação dos Solos. 5. ed. Brasília: Embrapa, 2018. 356 p. TEODORO, V. L. I.; TEIXEIRA, D.; COSTA, D. J. L.; FULLER, B. B. O conceito de bacia hidrográfica e a importância da caracterização morfométrica para o entendimento da dinâmica ambiental local. Revista Brasileira Multidisciplinar, v. 11, n. 1, p. 137-156, 2007. https://doi.org/10.25061/2527-2675/ReBraM/2007.v11i1.236
Rev. Ambient. Água vol. 15 n. 2, e2439 - Taubaté 2020
Ambiente & Água - An Interdisciplinary Journal of Applied Science ISSN 1980-993X – doi:10.4136/1980-993X www.ambi-agua.net E-mail: [email protected]
Heavy metals in soils and forage grasses irrigated with Vieira River water, Montes Claros, Brazil, contaminated with sewage wastewater
ARTICLES doi:10.4136/ambi-agua.2440
Received: 11 Jul. 2019; Accepted: 06 Feb. 2020
Matheus Mendes Reis1* ; Leonardo David Tuffi Santos2 ; Ariovaldo José da Silva1 ; Gevany Paulino de Pinho2 ; Leonardo Michel Rocha2
1Faculdade de Engenharia Agrícola. Universidade Estadual de Campinas (UNICAMP), Avenida Cândido Rondon, n° 501, CEP: 13083-875, Campinas, SP, Brazil. E-mail: [email protected] 2Instituto de Ciências Agrárias. Universidade Federal de Minas Gerais (UFMG), Avenida Universitária, n°1000, CEP: 39404-547, Montes Claros, MG, Brazil. E-mail: [email protected], [email protected], [email protected] *Corresponding author. E-mail: [email protected]
ABSTRACT There is great concern with soil and plant contamination by heavy metals due to the use of polluted water in agricultural irrigation. In this study, areas irrigated with Vieira River water were evaluated as to contamination by As, Cr, Cu, Ni, Pb and Zn. The Vieira River receives effluent from Montes Claros city, state of Minas Gerais, Brazil. To do so, two irrigated areas were selected, one upstream and one downstream of the Montes Claros city. Wastewater discharge increased the concentration of As and Ni in the water of Vieira River, and consequently, of As, Cr, Cu, Ni, Pb and Zn in the soil and of As and Zn in forage grasses. However, the content of heavy metals in the soil did not exceed the internationally recommended limits. Pollution load index (PLI) and contamination factor (CF) indicated the existence of pollution and moderate contamination in downstream soils of the city of Montes Claros. Potential ecological risk index (RI) and ecological risk factor (Er) indicated a low ecological risk, but these indicators were higher in downstream soils of Montes Claros. Arsenic (As) was the only heavy metal that featured a transfer factor (TF) higher than the widespread values found in literature and positive geoaccumulation index (Igeo), indicative of anthropogenic pollution.
Keywords: ecological risk, geoaccumulation index, water contaminated. Metais pesados em solos e plantas forrageiras irrigadas com água do Rio Vieira, Montes Claros, Brasil, contaminada com efluentes de esgoto
RESUMO A contaminação de solo e plantas por metais pesados devido ao uso de águas poluídas na irrigação agrícola é motivo de grande preocupação. No presente estudo, áreas irrigadas com água do rio Vieira foram avaliadas quanto a contaminação por As, Cr, Cu, Ni, Pb e Zn. Para isso foram selecionadas duas áreas, uma a montante e outra a jusante da cidade de Montes Claros. A descarga de água residuária aumentou a concentração de As e Ni na água do rio
This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
2 Matheus Mendes Reis et al.
Vieira; e, consequentemente, de As, Cr, Cu, Ni, Pb e Zn no solo; e de As e Zn em plantas forrageiras. No entanto, os teores de metais pesados no solo não excederam os limites internacionais recomendados. O índice de carga de poluição (PLI) e o fator de contaminação (CF) indicaram existência de poluição e contaminação moderada em solos a jusante da cidade de Montes Claros. O índice de risco ecológico potencial (RI) e o coeficiente de risco ecológico (Er) indicaram baixo risco ecológico, porém esses indicadores foram maiores no solo a jusante de Montes Claros. O As foi o único metal pesado que apresentou fator de transferência (TF) maior que os valores generalizados encontrados na literatura e índice de geoacumulação (Igeo) positivo, indicativo de poluição antropogênica.
Palavras-chave: água contaminada, índice de geoacumulação, risco ecológico. 1. INTRODUCTION
The dispersal of heavy metals in irrigated agricultural areas is growing, which results in food contamination that can be harmful for animals and humans. Heavy metals have low solubility, and are not degradable in water, which contributes to their accumulation in soil, and therefore in plants cultivated on these irrigated areas with contaminated water. Heavy metals’ transfer from soils to plants is one of the main ways of humans exposure through the food chain (Chopra and Pathak, 2015). Until 2010, Vieira River was the main river receiving untreated sewage produced in the city of Montes Claros, state of Minas Gerais, Brazil. Currently, the river still receives city sewage; however, there is a prior treatment process, carried out in the wastewater treatment plant (WWTP) of Montes Claros. In the margins of Vieira River, there are farms that use its water for the irrigation of pastures; nevertheless, there are no studies on heavy metal contamination of soil and plants irrigated with the river water. The intake of heavy metals through the food chain has been widely disseminated throughout the world (Chary et al., 2008; Chopra and Pathak, 2015). Heavy metals are non- biodegradable and persistent compounds, which, because of these characteristics, accumulate in vital organs of the human body, such as kidneys, bones and liver, and are associated with several serious health disorders, such as diarrhea, stomatitis, tremor, ataxia, paralysis, convulsion, depression, and pneumonia (McCluggage, 1991). The nature of the effects of these disorders can be toxic, neurotoxic, carcinogenic, mutagenic, or teratogenic (EU, 2002). This study assessed the concentration of As, Cr, Cu, Ni, Pb, and Zn in water, soil, and forage grasses in areas irrigated with Vieira River water.
2. MATERIALS AND METHODS
2.1. Study area The study area is located in the city of Montes Claros, Brazil, in the North of the state of Minas Gerais. The climate of the region is classified, according to Köppen, as Aw. Vieira River is the main receiver of wastewater of domestic and industrial sewage of Montes Claros. Vieira River rises in the south of Montes Claros and flows through residential and industrial areas before joining Verde Grande River, one of the main affluents of the middle region of the São Francisco River Basin. The length of the main course of Vieira River and the area of its basin is approximately 42 km and 580 km2, respectively. The Wastewater Treatment Plant (WWTP) is located in Northern Montes Claros (Figure 1). Several industry plants are located west of the WWTP (Figure 1), including textile, biofuels, food, pharmaceutical, and mining industries. About 1 km east of the WWTP, there is another textile factory (Figure 1).
Rev. Ambient. Água vol. 15 n. 2, e2440 - Taubaté 2020
Heavy metals in soils and forage grasses … 3
Figure 1. Location map of the study area.
The unpleasant odor and presence of solid residues and white foam in waters of Vieira River are easily observed in stretches passing through Montes Claros and downstream of WWTP.
2.2. Sample collection To evaluate levels of contamination by heavy metals in areas irrigated with Vieira River water, samples of water, soil, and plants were collected at two farms (sites F1 and F2 in Figure 1) in July 2015. The F1 farm is located upstream of the city of Montes Claros and uses Vieira River water for irrigation of forage grasses (Pennisetum purpureum), and the irrigation system used is the sprinkler. The F2 farm is located downstream of the city of Montes Claros and diverts part of the Vieira River water to an area of flood irrigation, which cultivates forage grasses (Brachiaria mutica) for feeding the cattle of milk producers. Samples of unfiltered water of the river were collected approximately 10 m from the margin, where the water used in irrigation is collected. The water samples were stored in polypropylene bottles that had been previously washed with HNO3 (10%). To preserve the water samples, about 1.5 mL of HNO3 (65%) was added to reduce their pH to values lower than 2. Sampling bottles were kept in coolers with ice during their transportation to the laboratory, where they were stored in a refrigerator at temperatures between 0 and 4°C until the quantification of heavy metals (APHA et al., 1998). At each farm (F1 and F2), eight sites were selected for the collection of samples of soil and forage grasses (Figure 1). Each sample was composed of three subsamples collected in an area of 1 m². Samples were placed in plastic bags and sealed for transportation and storage (Gebrekidan et al., 2013). Soil samples were collected in the 0-20 cm layer. In the laboratory, samples were dried in an oven at 60°C for 72 hours, homogenized in an agate mortar and pistil, and sieved in a Nylon sieve of 0.3 mm. In the samplings of plant material, the plants were cut to 4 cm from the ground. In the laboratory, samples were washed with tap water and distilled water for removing particulate material deposited on the surface of the plant. Then, all samples were dried in an oven at 75°C
Rev. Ambient. Água vol. 15 n. 2, e2440 - Taubaté 2020
4 Matheus Mendes Reis et al. until constant weight, grinded, and sieved (Nylon sieve of 0.3 mm). The sieved soil and plant samples were stored in Falcon tubes for further analysis of heavy metal content.
2.3. Chemical analysis The stock standard solution of 1000 mg L-1 for atomic absorption spectroscopy of Sigma Aldrich (Germany), diluted in different concentrations with ultrapure water (Milli-Q, Millipore), was used for the preparation of analytical curves. Cr, Cu, Ni, Pb, and Zn elements were measured in flame atomization mode, composed of Ar-acetylene (acetylene 2.8 AA), and the As element was determined by a hydride generator system using argon (99.999% purity) and Ar-acetylene (acetylene 2.8 AA) (APHA et al., 1998). All analyses were performed in triplicate. For total metal analysis, 100 mL of the water sample was mixed with 10 mL of HNO3 (65%, PA) and taken to a hot plate, in which it was evaporated to a volume from 10 to 20 mL (APHA et al., 1998). Digested samples were then filtered through a quantitative filter paper (Unifil, C42, blue stripe) and transferred to Falcon tubes. The volume of each sample was adjusted to 25 mL using ultrapure water (Milli-Q, Millipore). Concentrations of As, Cr, Cu, Ni, Pb, and Zn were determined in an atomic absorption spectrophotometer (Varian, AA 240 FS model). For soil digestion, 0.50 g of each sample was mixed to 9 mL of HNO3 (65%, PA) and 3 mL of HCl (37%) and microwave digested (Mars 6, CEM) according to the USEPA 3051A method (USEPA, 1998). In the case of forage grasses, 0.01 g of each sample was mixed with 10 mL of HNO3 (65%, PA) and digested in a similar way to the soil samples. After the digestion process, soil and plant samples were then filtered through a quantitative filter paper (Unifil, C42, blue stripe) and diluted with ultrapure water (Milli-Q, Millipore) until it reached a volume of 25 mL. Concentrations of As, Cr, Cu, Ni, Pb, and Zn were determined in an atomic absorption spectrophotometer (Varian, AA 240 FS model).
2.4. Indicators and Statistical analysis To understand the impact of heavy metals present in the soil, the following were calculated: contamination factor (CF) (Equation 1); pollution load index (PLI) (Equation 2); geoaccumulation index (Igeo) (Equation 3); and potential ecological risk index (RI) (Equation 4). Assessment of contamination level by heavy metals using these factors has been successfully employed in several studies (Varol, 2011; Wang et al., 2018).
퐶 퐶퐹 = ℎ푒푎푣푦 푚푒푡푎푙 (1) 퐶푏푎푐푘𝑔푟표푢푛푑
CF is the ratio between each metal content in soil samples and the background value. The adopted background values were 0.23 mg kg-1 for As (Kabata-Pendias and Pendias, 1999); 35.00; 25.00; 20.00; and 20.00 mg kg-1 for Cr, Cu, Ni, and Pb, respectively (Taylor and McLennan, 1995); and 49.50 mg kg-1 for Zn (Turekian and Wedepohl, 1961). Interpretation of CF values was suggested by Hakanson (1980), according to which CF < 1 indicates low contamination; 1 < CF < 3 indicates moderate contamination; 3 < CF < 6 indicates considerable contamination; CF > 6 indicates very high contamination.
1 푃퐿퐼 = (퐶퐹1 푥 퐶퐹2 푥 퐶퐹3 푥 … 푥 퐶퐹푛)푛 (2)
Where CF is the contamination factor, and n is the number of metal species. PLI presents a general overview of pollution in each sampling site and also shows the contribution of each
Rev. Ambient. Água vol. 15 n. 2, e2440 - Taubaté 2020
Heavy metals in soils and forage grasses … 5 metal to pollution. PLI < 1 indicates that there is no pollution by heavy metals in the site; however, PLI > 1 indicates that there is pollution (Varol, 2011). Igeo determines metal contamination in soils, comparing current contents with background values (Equation 3).
퐶푛 퐼푔푒표 = [ ] (3) 1.5퐵푛
Where Cn is the n metal concentration in soil samples, and Bn is the background value of the n element. The factor 1.5 is introduced in the equation to minimize possible variation in the background value, which can be attributed to lithospheric effects. The seven categories of the geoaccumulation index are presented as follows: Igeo < 0, practically uncontaminated; 0 ≤ Igeo < 1, uncontaminated to moderately polluted; 1 ≤ Igeo < 2, moderately polluted; 2 ≤ Igeo < 3, moderately to heavily polluted; 3 ≤ Igeo < 4, heavily polluted; 4 ≤ Igeo < 5, heavily to extremely polluted; and Igeo > 5, extremely polluted. RI is a factor used to evaluate the potential ecological risk of heavy metals in soils and was initially proposed by Hakanson (1980) (Equation 4).
n n RI = ∑i=1 Er = ∑i=1 Tr x CF (4)
Where Er is the ecological risk factor of a certain heavy metal and Tr is the toxicity factor of a single metal. Toxicity factors of As, Cr, Cu, Ni, Pb, and Zn were 10, 2, 5, 5, 5, and 1, respectively (Hakanson, 1980). Criteria for the Er classification are: Er < 40, low potential ecological risk; 40 ≤ Er < 80, moderate potential ecological risk; 80 ≤ Er < 160, considerable potential ecological risk; 160 ≤ Er < 320, high potential ecological risk; and Er ≥ 320, very high potential ecological risk (Hakanson, 1980). The RI classification introduced by Hakanson (1980) was based on eight parameters (As, Cd, Cr, Cu, Hg, Pb, Zn, and PCBs). In this study, all these parameters were not evaluated, therefore, the RI classification should be adjusted according to the number of parameters and the ratio of toxicity coefficient of each parameter (Wang et al., 2018). The adjusted RI classification is: RI < 110, low ecological risk; 110 ≤ RI < 220, moderate ecological risk; 220 ≤ RI < 440, considerable ecological risk; and RI ≥ 440, very high ecological risk. For understanding the bioavailability of a heavy metal, was calculated the transfer factor (TF), which in this study was determined by the relationship between the metal content in the shoot of the plants and in the soil (Equation 5) (Gebrekidan et al., 2013).
푀푒푡푎푙 푐표푛푡푒푛푡 𝑖푛 푡ℎ푒 푠ℎ표표푡 표푓 푡ℎ푒 푝푙푎푛푡 푇퐹 = (5) 푀푒푡푎푙 푐표푛푡푒푛푡 𝑖푛 푡ℎ푒 푠표𝑖푙 Analysis of variance (ANOVA) and F-test were conducted at 5% error probability level to verify differences in contamination by heavy metals between upstream (F1) and downstream (F2) of the city of Montes Claros. All statistical analyses were carried out using the R-plus® 3.4.2. software (R Development Core Team, 2017).
3. RESULTS AND DISCUSSION 3.1. Heavy metal contamination in water of Vieira River used in irrigation The concentrations of heavy metals As and Ni were significantly higher (p < 0.01) in the water of Vieira River at the farm margins downstream of the city of Montes Claros (F2), when compared with the water of the river at the farm margins upstream (F1). On the other hand, Cu featured the higher concentration (p < 0.01) in the water of Vieira River at the F1 margins. None of the concentration values of heavy metals found in the two farms (F1 and F2) were higher than the international limits recommended for water use in irrigation (USEPA, 2012;
Rev. Ambient. Água vol. 15 n. 2, e2440 - Taubaté 2020
6 Matheus Mendes Reis et al.
WHO, 2006). However, Cu and Ni exceeded the limits recommended by the Brazilian legislation for the use of water in irrigation (CONAMA, 2009), being Cu in the two farms (F1 and F2) and Ni only in F2 (Table 1). It is important to emphasize that the water can be inappropriate for irrigation and superficial flooding depending on the use and occupation of the soil, once this irrigation method can favor the direct contact of animals and humans with the contaminated water.
Table 1. Concentration of heavy metals (µg L−1) in water samples of Vieira River for irrigation of F1 and F2 farms, and maximum permitted concentration (µg L−1) in water (n = 3). F1 Farm F2 Farm Metals CONAMA (2005) USEPA (2012) WHO (2006) Mean SD Mean SD As (µg L-1) 0.4** 0.09 1.7 0.01 33 100 100 Cr (µg L-1) 0.0 0.00 0.0 0.00 50 100 100 Cu (µg L-1) 82.6** 0.74 19.4 2.61 13 200 200 Ni (µg L-1) 0.0** 0.00 52.3 1.51 25 200 200 Pb (µg L-1) 0.0 0.00 0.0 0.00 33 5000 5000 Zn (µg L-1) 189.1 5.94 197.6 23.25 5000 2000 2000 SD – Standard deviation; and ** (p < 0.01) indicates statistical difference (ANOVA; F-test) between mean values of metals in F1 and F2. 3.2. Heavy metal contamination in soil irrigated with water of Vieira River Contents of As, Cr, Cu, Ni, Pb, and Zn in samples of soil irrigated with water of Vieira River in F2 were significantly higher (p < 0.05) than in F1 (Table 2), which indicates anthropogenic pollution of Vieira River waters, possibly due to the discharge of domestic and industrial wastewater generated in Montes Claros. The highest concentration of As and Ni in water samples collected at F2 (Table 1) also reinforces the indications of anthropogenic pollution of Vieira River waters.
Table 2. Content of heavy metals (mg kg-1), contamination factor (CF), and pollution load index (PLI) in soil irrigated with Vieira River water in two farms (F1 and F2) (n = 8). F1 Farm F2 Farm Maximum allowed Metals Mean SD CF Mean SD CF Ewers (1991) CONAMA (2009) As (mg kg−¹) 0.3 0.05 1.40 0.6** 0.12 2.50 20.0 35.0 Cr (mg kg−¹) 30.5 5.33 0.87 42.5** 5.27 1.21 100.0 150.0 Cu (mg kg−¹) 15.9 4.01 0.64 20.0* 1.73 0.80 100.0 200.0 Ni (mg kg−¹) 5.5 1.53 0.28 15.9** 0.86 0.79 50.0 70.0 Pb (mg kg−¹) 10.2 2.50 0.51 13.7** 2.10 0.69 100.0 180.0 Zn (mg kg−¹) 33.9 6.73 0.69 53.3** 7.97 1.08 300.0 450.0 PLI 0.65 1.06 SD - Standard Deviation; CF - contamination factor; PLI - pollution load index; * (p < 0.05) and ** (p < 0.01) indicate statistical difference (ANOVA; F-test) between mean values of metals in F1 and F2. Contents of heavy metals in the soil of the study area were higher at F2 farm, downstream of the city of Montes Claros, when compared with those reported by Gebrekidan et al. (2013) for Cr (31.02 mg kg-1), Pb (3.27 mg kg-1), and Zn (51.83 mg kg-1), except Cu (25.25 mg kg-1) and Ni (26.00 mg kg-1) in areas irrigated with water of the Ginfel River, polluted by wastewater produced in Sheba Tannery, Ethiopia. The Cr content reported by Chary et al. (2008) (33.00 ± 12.00 mg kg-1) and by Singh et al. (2010) (19.21 ± 3.26 mg kg-1) was also lower than the mean value found in F2. However, no heavy metal detected in both farms (F1 and F2) featured values
Rev. Ambient. Água vol. 15 n. 2, e2440 - Taubaté 2020
Heavy metals in soils and forage grasses … 7 higher than international and Brazilian limits recommended for soils (CONAMA, 2009; Ewers, 1991) (Table 2). CF values indicated that Cu, Ni, and Pb in both farms (F1 and F2) and Cr and Zn in F1 farm presented low level of contamination. Cr and Zn in F2 and As in both farms (F1 and F2) showed a moderate level of contamination, according to CF (Hakanson, 1980). PLI indicates the existence of heavy-metal pollution in soil irrigated with the water of Vieira River downstream of Montes Claros, despite the its value in F2 being very close to the limit (PLI = 1) that indicates whether or not there is pollution (Varol, 2011) (Table 2). Mean values of geoaccumulation index (Igeo) in the soils of both farms (F1 and F2) accounted for the following descending order: As > Cr > Zn > Cu > Pb > Ni. The As in F2 was the only heavy metal that featured positive Igeo values, indicating the presence of pollution. Igeo value for As in F2 was 0.74, which characterizes the soil in that area as unpolluted to moderately polluted (Table 3). Igeo values for Cr, Cu, Ni, Pb, and Zn in both farms (F1 and F2) and for As in F2 were negative, indicating absence of pollution in soils (Table 3).
Table 3. Assessment of geoaccumulation indices (Igeo) and potential ecological risk for pollution by heavy metals in samples of soil irrigated with Vieira River water in two farms (F1 and F2) (n = 8).
Igeo Sites Mean As Cr Cu Ni Pb Zn F1 Farm -0.10 -0.78 -1.24 -2.44 -1.56 -1.13 -1.21 F2 Farm 0.74 -0.31 -0.90 -0.92 -1.13 -0.48 -0.50 Mean 0.32 -0.54 -1.07 -1.68 -1.34 -0.80
Er Risk Sites RI As Cr Cu Ni Pb Zn level F1 Farm 13.98 2.21 3.85 1.25 1.31 6.97 29.56 Low F2 Farm 25.04 3.08 4.85 3.57 1.77 10.96 49.26 Low Mean 19.51 2.64 4.35 2.41 1.54 8.96 39.41 Low
RI – potential ecological risk index; and Er – ecological risk factor of certain heavy metal.
Mean Er of each analyzed heavy metal accounted for the following descending order: As > Zn > Cu > Cr > Ni > Pb. All analyzed metals (As, Cr, Cu, Ni, Pb, and Zn) featured low ecological risk in both farms (F1 and F2), according to the Er classification proposed by Hakanson (1980). Nevertheless, Er values were higher in F2, which indicates increased ecological risk in soils irrigated with water of Vieira River downstream of Montes Claros (Table 3). RI values were much lower than 110 in all sampling sites, indicating a low potential ecological risk. The As significantly contributed to the environmental RI, which can be attributed to the effect of anthropogenic activities. The As is used as preservative for leather and wood, additive for metal alloys, and in herbicides (Halli et al., 2014; Thuong et al., 2013). RI value was also higher at F2 (Table 3).
3.3. Heavy metal contamination in plants irrigated with water of Vieira River Contents of As and Zn in Brachiaria mutica plants in F2 were significantly higher (p < 0.05) than those found in Pennisetum purpureum plants in F1. On the other hand, Cu featured higher concentration (p < 0.01) in Pennisetum purpureum plants (F1). The mean content of heavy metals in plants of both farms (F1 and F2) accounted for the following descending order: Zn > Cu > Ni > As. Cr and Pb were not detected in forage grasses in both farms (F1 and F2) (Table 4).
Rev. Ambient. Água vol. 15 n. 2, e2440 - Taubaté 2020
8 Matheus Mendes Reis et al.
Table 4. Content of heavy metals (mg kg-1) in forage grasses irrigated with Vieira River water in two farms (F1 and F2) and transfer factor (TF) (n = 8).
Metals F1 Farm F2 Farm Normal Agronomic Widespread a b c Mean SD TF Mean SD TF intervals crop tolerance values of TF As 0.22** 0.04 0.70 0.26 0.02 0.48 1 - 1.7 - 0.01 - 0.1 (mg kg−¹) Cr 0.00 0.00 0.00 0.00 0.00 0.00 0.1 - 0.5 2 0.01 - 0.1 (mg kg−¹) Cu 7.63** 0.68 0.51 4.60 1.18 0.23 5 - 30 5 - 20 0.1 - 1 (mg kg−¹) Ni 0.50 0.35 0.10 1.05 1.11 0.07 0.1 - 5 1 - 10 0.1 - 1 (mg kg−¹) Pb 0.02 0.05 0.00 0.34 0.96 0.03 5 - 10 0.5 - 10 0.01 - 0.1 (mg kg−¹) Zn 50.77** 2.74 1.54 69.92 25.11 1.32 27 - 150 50 - 100 1 - 10 (mg kg−¹) SD – Standard deviation; TF – transfer factor; a – (Kabata-Pendias and Pendias, 2001); b - (Kabata- Pendias and Pendias, 2001; 1999; MacNicol and Beckett, 1985); c - (Kloke et al., 1984). * (p < 0.05) and ** (p < 0.01) indicate statistical difference (ANOVA; F-test) between mean values of metals in F1 and F2.
No metal exceeded the normal intervals (Kabata-Pendias and Pendias, 2001) or the agronomic crop tolerance values (Kabata-Pendias and Pendias, 1999; 2001; MacNicol and Beckett, 1985) (Table 4), including Cu and Ni, which featured concentrations in the water higher than the limits recommended by the Brazilian legislation for use of water in irrigation (CONAMA, 2005) (Table 1). The metal content in forage grasses depends not only on the content of metals in the soil, but also on the efficiency of metal transfer from the soil to the plants. This efficiency can be estimated by TF, which is one of the key indicators of human exposure to metals through the food chain (Cao et al., 2014), and is often used to study environmental pollution (Khan et al., 2013). TF values in both farms (F1 and F2) accounted for the following descending order: Zn > As > Cu > Ni. The highest TF values indicated that Zn and As were easily transferred from the soil to forage grasses when compared with other metals considered in this study. The As was the only metal accounting for TF higher than the widespread values (Kloke et al., 1984) (Table 4). The As mobility in the soil depends on pH, redox potential, and type and amount of adsorbents (oxides and hydroxides of Fe3+, Al3+, Mn3+, or Mn4+, humic substances, and clay minerals) present in the soil (Bissen and Frimmel, 2003; Oscarson et al., 1983). In addition, the amount of As adsorbed in the soil significantly decreased in the presence of organic matter (Bissen and Frimmel, 2003; Redman et al., 2002). Therefore, soil fertilization practices with animal manure at F1 farm, and use for irrigation of Vieira River water contaminated with sewage from Montes Claros at farm F2, contributed to the increase in the organic matter content in soils of these two farms (F1 and F2). This greater amount of organic matter in the soil can result in greater mobility of As (Bissen and Frimmel, 2003; Redman et al., 2002), which corroborates the fact that, in this study, such element featured TF values higher than the widespread values (Table 4). TF values of heavy metals were lower in F2 when compared with the values in F1 (Table 4), although there is higher content of heavy metal in the F2 soil (Table 2). This can be attributed to frequent flooding and drying of soils in F2 promoted by the flood irrigation system. Xie and Huang (1998) reported that water saturation and drying of soils, promoted by flooded rice irrigation, considerably increased the soil redox potential and, therefore, reduced As solubility and availability.
Rev. Ambient. Água vol. 15 n. 2, e2440 - Taubaté 2020
Heavy metals in soils and forage grasses … 9
4. CONCLUSION
Irrigation of agricultural lands with polluted water from Vieira River has increased the concentration of As and Ni in water; of As, Cr, Cu, Ni, Pb, and Zn in the soil; and of As and Zn in forage grasses. Pollution load index (PLI) and contamination factor (CF) indicated the existence of pollution and moderate contamination by As, Cr, and Zn in the soil of the farm downstream of the city of Montes Claros (F2), respectively. Values of the indicators of ecological risk (Er and RI) observed in the soil of both farms (F1 and F2) showed low ecological risk. However, these indicators were higher in the F2, which indicates increased ecological risk in soils irrigated with water of Vieira River downstream of Montes Claros. Surface flood irrigation may have contributed to the lower transfer factor (TF) of heavy metals found in the F2 farm; however, the use of this irrigation system in pasture areas is worrisome, because the direct contact of the animal with polluted water from Vieira River may facilitate the contamination of milk or meat of these animals by heavy metals or other inorganic or biological compounds. Furthermore, there must be greater awareness of contamination of forage grasses and soil by As, since this was the only metal that featured transfer factor (TF) higher than the widespread values found in literature and positive geoaccumulation index (Igeo), indicative of anthropogenic pollution.
5. ACKNOWLEDGMENTS
The authors thank Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for financial support; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for providing scholarships and financial support; and Espaço da Escrita – Pró-Reitoria de Pesquisa – UNICAMP – for the language services provided.
6. REFERENCES
APHA; AWWA; WEF. Standard Methods for the Examination of Water and Wastewater. 20. ed. Washington, 1998. 1134 p. BISSEN, M.; FRIMMEL, F. H. Arsenic – a Review. Part I: Occurrence, Toxicity, Speciation, Mobility. Acta hydrochimica et hydrobiologica, v. 31, n. 1, p. 9–18, 2003. https://doi.org/10.1002/aheh.200390025 CAO, S.; DUAN, X.; ZHAO, X.; MA, J.; DONG, T.; HUANG, N.; SUN, C.; HE, B.; WEI, F. Health risks from the exposure of children to As, Se, Pb and other heavy metals near the largest coking plant in China. Science of the Total Environment, v. 472, p. 1001–1009, 2014. https://doi.org/10.1016/j.scitotenv.2013.11.124 CHARY, N. S.; KAMALA, C. T.; RAJ, D. S. S. Assessing risk of heavy metals from consuming food grown on sewage irrigated soils and food chain transfer. Ecotoxicology and Environmental Safety, v. 69, n. 3, p. 513–524, 2008. https://doi.org/10.1016/j.ecoenv.2007.04.013 CHOPRA, A. K.; PATHAK, C. Accumulation of heavy metals in the vegetables grown in wastewater irrigated areas of Dehradun, India with reference to human health risk. Environmental Monitoring and Assessment, v. 187, n. 7, p. 445, 2015. https://doi.org/10.1007/s10661-015-4648-6
Rev. Ambient. Água vol. 15 n. 2, e2440 - Taubaté 2020
10 Matheus Mendes Reis et al.
CONAMA. Settlement n. 357 from March 17th 2005. It deals with the classification of water bodies and environmental guidelines for its classification, as well as establishes the conditions and standards for the discharge of effluents, and provides other measures. Diário Oficial [da] União: seção 1, Brasília, DF, n. 053, p. 58-63, 18 mar. 2005. CONAMA. Settlement n. 420 from December 30th 2009. It provides criteria and guiding values of soil quality for the presence of chemical substances and establishes guidelines for the environmental management of areas contaminated by these substances as a result of anthropic activities. Diário Oficial [da] União: seção 1, Brasília, DF, n. 249, p. 81-84, 30 dez. 2009. EU. Heavy Metals in Wastes, European Commission on Environment. Denmark, 2002. 86 p. EWERS, U. Standards, guidelines and legislative regulations concerning metals and their compounds. In: MERIAN, E. (Ed.). Metals and their Compounds in the Environment: Occurrence, Analysis and Biological Relevance. Weinheim: VCH, 1991. p. 458-468. GEBREKIDAN, A.; WELDEGEBRIEL, Y.; HADERA, A.; VAN DER BRUGGEN, B. Toxicological assessment of heavy metals accumulated in vegetables and fruits grown in Ginfel river near Sheba Tannery, Tigray, Northern Ethiopia. Ecotoxicology and Environmental Safety, v. 95, p. 171-178, 2013. https://doi.org/10.1016/j.ecoenv.2013.05.035 HAKANSON, L. An ecological risk index for aquatic pollution control. A sedimentological approach. Water Research, v. 14, n. 8, p. 975–1001, 1980. https://doi.org/10.1016/0043- 1354(80)90143-8 HALLI, M.; SARI, E.; KURT, M. A. Assessment of Arsenic and Heavy Metal Pollution in Surface Sediments of the Ergene River, Turkey. Polish Journal of Environmental Studies, v. 23, n. 5, p. 1581–1590, 2014. KABATA-PENDIAS, A.; PENDIAS, H. Biogeochemistry of Trace Elements. Warsaw: Wyd. Nauk PWN, 1999. KABATA-PENDIAS, A.; PENDIAS, H. Trace Elements in Soils and Plants. Boca Raton: CRC Press LLC, 2001. 331 p. KHAN, M. U.; MALIK, R. N.; MUHAMMAD, S. Human health risk from Heavy metal via food crops consumption with wastewater irrigation practices in Pakistan. Chemosphere, v. 93, n. 10, p. 2230–2238, 2013. https://doi.org/10.1016/j.chemosphere.2013.07.067 KLOKE, A.; SAUERBECK, D. R.; VETTER, H. The contamination of plants and soils with heavy metals and the transport of metals in terrestrial food chains. In: NRIAGU, J. O. (Ed.). Changing Metal Cycles and Human Health: Report of the Dahlem Workshop on Changing Metal Cycles and Human Health. Berlin, Germany: Springer, Berlin, 1984. p. 113–141. MACNICOL, R. D.; BECKETT, P. H. T. Critical tissue concentrations of potentially toxic elements. Plant and Soil, v. 85, n. 1, p. 107–129, 1985. https://doi.org/10.1007/BF02197805 MCCLUGGAGE, D. Heavy Metal Poisoning. Columbus: NCS Magazine. The Bird Hospital, 1991.
Rev. Ambient. Água vol. 15 n. 2, e2440 - Taubaté 2020
Heavy metals in soils and forage grasses … 11
OSCARSON, D. W.; HUANG, P. M.; HAMMER, U. T.; LIAW, W. K. Oxidation and Sorption of Arsenite By Manganese-Dioxide As Influenced By Surface-Coatings of Iron and Aluminum-Oxides and Calcium-Carbonate. Water Air And Soil Pollution, v. 20, n. 2, p. 233–244, 1983. https://doi.org/10.1007/BF00279633 R DEVELOPMENT CORE TEAM. R-plus® 3.4.2. Software. Zurich, 2017 REDMAN, A. D.; MACALADY, D. L.; AHMANN, D. Natural organic matter affects Arsenic speciation and sorption onto hematite. Environmental Science and Technology, v. 36, n. 13, p. 2889–2896, 2002. https://doi.org/10.1021/es0112801 SINGH, A.; SHARMA, R. K.; AGRAWAL, M.; MARSHALL, F. M. Health risk assessment of heavy metals via dietary intake of foodstuffs from the wastewater irrigated site of a dry tropical area of India. Food and Chemical Toxicology, v. 48, n. 2, p. 611–619, 2010. https://doi.org/10.1016/j.fct.2009.11.041 TAYLOR, S.; MCLENNAN, S. The geochemical evolution of the continental crust. Reviews of Geophysics, v. 33, n. 2, p. 241–265, 1995. https://doi.org/10.1029/95RG00262 THUONG, N. T.; YONEDA, M.; IKEGAMI, M.; TAKAKURA, M. Source discrimination of heavy metals in sediment and water of to Lich River in Hanoi City using multivariate statistical approaches. Environmental Monitoring and Assessment, v. 185, n. 10, p. 8065–8075, 2013. https://doi.org/10.1007/s10661-013-3155-x TUREKIAN, K. K.; WEDEPOHL, K. H. Distribution of the Elements in Some Major Units of the Earth’s Crust. Geological Society of America Bulletin, v. 72, n. 2, p. 175–192, 1961. https://doi.org/10.1130/0016-7606(1961)72[175:DOTEIS]2.0.CO;2 USEPA. Method 3051a - Microwave assisted acid digestion of sediments, sludges, soils, and oils. Washington: USEPA, 1998. USEPA. Guidelines for Water Reuse. Washington: USEPA, 2012. VAROL, M. Assessment of heavy metal contamination in sediments of the Tigris River (Turkey) using pollution indices and multivariate statistical techniques. Journal of Hazardous Materials, v. 195, p. 355-364, 2011. https://doi.org/10.1016/j.jhazmat.2011.08.051 WANG, M.; LIU, R.; LU, X.; ZHU, Z.; WANG, H.; JIANG, L.; LIU, J.; WU, Z. Heavy Metal Contamination and Ecological Risk Assessment of Swine Manure Irrigated Vegetable Soils in Jiangxi Province, China. Bulletin of Environmental Contamination and Toxicology, v. 100, n. 5, p. 634–640, 2018. https://doi.org/10.1007/s00128-018-2315-7 WHO. WHO guidelines for the safe use of wastewater, excreta and greywater: volume II. Geneva: World Health Organization, 2006. XIE, Z. M.; HUANG, C. Y. Control of arsenic toxicity in rice plants grown on an arsenic- polluted paddy soil. Communications in Soil Science and Plant Analysis, v. 29, n. 15– 16, p. 2471–2477, 1998. https://doi.org/10.1080/00103629809370125
Rev. Ambient. Água vol. 15 n. 2, e2440 - Taubaté 2020
Ambiente & Água - An Interdisciplinary Journal of Applied Science ISSN 1980-993X – doi:10.4136/1980-993X www.ambi-agua.net E-mail: [email protected]
Inadequate riparian zone use directly decreases water quality of a low-order urban stream in southern Brazil
ARTICLES doi:10.4136/ambi-agua.2451
Received: 13 Aug. 2019; Accepted: 06 Feb. 2020
Enzo Luigi Crisigiovanni1* ; Elynton Alves do Nascimento2 ; Rodrigo Felipe Bedim Godoy3 ; Paulo Costa de Oliveira-Filho2 ; Carlos Magno de Sousa Vidal2 ; Kelly Geronazzo Martins2
1Programa de Pós-Graduação em Ciências Florestais. Universidade Estadual do Centro-Oeste (UNICENTRO), Rua Professora Maria Roza Zanon de Almeida, S/N, CEP 84505-677, Irati, PR, Brazil. 2Departamento de Engenharia Ambiental. Universidade Estadual do Centro-Oeste (UNICENTRO), Rua Professora Maria Roza Zanon de Almeida, S/N, CEP 84505-677, Irati, PR, Brazil. E-mail: [email protected], [email protected], [email protected], [email protected] 3Departamento de Meio Ambiente. Universidade Estadual de Maringá (UEM), Avenida Ângelo Moreira da Fonseca, nº 1800, CEP: 87506-370, Umuarama, PR, Brazil. E-mail: [email protected] *Corresponding author. E-mail: [email protected] ABSTRACT Considering the current importance watercourses quality conservation, it is important to establish relationships between parameters that enable evaluation of the origins of changes in water quality, allowing actions to mitigate them. However, it is important to improve the association of different variables and to take sufficient samples. This study associates usual techniques and parameters to analyse the water quality of an urban river from Paraná State, Brazil. For this, we used biological indicators (aquatic macroinvertebrates), physical-chemical (temperature, turbidity, true colour, pH, DO and BOD5,20) indicators and microbiological (faecal and total coliforms) indicators. These indicators were related to land use and occupation classes obtained from high resolution QuickBird 2 images. For this association, the surroundings (450 meters buffer) of three distinct points of the river were considered: I. Near the spring; II. In the downtown city; and III. In a residential neighbourhood. Different values of physical, chemical and microbiological variables were detected along the river, showing evident relationships between them and with the use and occupation of the urban and peri-urban space in the characterization of surface waters. The association design was able to detect the landscape effect on water quality in a coherent way and that these connections were mainly related to suppression of the riparian forest present in the surroundings, further demonstrating the importance of this vegetation for the maintenance of watercourse quality.
Keywords: aquatic macroinvertebrates, physical-chemical parameters, water resources. O uso e ocupação inadequados da zona ciliar diminuem a qualidade da água de um rio urbano de pequena ordem no sul do Brasil RESUMO Visto a importância da conservação da qualidade dos cursos hídricos atualmente, torna-se indispensável estabelecer relações entre variáveis que permitam avaliar as origens de alterações
This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
2 Enzo Luigi Crisigiovanni et al. na qualidade das águas, permitindo a realização de ações que possam minimizá-las. Contudo, é importante buscar melhorias na associação das diferentes variáveis, com esforço amostral adequado. O presente associa técnicas e parâmetros comumente utilizados e de fácil acesso para analisar a qualidade da água de um rio urbano no estado do Paraná. Para isso, foram utilizados indicadores biológicos (macroinvertebrados aquáticos), físico-químicos (temperatura, turbidez, cor verdadeira, pH, OD e DBO5,20) e microbiológicos (coliformes fecais e totais). Esses indicadores foram relacionados com os tipos de uso e ocupação da terra obtidos a partir de imagens QuickBird2. Para essa associação foram considerados o entorno (450 metros de buffer) de três pontos distintos do rio: I. Próximo a nascente; II. No centro da cidade e III. Em um bairro residencial. Diferentes valores de variáveis físicas, químicas, microbiológicas e da comunidade de macroinvertebrados foram detectados ao longo do rio, demonstrando relações evidentes entre si e com o uso e ocupação do espaço urbano e peri-urbano na caracterização de águas superficiais. Concluímos que a associação utilizada conseguiu detectar o efeito da paisagem na qualidade da água de forma coerente e que estas relações estão principalmente atreladas a supressão da mata ciliar presente no entorno, demonstrando a importância desta vegetação para a manutenção da qualidade dos cursos hídricos.
Palavras-chave: macroinvertebrados aquáticos, parâmetros físico-químicos, recursos hídricos. 1. INTRODUCTION
Throughout history, watercourses have played an important role in supporting society, but the expansion of human settlements and urban areas has intensified the deterioration of water quality, as watercourses have become targets of indiscriminate disposal of effluents and alterations (Larson et al., 2019). In Brazil, Permanent Preservation Areas consist of marginal strips of legally protected watercourses, which may or may not present native vegetation. Moreover, their environmental function is to safeguard water resources, landscape, geology, soil and local biodiversity, besides offering sustenance and well-being to human populations (Brasil et al., 2009). Thus, if water quality is the result of a series of natural phenomena occurring in a watershed, it can reasonably be considered that the way man changes these natural systems, uses and occupies the land, has a direct impact on water quality (WHO, 2004; Silveira et al. 2016). Water quality is usually evaluated from the perspective of physical and chemical variables. However, these evaluations can be limited and lead to instantaneous diagnosis of the studied section. On the other hand, bioindicators, represented in watercourses mainly by aquatic macroinvertebrates, are organisms chosen for their sensitivity or tolerance to environmental changes. Given the dynamics of their respective life cycles, they represent scenarios in a broader spatial and temporal ways, including changes in land-use The municipality of Irati, located in the south-central region of Paraná state, Brazil, is strategically important from the standpoint of environmental conservation, since the area includes the watershed of the three main river basins of Paraná State: the Iguaçu, Ivaí and Tibagi River Basins (Maack, 2017; Mazza et al., 2005). The municipality has undergone diversification and expansion of economic activities over time, accelerating the anthropization and heterogenization of the landscape and generating pressures on water courses, especially on the Antas River, which has a large part of its course located within the urban area (Orreda, 2004). The Antas River is a low-order river and an important tributary of the Imbituvão River, from where the waters are collected for region supply, being part of Tibagi River Basin. However, the Antas River currently presents serious problems related to water quality and suppression of riparian forest, particularly showing irregular occupation of the banks and
Rev. Ambient. Água vol. 15 n. 2, e2451 - Taubaté 2020
Inadequate riparian zone use directly decreases water … 3 discharge of effluents (Andrade and Felchak, 2009; Haberland et al., 2012). The main objective of this study was to evaluate and associate physico-chemical and biological variables taking into account the influence of the land use and occupation. This work was designed to obtain information with little space-time effort, associating water quality indexes and land use, mainly related to urbanization. Furthermore, we stress the pioneering of this study for the central west region of Paraná state, contributing to the preservation of the Antas River.
2. METHODS AND MATERIAL
2.1. Characterization and location of study areas The present study was developed in Irati, Paraná, whose climate according to Köppen- Geiger climate classification is Cfb. The average temperature of 17.5°C, 1476 mm is the average annual rainfall. July is the driest month, with an average of 4 mm rainfall and October the rainiest with a mean of 175 mm (IAPAR, 2018). The city is located in the phyto ecological region of Mixed Ombrophilous Forest and the sections of the present study are concentrated specifically in the Alluvial Ombrophilous Forest typology, although the vegetation is in process of regeneration or non-existent. Three points in the urban perimeter of Irati were selected for sampling: Point 1: (25°30'1.50" S / 50°37'43.39" W) stretch with riverbed characterized by sandy-rocky bottom, 3 m wide, presenting remnants of native vegetation, as well as areas of forestry and recovery. Point 2: (25°28'13.76" S / 50°39'28.91" W) sandy / muddy watercourse segment, 5 m wide average, a region marked by absence of riparian vegetation and irregular occupation of the margin. Point 3: (25°27'43.00" S / 50°39'20.86" W) stretch with 4 m wide, on average, characterized by sandy bottom and predominantly with slab and partial presence of riparian forest. Based on the theory that rivers follow the principle of a continuum system (Larsen et al., 2019), collection points selection followed the choice criterion according to landscape composition change. 2.2. Land Use A QuickBird 2 high resolution spatial image was used, the image had the atmosphere corrected by dark-object subtraction algorithm, which minimizes shadow effects and possible detection errors in the sensor (Chavez Jr., 1988). In sequence, the radiance values of the image were converted to reflectance and the radiometric resolution was converted to 8 bits. The image was still orthorectified by the digital elevation model (DEM) and the multispectral - RGB (2.4 m) and panchromatic (0.61 m) bands, was merged to obtain the monochromatic spatial resolution. After the image pre-processing, it was clipped by buffers of 450 m radius, with the centre in the coordinates of the collection points. This radius size was determined to avoid overlapping between the sampled points (specifically Points 2 and 3, see Figure 1B) preventing spatial autocorrelation between the sampled water quality parameters (Frieden et al., 2014). Another important criterion for determining the radius is the landscape scale that influences macroinvertebrates community, since 500-meters distant environmental changes can jeopardize the aquatic community (Yirigui et al., 2019). In sequence, classes of land use were defined: I. Arboreal vegetation, represented by the Mixed Ombrophylous Forest or Araucaria Forest; II. Agriculture and field, represented by the cultivation of commercial species fields / herbaceous-shrub vegetation; III. Forests represented by field areas with occurrence of isolated trees; IV. Urban perimeter area represented by areas with low density of built-up area; and V. Urban Area represented by built up (developed) and / or paved areas (with high density of built up area). The interpretation work was performed by cognitive interpretation and manual vectoring, followed by association to the predefined classes. The validation of the classification was done by field verification. We assumed that by not using automatic or semi-automatic classification methods, accuracy measurements are
Rev. Ambient. Água vol. 15 n. 2, e2451 - Taubaté 2020
4 Enzo Luigi Crisigiovanni et al. redundant. After the interpretative work, the calculation of areas by class and their respective occupancy rates obtained; all this process was performed in SPRING 5.4.3 (Camara et al., 1996) a free and open source software developed by the National Institute for Space Research (Brazil). 2.3. Water quality variables, macroinvertebrates collection and identification Monitoring of water quality for both physicochemical and microbiological variables and for macroinvertebrates was carried out through eight monthly collections from April to November 2013 at the three points studied. The water samples were submitted to the following physicochemical analyzes: temperature, turbidity, pH, dissolved oxygen (DO), chemical oxygen demand (BOD5,20); and microbiological tests: FC - Faecal coliforms (Escherichia coli) and TC – Total coliforms. The macroinvertebrates were sampled using "D" net with 300μm mesh. Collected material was taken to laboratory for screening and individuals were identified at taxonomic level of family (subclass for Annelida) for application of the biological indexes. 2.4. Data analysis The physical-chemical and microbiological variables were analyzed using the water quality index (WQICETESB), which consists of nine variables, including six of the seven variables sampled, for which we resized the weights of each variable: Temperature (Wi = 0.14 ); Turbidity (Wi = 0.12); pH (Wi = 0.16); DO (Wi = 0.23); BOD5,20 (Wi = 0.14) and FC (Wi = 0.21). These variables were also compared between the points by analysis of variance (one-way ANOVA), where the points were the factor (with 3 levels), and the dependent variables were water quality parameters. The four collections were replicates. The assumptions of Gaussian distribution and homogeneity of variance were checked using Shapiro-Wilks and Bartlett tests, respectively. When the data did not match the premises, they were transformed by means of square root. The results for macroinvertebrates were estimated by calculating 5 indexes: I. Relative percentage of Chironomidae (% Chironomidae); II. Relative percentage of Ephemeroptera, Plecoptera and Trichoptera (% EPT); III. BMWP'- Biological Monitoring Working Party, modified by IAP (2003); IV. ASPT - Average Score Per Taxon; and V. RAPHD - Rapid Assessment Protocol for Habitat Diversity (Callisto et al., 2002). To compare if there were differences in macroinvertebrate community as a function of the individual’s abundance, a Permutational Multivariate Analysis of Variance (PERMANOVA) test (Anderson, 2008) was applied, with 999 permutations of residues in the complete model, and Bray-Curtis distance (Legendre and Legendre, 1988). In order to compare this difference between the communities and association of possible patterns with physical chemical variables, we applied a CCA test (Canonical Correspondence Analysis), which was adjusted by the stepwise method, which incorporated only physical-chemical variables that presented a significance greater than 5% to the model (Ter Braak, 1986). Finally, Pearson correlations were calculated between the indexes presented above with the percentages obtained in the land-use and occupation classification, using the "vegan" package (Oksanen et al., 2017) of the R-project 3.3.3. 3. RESULTS AND DISCUSSION Image classification revealed a contrast between the percentages of the classes for each point. Point 1 presented 0.22 km² (34.4%) of forest and 0.18 km² (28.1%) of peri-urban area, respectively; Point 2 presented 0.56 km² (87.50%) of urban area; and Point 3, 0.28 km² (43.8%) of periurban area and 0.24 km² (37.5%) of woods, respectively (Figure 1C). The mean values of physicochemical and microbiological variables are presented in Table 1. Among the variables of water quality that presented significant variation, are FC and TC (Figure 2). Statistical differences were found between the area of river spring (Point 1 (a)) and the urban and peri-urban region (Points 2 and 3 (b)), making clear the negative influence of this area on the quality of river waters.
Rev. Ambient. Água vol. 15 n. 2, e2451 - Taubaté 2020
Inadequate riparian zone use directly decreases water … 5
Figure 1. (A) geographical location of Irati and its urban perimeter in Paraná state, Brazil (B) Location map of Antas River and its route within Irati urban perimeter, showing the collection points with 450 m classified buffers. (C) On the right are the buffers and their classes, according to the legend in Figure 1B, and on the left a pie chart with the percentages of area for each buffer.
Table 1. Mean and standard deviation of physicochemical and microbiological variables of the eight collections. Point 1 Point 2 Point 3 MAV Temp. (ºC) 16.6 ± 4.0 17.0 ± 4.0 17.4 ± 4.2 - Turbidity (NTU) 27.7 ± 15.2 41.9* ± 38.5 37.5 ± 34.8 40 pH 6.9 ± 1.4 7.2 ± 0.2 7.2 ± 0.3 6 - 9 TrueColour (uH) 90.5 ± 48.8 95.6 ± 59.2 92.6 ± 69.3 - DO (mgL-1) 8.3 ± 0.5 8.0 ± 0.6 8.3 ± 0.7 < 6 -1 BOD5,20 (mgL ) 1.2 ± 0.4 4.48* ± 2.8 2.5 ± 1.2 3 TC ** (CFU) 9650* ± 6676 44775* ± 24180 43825* ± 25954 200 FC ** (CFU) 700* ± 967 12162* ± 9894 13762* ± 8596 0 Legend: MAV - Maximum Allowed Value, by CONAMA Resolution No. 357/2005 (CONAMA, 2005) for Class I waters; * Values above those allowed; ** Significant difference between points for 5% probability.
Rev. Ambient. Água vol. 15 n. 2, e2451 - Taubaté 2020
6 Enzo Luigi Crisigiovanni et al.
Figure 2. Boxplots of microbiological variables of water quality from three points of the Antas River (Irati, Paraná). The means followed by the same letter (b) do not differ statistically by the Tukey test at 5% significance.
In Brazil, studies commonly reveal high presence of E. coli in freshwaters, mainly in sites with agriculture and urbanization predominance (Mello et al., 2018). Handam et al. (2018), for example, found values 170.6 and 192.3 times greater than allowed by the legislation for FC and TC, respectively, in Rio de Janeiro. E. coli is a variable that represents a real faecal contamination of water, and Figure 2 reflects the condition of urbanization that occurs in Points 2 and 3. Considering the large occupation area around Point 2 (88% of urban area), it is possible to relate the occurrence of these pathogenic organisms with discharge of sanitary effluents, corroborating the studies of Haberland et al. (2012), who verified high values of E. coli in points with the highest human occupation in the Antas River. In spite of this, it is important to emphasize that even though this difference exists, the values of TC and FC in the three points presented values higher than those allowed by Brazilian legislation (Table 1); therefore, areas with a higher percentage of agricultural area do not represent certainty of values according legislation, as also found by Pessoa et al. (2018). None of the other variables evaluated here presented statistically different values between the points. However, for Point 2, only BOD5,20 and Turbidity exceeded the permitted values determined by the current government legislation and regulations (5 mg/L and 40 NTU, respectively) (Table 1), unlike Andrade and Felchak (2009) and Haberland et al. (2012), who verified values higher than allowed by legislation in all points sampled in the same river studied here. This result confirms field-work observations, that indicated the possibility of contribution of domestic effluents upstream of collection sites and corroborates the results of Pessoa et al. (2018), which found higher BOD5,20 values at points with higher indexes of human occupation. Regarding the macroinvertebrate community, PERMANOVA showed significant difference between sampling points (F2,23 = 2.26, p = 0.026) and the correspondence analysis can represent this difference through the formation of groups referring to each collection and the largest association of tolerant taxa with BOD5,20 and TC, indicative of pollution (Figure 3). The CCA adds information that the water quality variables significantly influence the macroinvertebrate community. Specifically, BOD and TC are responsible for the differences in water quality and, consequently, in the distinctions of macroinvertebrate assemblages between the points studied. The first axis of CCA (CCA 1 = 0.79) is highly correlated with BOD and all macroinvertebrate samples from Point 1, since the arrow corresponding to BOD is opposite for this group, it can be concluded that the BOD values are smaller in Point 1 and larger in some samples from Points 2 and 3. TC is negatively correlated with samples from Point 1 and positively correlated with samples from Points 2 and 3.
Rev. Ambient. Água vol. 15 n. 2, e2451 - Taubaté 2020
Inadequate riparian zone use directly decreases water … 7
Figure 3. CCA associating the community of macroinvertebrates (represented by P1, P2 and P3 and collections, C1 to C8), with physical chemical and microbiological variables (BOD5,20 and TC, p < 0.05).
It is also observed that Point 1 was grouped with greater cohesion and presented smaller variation in its values, since Points 2 and 3 were stored in a larger group (with high variation), the same pattern found for microbiological variables when submitted to ANOVA (Figure 3). This differentiation between the points demonstrates direct response of these organisms to environmental quality of the water body (Strohschoen et al., 2009; Silva et al., 2015; Chagas, et al., 2017). In relation to the quality biotic indexes (Table 2), % Chironomidae, % EPT and BMWP' and ASPT indexes, it is observed that better values were found in Point 3 followed by Point 1, and the worst values were associated to Point 2. The RAPHD and WQICETESB indicated higher scores for Point 1, followed by Point 3 and lastly Point 2. However, WQICETESB establishes the same category for the three points (Table 2). The configuration of these indexes values are probably due to urban occupation in its surroundings, since Point 1 is near a river spring, Point 2 is located in the urban center of the city and Point 3 is also in an urban setting, but presenting lower population density and riparian forest, as observed in Figure 1C. The RAPHD showed significant correlation with land use, areas of forest and arboreal vegetation (rPearson = (+) 0.99, p = 0.046). The difference of the RAPHD, as well as the WQICETESB in relation to the other indexes should be emphasized, since they take into account the structural- and physicochemical variables of the environment, respectively, factors that can explain this association between vegetation and the index (Callisto et al., 2002). In this way, BOD5,20 was also correlated with RAPHD (rPearson = (-) 0.99, p = 0.05), relating domestic sewage contamination with urbanization densities (Venancio et al., 2010).
Rev. Ambient. Água vol. 15 n. 2, e2451 - Taubaté 2020
8 Enzo Luigi Crisigiovanni et al.
Table 2. Biotic and environmental quality indexes calculated for three stretches of the Antas River (Irati, Paraná, Brazil). Point 1 Point 2 Point 3 %Chironomidae 70. 81 62.22 48.99 %EPT 8.93 3.33 31.86 BMWP’ 74A 58B 97A ASPT 4.35D 3.86E 5.10C RAPHD 91F 28G 71H G G G WQICETESB 66 54 56 Legend: A - Doubtful; B - Polluted; C - Questionable quality; D - Moderate pollution; E - Severe pollution; F - Natural; G - Impacted; H - Altered; I – Good.
The WQICETESB was not significant, however, when correlated directly with the variables that compose it; we found a significant relation of agricultural culture with pH and TC (rPearson = (+) 0.99; p < 0.01). This association demonstrates coherence, considering the loss of soil nutrients and organisms (Silveira et al., 2016), as observed in Point 1, the only site presenting such a category, with values of 15% (Figure 1C). All the other variables showed trends to the expected (that riparian’s forest reduction decrease the water quality), but did not show significance for this level of probability. In general, urban rivers have a lower density (or even absence) of sensitive organisms when compared to preserved areas; but in rural waterways there is an increase in the density of these organisms, reinforcing their low tolerance for anthropic changes (Ometto et al., 2004; Hepp et al., 2010). The change in land use causes homogenization of the functional structure of the aquatic insect community (Castro et al., 2018). However, the data of Point 3 resemble features of natural areas; this point was placed in an area where the river already passed through the downtown city, riparian forest are present again and a resilient process can be found. This demonstrates that restoration of riparian forest can be a determining factor in water quality. Riparian zones over 15m width are more suitable for maintenance of macroinvertebrate community composition and trophic structure, but even a reduced riparian-zone width can maintain minimal conditions to support these communities (Moraes et al., 2014). Moreover, despite the higher importance of forest conservation at watershed scale, restoration of riparian zone is a basic feature to improve the water quality (Mello et al., 2018). Considering this forest as a linking element that acts like an environmental filter between terrestrial and aquatic ecosystems, it is necessary to re-evaluate the current practices of land use and occupation in their environment (Gregory et al., 1991; Roy et al., 2003; Larson et al., 2019).
4. CONCLUSION
The Antas River and its tributaries, from their springs to their mouths, presents several types of land use, such as agricultural, industrial and even domestic sewage treatment, activities that have high environmental impacts. The present work pointed out that inadequate land use and occupancy reflects negatively impacts water quality of the ecosystem. This work also showed the effectiveness of the use of orbital images and geoprocessing techniques using joint physical-chemical and biological parameters for monitoring watercourses. These processes could complement the current water quality monitoring and facilitate collaborative efforts to confirm presumable pollution sources, being punctual or diffused. We can conclude that water quality variables and landscape use association was effective, so a spatial landscape vision can improve the surface characterization for riparian land planning and use. More studies like the one presented here, studying other rivers and/or basins in urban
Rev. Ambient. Água vol. 15 n. 2, e2451 - Taubaté 2020
Inadequate riparian zone use directly decreases water … 9 regions, or the contrast with preserved areas, thus verifying the effect of riparian forest in the recovery of water quality, will contribute to a better understanding of the effects of urbanization in water courses. In addition, this type of study can be applied to evaluate the effects of restoration/mitigation actions on rivers and/or habitats, giving support to conservation of these urban ecosystems. 5. ACKNOWLEDGEMENTS
The authors would like to thank CNPq (National Council for Scientific and Technological Development of Brazil), Araucária Foundation for the research grants and the Municipality of Irati for the satellite images provided. 6. REFERENCES ANDERSON, M. J. A. New method for non-parametric multivariate analysis of variance. Austral Ecology, v. 26, p. 32–46, 2008. https://dx.doi.org/10.1111/j.1442- 9993.2001.01070.pp.x ANDRADE, A. P.; FELCHAK, I. M. A poluição urbana e o impacto na qualidade da água do rio das Antas – Irati-PR. Geoambiente, v. 12, p. 108-132, 2009. https://doi.org/10.5216/rev.%20geoambie.v0i12.25985 BRASIL, K. D. C. M. T.; CAMARGO III, B. V. Macroinvertebrados bentônicos como indicadores do impacto ambiental promovido pelos efluentes de áreas orizícolas e pelos de origem urbana/industrial. Ciência Rural, v. 39, n. 7, p. 2087-2092, 2009. https://dx.doi.org/10.1590/S0103-84782009005000161 CALLISTO, M.; FERREIRA, W. R.; MORENO, P.; GOULART, M.; PETRUCIO, M. Aplicação de um protocolo de avaliação rápida da diversidade de hábitats em atividades de ensino e pesquisa (MG-RJ). Acta Limnologica Brasiliensia, v. 14, n. 1, p. 91-96, 2002. http://jbb.ibict.br//handle/1/708 CAMARA, G.; SOUZA, R. C. M.; FREITAS, U. M.; GARRIDO, J. SPRING: Integrating remote sensing and GIS by object-oriented data modeling. Computers & Graphics, 1996, v. 20, n. 3, p. 395-403, 1996. CASTRO, D. M. P.; DOLÉDEC, S.; CALLISTO, M. Land cover disturbance homogenizes aquatic insect functional structure in neotropical savanna streams. Ecological Indicators, v. 84, p. 573-582, 2018. https://doi.org/10.1016/j.ecolind.2017.09.030 CHAGAS F. B.; RUTKOSKI, C. F.; BIENIEK, G. B.; VARGAS, G. D. L. P.; HARTMANN, P. L.; HARTMANN, M. T. Utilização da estrutura de comunidades de macroinvertebrados bentônicos como indicador de qualidade da água em rios no sul do Brasil Revista Ambiente & Água, v. 12, n. 3, 2017. https://dx.doi.org/10.4136/ambi- agua.2015 CHAVEZ Jr., P. S. An improved dark-object subtraction technique for atmospheric scattering correction of multispectral data. Remote Sensing of Environment, v. 24, n. 3, p. 459– 479, 1988. https://doi.org/10.1016/0034-4257(88)90019-3 CONAMA (Brasil). Resolução nº 357 de 17 de março de 2005. Dispõe sobre a classificação dos corpos de água e diretrizes ambientais para o seu enquadramento, bem como estabelece as condições e padrões de lançamento de efluentes, e dá outras providências. Diário Oficial da União: seção 1, Brasília, DF, n. 053, p. 58-63, 18 mar. 2005.
Rev. Ambient. Água vol. 15 n. 2, e2451 - Taubaté 2020
10 Enzo Luigi Crisigiovanni et al.
FRIEDEN, J. C.; PETERSON, E. E.; WEBB, J. A.; NEGUS, P. M. Environmental Modelling & Software Improving the predictive power of spatial statistical models of stream macroinvertebrates using weighted autocovariance functions. Environmental Modelling and Software, v. 60, p. 320–330, 2014. http://dx.doi.org/10.1016/j.envsoft.2014.06.019 GREGORY, S. V.; SWANSON, F. J.; MCKEE, W. A.; CUMMINS, K. W. An ecosystem perspective of riparian zones. Bioscience, v. 41, p. 540–551, 1991. https://dx.doi.org/10.2307/1311607 HABERLAND, N. T.; SILVA, F. C. B.; OLIVEIRA FILHO, P. C.; VIDAL, C. M. S.; CAVALLIN, G. S. Análise da influência antrópica na qualidade da água do trecho urbano do Rio das Antas na cidade de Irati, Paraná. Revista Tecnológica, v. 21, p. 53-67, 2012. https://doi.org/10.4025/revtecnol.v21i1.15978 HANDAM, N. B.; SANTOS, J. A. A.; MORAES NETO, A. H. A.; DUARTE, A. N.; ALVES, E. B. S.; SALLES, M. J.; MARTINS A. S. Sanitary quality of the rivers in the Communities of Manguinhos´ Territory. Revista Ambiente & Água, v. 13, n. 1, 2018. https://dx.doi.org/10.4136/ambi-agua.2125 HEPP, L. U.; MILESI, S. V.; BIASI, C.; RESTELLO, R. M. Effects of agricultural and urban impacts on macroinvertebrates assemblages in streams (Rio Grande do Sul, Brazil). Zoologia, v. 27, n. 1, p. 106–113, 2010. http://dx.doi.org/10.1590/S1984- 46702010000100016 IAPAR. Climate charts from Paraná. 2018. Available at: http://www.iapar.br/modules/conteudo/conteudo.php?conteudo=677. Access: March 2018. IAP. Evaluation of Water Quality Through Benthonic Macroinvertebrates - BMWP Index. 2013. Available at: http://www.meioambiente.pr.gov.br/modules/conteudo/conteudo.php?conteudo=91. Access: March 2018. LARSEN, S.; BRUNO, M. C.; VAUGHAN, I. P.; ZOLEZZI, G. Testing the River Continuum Concept with geostatistical stream-network models. Ecological Complexity, v. 39, p. 100773, 2019. https://doi.org/10.1016/j.ecocom.2019.100773 LARSON, D. M.; DODDS, W. K.; VEACH, A. M. Removal of woody riparian vegetation substantially altered a stream ecosystem in an otherwise undisturbed grassland watershed. Ecosystems, v. 22, p. 64-76, 2019. https://dx.doi.org/10.1007/s10021-018-0252-2 LEGENDRE, P.; LEGENDRE, L. Numerical Ecology, v. 24, p. 870, 1988. https://dx.doi.org/10.1017/CBO9781107415324.004 MAACK, R. Geografia Física do estado do Paraná. 4. ed. Ponta Grossa: UEPG, 2017. p.140- 257. MAZZA, C. A. da S. Caracterização Ambiental dos Componentes Estruturais da Paisagem do Município de Irati, Paraná. Colombo: Embrapa Florestas, 2005. p. 45. MELLO, K.; VALENTE, R. A.; RANDHIR, T. O.; SANTOS, A. C. A.; VETTORAZZI, C. A. Effects of land use and land cover on water quality of low-order streams in Southeastern Brazil: Watershed versus riparian zone. Catena, v. 167, p. 130-138, 2018. https://doi.org/10.1016/j.catena.2018.04.027
Rev. Ambient. Água vol. 15 n. 2, e2451 - Taubaté 2020
Inadequate riparian zone use directly decreases water … 11
MORAES, A. B.; WILHELM, A. E.; BOELTER, T.; STENERT, C.; SCHULZ, U. H.; MALTCHIK, L. Reduced riparian zone width compromises aquatic macroinvertebrate communities in streams of southern Brazil. Environmental Monitoring and Assessment, v. 186, p. 7063-7074, 2014. https://doi.org/10.1007/s10661-014-3911-6 OMETTO, J. P.; GESSNER, A.; MARTINELLI, L. A.; BERNARDES, M. C. Macroinvertebrate community as indicator of land-use changes in tropical watersheds, southern Brazil. Ecohydrology & Hydrobiology, v. 4, n. 1, p. 37-49, 2004. OKSANEN, J.; BLANCHET, F. G.; FRIENDLY, M.; KINDT, R.; LEGENDRE, P.; MCGLINN, D.; MINCHIN, P. R.; O’HARA, R. B.; SIMPSON, G. L.; SOLYMOS, P.; STEVENS, M. H. H.; SZOECS, E.; WAGNER, H. Vegan: Community Ecology Package. R package version 2.4-3. 2017. Available at: https://CRAN.R- project.org/package=vegan. Access: March 2018. ORREDA, J. M. Educação em Irati: 1901 – 2001, Cem anos de história. Irati: O Debate, 2004. PESSOA, J. O.; ORRICO, S. R. M.; LORDELO, M. S. Qualidade da água de rios em cidades do Estado da Bahia. Engenharia Sanitária e Ambiental, v. 23, n. 4, p. 687-696, 2018. https://dx.doi.org/10.1590/s1413-41522018166513 ROY, A. H.; ROSEMOND, A. D.; PAUL, M. J.; LEIGH, D. S.; WALLACE, J. B. Stream macroinvertebrate response to catchment urbanisation (Georgia, U.S.A.). Freshwater Biology, v. 48, p. 329-346, 2003. https://dx.doi.org/10.1046/j.1365-2427.2003.00979.x SILVEIRA, G. A.; SARAN, L. M.; de MELO, W. J.; ALVES, L. M. C. Farming and soil urban occupation in the water quality of Jaboticabal and Cerradinho streams. Ciência e Agrotecnologia, v. 40, n. 6, p. 633-646, 2016. http://dx.doi.org/10.1590/1413- 70542016406048415 SILVA, J. C. de A.; PORTO, M. F. do A.; BRANDIMARTE, A. L.; MARTINS, J. R. S. Utilização de índices físicos, químicos e biológicos para avaliação da qualidade de corpos d’água em processo de recuperação – Córrego Ibiraporã, SP. RBRH – Revista Brasileira de Recursos Hídricos, v. 20, n. 4, p. 959–969, 2015. https://dx.doi.org/10.21168/rbrh.v20n4.p959-969 STROHSCHOEN, A. A. G.; PÉRICO, E.; DE LIMA, D. F. B.; REMPEL, C. Preliminary study of the quality of the water of Forqueta and Forquetinha rivers, RS state. Brazilian Journal of Biosciences, v. 7, n. 4, p. 372-375, 2009. TER BRAAK, C. J. F. Canonical correspondence analysis: a new eigenvector technique for multivariate direct gradient analysis. Ecology, v. 67, n. 6, p. 1167-79, 1986. https://dx.doi.org/10.2307/1938672 VENANCIO, D. L.; OLIVEIRA-FILHO, P. C.; DISPERATI, A. A. Uso do geoprocessamento em estudo ambiental na Bacia do Rio das Antas, Irati (Paraná). Ambiência, v. 10, n. 6, p. 135-146, 2010. WHO. Guidelines for drinking water quality. Genebra, 2004, 516 p. YIRIGUI, Y.; LEE, S. W.; NEJADHASHEMI, A. P.; HERMAN, M. R.; LEE, J. W. Relationships between riparian forest fragmentation and biological indicators of streams. Sustainability (Switzerland), v. 11, n. 10, p. 1–24, 2019. https://doi.org/10.3390/su11102870
Rev. Ambient. Água vol. 15 n. 2, e2451 - Taubaté 2020
Ambiente & Água - An Interdisciplinary Journal of Applied Science ISSN 1980-993X – doi:10.4136/1980-993X www.ambi-agua.net E-mail: [email protected]
Proposal of optimal operation strategy applied to water distribution network with statistical approach ARTICLES doi:10.4136/ambi-agua.2455
Received: 19 Aug. 2019; Accepted: 06 Feb. 2020
Alex Takeo Yasumura Lima Silva1 ; Fernando das Graças Braga da Silva1* ; André Carlos da Silva1 ; José Antonio Tosta dos Reis2 ; Claudio Lindemberg de Freitas1 ; Victor Eduardo de Mello Valério3
1Instituto de Recursos Naturais. Universidade Federal de Itajubá (UNIFEI), Avenida BPS, n° 1303, CEP: 37500-903, Itajubá, MG, Brazil. E-mail: [email protected], [email protected], [email protected] 2Departamento de Engenharia Ambiental. Universidade Federal do Espírito Santo (UFES), Avenida Fernando Ferrari, n° 514, CEP: 29075-910, Vitória, ES, Brazil. E-mail: [email protected] 3Instituto de Engenharia de Produção e Gestão. Universidade Federal de Itajubá (UNIFEI), Avenida BPS, n° 1303, CEP: 37500-903, Itajubá, MG, Brazil. E-mail: [email protected] *Corresponding author. E-mail: [email protected] ABSTRACT Inefficiency of sanitation companies’ operation procedures threatens the population’s future supplies. Thus, it is essential to increase water and energy efficiency in order to meet future demand. Optimization techniques are important tools for the analysis of complex problems, as in distribution networks for supply. Currently, genetic algorithms are recognized by their application in literature. In this regard, an optimization model of water distribution network is proposed, using genetic algorithms. The difference in this research is a methodology based on in-depth analysis of results, using statistics and the design of experimental tools and software. The proposed technique was applied to a theoretical network developed for the study. Preliminary simulations were accomplished using EPANET, representing the main causes of water and energy inefficiency in Brazilian sanitation companies. Some parameters were changed in applying this model, such as reservoir level, pipe diameter, pumping pressures, and valve-closing percentage. These values were established by the design of experimental techniques. As output, we obtained the equation of response surface, optimized, which resulted in values of established hydraulic parameters. From these data, the obtained parameters in computational optimization algorithms were applied, resulting in losses of 26.61%, improvement of 16.19 p.p. with regard to the network without optimization, establishing an operational strategy involving three pumps and a pressure-reducing valve. We conclude that the association of optimization and the planning of experimental techniques constitutes an encouraging method to deal with the complexity of water-distribution network optimization.
Keywords: computational modeling, design of experiments, water losses, water resources. Proposição de estratégia operacional ótima aplicada a rede de distribuição de água com abordagem estatistica RESUMO A ineficiência dos procedimentos operacionais das companhias de saneamento ameaça o
This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
2 Alex Takeo Yasumura Lima Silva et al. abastecimento futuro da população. Assim, o aumento da eficiência hidroenergética mostra-se essencial para atender a demanda. As técnicas de otimização são ferramentas importantes na análise de problema complexos, que é caso das redes de distribuição de água para abastecimento, destacando-se os algoritmos genéticos, consagrados pela literatura. Neste sentido propõe-se aqui um modelo de otimização de operação de rede de distribuição de água utilizando algoritmos genéticos. O diferencial da pesquisa e metodologia baseada na análise dos resultados com o uso de ferramentas de estatística e planejamento de experimentos. A técnica foi aplicada a uma rede teórica desenvolvida para o estudo. Simulações preliminares foram feitas com o uso do Epanet representando as principais causas da ineficiência hidroenergética nas companhias de saneamento brasileiras. Para a aplicação do modelo foram alterados parâmetros tais como: níveis reservatórios, diâmetro das tubulações, pressões de bombeamento e fechamento de válvulas cujos valores foram estabelecidos através de técnicas de planejamento de experimentos. Obteve-se a equação da superfície de resposta, otimizada, que resultou nos valores dos parâmetros hidráulicos estabelecidos. Então, aplicou-se os então os parâmetros obtidos no algoritmo de otimização computacional, resultando em perdas de 26,61%, melhoria de 16,19 p.p. em relação a rede sem otimização, estabelecendo uma estratégia operacional envolvendo três bombas e uma válvula redutora de pressão. Conclui-se que a associação de técnicas de otimização a planejamento de experimentos constitui uma promissora técnica para tratar da complexidade de otimização de rede de distribuição de água.
Palavras-chave: modelagem computacional, perdas de água, planejamento de experimentos, recursos hídricos.
1. INTRODUCTION
Increasing population as well as rising demand have been putting water resources under increasing pressure, which, along with climate changes, are resulting in water scarcity, a challenging problem which will become more frequent and severe in the future. Thus, global distribution of water resources, essential for life, the economy and the social structure of urban environments, have been affected, putting the population’s water safety at risk. (Chini and Stillwell, 2018; Liu et al., 2019). Water leakage can reach 45 billion cubic meters worldwide; reduction by half would be enough to ensure the supply of 200 million people with no need of investments in funding and exploitation of springs, reducing part of sanitation companies’ financial loss, which is about US$ 14 billion per year. This problem would limit investment capacity in system improvement and expansion and also implicitly reduce power consumption required for water treatment and distribution. (Coelho and Andrade-Campos, 2014; Kanakoudis and Muhammetoglu, 2014; Mutikanga et al., 2013). Losses can be divided into apparent losses, caused by commercial issues such as collection errors, faulty hydrometers, and non-authorized consumption, and real losses, caused by leakages in joints, connections or holes (Sanz et al., 2016). Besides financial, power and environmental losses arising from real losses, there is also the sanitary risk due to the possibility of contaminant infiltrations in piping, requiring operational strategies for mitigation (Candelieri et al., 2013). Thus, a strategy for reduction of losses due to leakages is the management of pressures in network; that is, the adequacy of operational procedures to ensure adequate values of pressures in networks, assuring suitable conditions for water supply. (Fontana et al., 2012; Han and Liu, 2017). For establishing an optimal operational strategy, optimization techniques are employed. These are considered an essential part of water-resource planning and management, especially in the case of water distribution networks in which area studies have been developed. Computational simulation is used in networks to allow application of optimization techniques
Rev. Ambient. Água vol. 15 n. 2, e2455 - Taubaté 2020
Proposal of optimal operation strategy applied to … 3 to ensure an adequate and sustainable water supply with adequate pressures. Pressure management in a network is a great concern for sanitation companies, since excessive pressures are the main cause of real losses. Meanwhile, very low pressures do not allow adequate water supply for the population, leading in many cases to lack of water at particular points of the network (Khatavkar and Mays, 2017; Oikonomou and Parvania, 2018; Tanyimboh and Seyoum, 2017; Vakilifard et al., 2018). When operating a network, optimization aims to reduce operational costs of collection and distribution system, such as pump activation, treatment and distribution to meet water demand within the system (Soler et al., 2015). The technique usually used to evaluate water-resource problems is genetic algorithms, based on the evolution principle, which states that only the more adapted individual will survive and generate descendants. This technique is used in several problems related to water distribution networks, from operation to design, always aiming for a better meeting of needs with the lowest possible power consumption. (Bi et al., 2015; Creaco and Pezzinga, 2015) Establishing scenarios to be simulated, as well as obtaining optimal levels of network operation, required the use of the Design of Experiments technique (DOE). This method uses data planning and gathering in a systematized manner to process characteristics modeled according to experimental data, also allowing the use of Methodology of Surface Response (MSR), which makes possible the representation of responses of interest – in this case, losses in the network – by the use of a polynomial of second order, which can be optimized to reach factors leading to such a result, and is used in several areas (Barimani et al., 2018; Gomes, 2013; Yu et al., 2018).
2. CASE STUDY
The work phases are defined in the form of a flowchart, as shown in Figure 1.
Figure 1. Flow chart of work phases.
For developing optimization programs, it was necessary to prepare a theoretical network capable of adjusting to the proposal of this paper, intending to include minimum components to allow the adequate analysis of its operation. The objective is to avoid an expensive computational implementation, and at the same time to look for a proximity with irregular relief regions, which is usually complicated when regarding water distribution. The theoretical network developed for the paper was a branched network with irregular topography, aiming for simplicity of implementation, able to meet the mandatory analysis requirements, created in EPANET software and displayed with elevations and demands of nodes in Figure 2.
Rev. Ambient. Água vol. 15 n. 2, e2455 - Taubaté 2020
4 Alex Takeo Yasumura Lima Silva et al.
Figure 2. Theoretical water-distribution network.
Data employed for network simulation were based on commercial diameters found in Porto (2006) and in rugosities adopted by Silva (2003), as shown in Table 1.
Table 1. Data of network branches. Pipes Node Rugosity (mm) Diameter (m) Length (m) 1 1-2 0.25 0.400 1500 2 2-3 0.25 0.300 950 3 2-4 0.25 0.300 900 4 2-5 0.25 0.400 1750 5 5-6 0.25 0.350 1100 6 5-7 0.25 0.250 800 7 5-8 0.25 0.400 1000 8 8-9 0.25 0.250 750 9 9-10 0.25 0.150 500
3. METHODOLOGY
Once the network in EPANET was in place and the first set of data was obtained, the optimization program was written in the FORTRAN 90 language, as well as the modulus responsible for network optimization by using genetic algorithms and hydraulic calculations. The calibration algorithm of Silva (2003) was used for the calibration of the theoretical network throughout the data obtained by EPANET. The optimization program has a genetic algorithm coupled with a hydraulic calculus module for network optimization, divided in subroutines. First, data passes through a rugosity optimization subroutine, which generates slight changes in rugosity to simulate the aging of pipe materials. Afterwards, the data goes through crossover and then passes to a mutation subroutine, which has a 10% mutation probability. After this, the data goes through the reservoir-level optimization subroutine, which uses one of the reservoir heads pre-established in Table 2 and goes to the hydraulic calculation module, which recalculates the pressure on the network, and goes to Pressure Optimization – a Valves subroutine where the program checks if node heads are below the established levels for the scenario, as seen in Table 2. If the heads are below the levels established, this subroutine will adjust the heads to the desired level and engage a pressure-reducing valve (PRV) on the pipe upstream of the node. In the same way, the data passes through Pressure Optimization - Pumps and the subroutine checks if the heads are under the desired level on the nodes and
Rev. Ambient. Água vol. 15 n. 2, e2455 - Taubaté 2020
Proposal of optimal operation strategy applied to … 5 engages a pump on the pipe upstream from the node. The optimization program considers only the pressures downstream of the pumps and valves implemented for the calculations.
Table 2. Codified and real work levels employed in simulation. Parameters Factor Unity Work Levels -2* -1* 0* 1* 2* Diameter A m 0.1375 0,25 0.3625 0.475 0.5875 Reservoir head B m 797.50 815,00 832.50 850.00 867.50 Pump head C m.c.a. 7.50 15,00 22.50 30.00 37.50 Valve head D m.c.a. 20.00 30,00 40.00 50.00 60.00 *Note: The asterisk indicated values is codified form.
Finally, the pressure values of the network go to the hydraulic recalculation subroutine and then it is verified that the pressures are within the limits established for the nodes, as shown in Table 2. If they are within the limits, the pressure values at the nodes and the sections where the pumps and valves were implemented are printed until the end of the algorithm iterations Figure 3.
Figure 3. Flowchart of optimization genetic algorithm with hydraulic calculation module.
For calculation of losses, an approach of Tucciarelli et al., (1999) was chosen, which points out a correlation of water losses in a network with pressures is an equation which considers the small leaks surround each node and the force of the water pressure, as found in Silva (2003), where losses are represented in percentages and average pressure (Pmedia), arithmetic average
Rev. Ambient. Água vol. 15 n. 2, e2455 - Taubaté 2020
6 Alex Takeo Yasumura Lima Silva et al. of pressures in network nodes. Equation 1 is adjusted to represent a Brazilian average leak rate, which is approximately 40% according the Brazilian water and sewer services report (SNIS, 2019).
푛ó푠 0,5 ∑푖=1 푃푒푟푑푎푠 = 푃푚푒푑푖푎 × 7,27 (1) Operational levels of factors (variables) involved in loss calculation were obtained by the Design of Experiments technique, employing Montgomery’s adapted factorial approach (Montgomery, 1999); this is, where the quantity of experiments to be achieved is given for 2k, where k is the number of variables, and also includes central and axial points, as per Table 2, which results in 32 scenarios to simulate. The second-order model, for regression analysis and obtaining surface response, is based on an Equation 2 employed in study of Kanigalpula et al. (2016).
̂ ̂ k ̂ k ̂ 2 k−1 k ̂ Y = β0 + ∑i=1 βiXi + ∑i=1 βiiXi + ∑i=1 ∑ i Where Y is the answer to be obtained, X1, X2, ..., Xj are the independent variables with influence in response, 훽̂0, 훽̂i (i = 1, 2, ... , k), 훽̂ij (j = 1, 2, ..., k) are estimated parameters and ε is a random error of the experiment. The codification of the variables, that is, the transformation of the same numeric values for levels (-2, -1, 0, 1 and 2) is given by Equation 3. 푋 −푋 푥 = 푖푢 푖 , 푓표푟 푢 = 1, 2, … , 푁 푎푛푑 푖 = 1, 2, … , 푘 (3) 푖푢 푠 푥푖 Where: ● 푋푖푢 = u-th level of the ith independent variable; 푋 ● 푋̅ = ∑푁 푖푢 Is the average of the values 푋 ; 푖 푢−1 푁 푖푢 1 (푋 −푋̅̅̅)2 2 ● 푠 = [∑푁 푖푢 푖 ] Is the standard deviation; 푥푖 푢=1 푁 ● N = number of observations. For obtaining estimated parameters, the ordinary least squares method was used, as per Rossi and Neves (2014), by Equation 4: 훽̂ = (푋푇푋)−1푋푇푦 (4) Where, in Equation 5 sources which compound least squares method can be observed. 푋 = [푥 푥 ⋱ 푥 푥 ], 훽̂ = [훽̂ ̂ ̂ ] and 푌̂ = [푌̂ 푌̂ 푌̂ ] 11 ⋯ 1푛 ⋮ ⋮ 푛1 ⋯ 푛푛 1 훽2 ⋮ 훽푛 1 2 ⋮ 푛 (5) Being X the codified experimental matrix, 훽̂ the matrix of coefficients to be estimated and 푌̂ the matrix with obtained responses (results). For obtaining an optimal point, the electronic chart with algorithm of optimization Generalized Reduced Gradients was used to, by response surface equation, obtain optimal responses for problems by minimization of equations. 4. RESULTS AND DISCUSSION Simulations carried out for the complete factorial experiment obtained an average loss of 41.01%. In scenarios 12, 16, 22 and 24, there was a deterioration of network conditions, with Rev. Ambient. Água vol. 15 n. 2, e2455 - Taubaté 2020 Proposal of optimal operation strategy applied to … 7 worsening of water losses. On the other hand, the best scenarios were numbers 1, 3 and 9, as displayed in Figure 4. Figure 4. Result of simulated scenarios. Using the results of simulated scenarios, Equation 6 was achieved, the result of the complete factorial experiment: 푌̂(%) = (0,4101 + (퐴 × 0,1942) + (퐵 × 0,015542) + (퐶 × 0,025208) + (퐷 × 0,022808) − (퐴2 × 0,008494) − (퐵2 × 0,006106) + (퐶2 × 0,00394) − (퐷2 × 0,007656) + (퐴 × 퐵 × 0,007463) − (퐴 × 퐶 × 0,010187) + (퐴 × 퐷 × 0,010637) − (퐵 × 퐶 × 0,006375) + (퐵 × 퐷 × 0,00695) − (퐶 × 퐷 × 0,002275)) × 100 (6) The analysis of interferences of each factor individually shows what influences losses the most is the variation of pumping head levels, while what influences the least is the variation of reservoir heads, as displayed in Figure 5. Figure 5. Analysis of individual interactions of factors. Analysis of interactions between factors shows that interactions between the piping diameter and the pumping pressure cause a major reduction of water losses in the network, while interactions between the piping diameter and the reservoir head cause a major increase of losses. Interactions between the pumping head and valve head have little statistical significance, as per Figure 6, where the X axis is the factor level, and Y axis the losses. Rev. Ambient. Água vol. 15 n. 2, e2455 - Taubaté 2020 8 Alex Takeo Yasumura Lima Silva et al. Figure 6. Analysis of interactions between variables. The equation-generated response surfaces of Figures 7, 8 and 9, also showing the behavior of response regarding factors for complete analysis. Figure 7. Response surfaces 1 and 2. Figure 8. Surface responses 3 and 4. Figure 9. Surface responses 5 and 6. Rev. Ambient. Água vol. 15 n. 2, e2455 - Taubaté 2020 Proposal of optimal operation strategy applied to … 9 The equation modelling the response in electronic chart was launched and then the optimization algorithm Generalized Reduced Gradients was employed to obtain decision variables; that is, codified values of factors A, B, C and D resulting in lower possible loss, respecting restriction of -2 to 2, minimum and maximum values of factors, making adjustments for an operational level closer to rule or commercial, as shown in Table 3. Table 3. Factors decoded to the optimal point. Factors Values applied (Decoded) Units A Diameter 0.30 M B Reservoir Head 818.97 M C Pump Head 10.00 M.W.C. D Valve Head 21.94 M.W.C. For such values, applied on optimization algorithms, expected loss was 27.86%. one factor which needed to be adjusted was factor C – Pump Head, once it was modified for 10 m.c.a., to meet rule NBR 12218 (ABNT, 2017), which set out that value of pressure as the required minimum in a water-distribution system. The value of the diameter was rounded to 0.300 m, the commercial value displayed by Porto (2006), and other factors were rounded to the second decimal place for launching the same in network optimization routines. Thus, the optimal scenario results appear in Figure 10. Figure 10. Results for optimal scenario. In this scenario, pumps were introduced in following pipes: Pipe 5: head of 26.19 m.w.c.; Pipe 8: head of 3.86 m.w.c.; Pipe 9: head of 47.03 m.w.c. A valve was also introduced in pipe 7, generating a head loss of 22.19 m.w.c. to keep the head at 21.94 m.w.c. Losses in this scenario were 26.61%, a reduction of 16.19 p.p. in relation to the scenario without optimization, a value situated within error R² of 89.12% for the response. This was within the range predicted by the equation of the model. Thus, this scenario defined the operational strategy for the network. 5. CONCLUSIONS The genetic algorithm of optimization obtained a good performance, being able to maintain pressures within established limits in the study and indicated the quantity of pumps and valves Rev. Ambient. Água vol. 15 n. 2, e2455 - Taubaté 2020 10 Alex Takeo Yasumura Lima Silva et al. employed, as well as pumping pressures or the head loss generated by the valves and portions of pumps and valve implantation. Thus, the planning of experiments proved to be a potential tool to assist in the operation optimization of a water distribution network, making possible optimization of the equation of obtained response surface and, consequently, obtention of optimal parameters and evaluation of interactions. However, more studies should be done to evaluate performance on more complex and real network scenarios to validate the tool under different conditions. 6. ACKNOWLEDGEMENTS The authors thanks FINEP Redecope Project - MCT (Ref. 0983/10) - Ministry of Science and Technology entitled "Development of efficient technologies for hydro management efficiency in water supply systems' program “Pesquisador Mineiro” Fapemig for the PPM - 00755-16 besides thanking NUMMARH - Nucleus of Modeling and Simulation in Environment and Water Resources and systems of unified. Thanks to CAPES for the master's scholarship number 1764063 to the author “Alex Takeo Yasumura Lima Silva". Thanks to CNPq for the scholarship of André Carlos da Silva 7. REFERENCES ABNT. Nbr 12.218: Projeto de rede de distribuição de água para abastecimento público. Rio de Janeiro, 2017. BARIMANI, S.; ROK, Š.; KLEINEBUDDE, P. Optimization of the semi-batch tablet coating process for the continuous manufacturing line by design of experiments. International Journal of Pharmaceutics, v. 539, 2017, p. 95-103, 2018. https://dx.doi.org/10.1016/j.ijpharm.2018.01.038 BI, W.; DANDY, G. C.; MAIER, H. R. Improved genetic algorithm optimization of water distribution system design by incorporating domain knowledge. Environmental Modeling & Software, v. 69, p. 370-381, 2015. http://dx.doi.org/10.1016/j.envsoft.2014.09.010 CANDELIERI, A.; ARCHETTI, F.; MESSINA, E. Improving leakage management in urban water distribution networks through data analytics and hydraulic simulation. WIT Transactions on Ecology and the Environment, v. 171, p. 107-117, 2013. http://doi:10.2495/WRM130101 CHINI, C. M.; STILLWELL, A. S. The State of U. S. Urban Water: Data and the Energy-Water Nexus. Water Resources Research, v. 54, n. 3, p. 1796-1811, 2018. http://10.1002/2017WR022265 COELHO, B.; ANDRADE-CAMPOS, A. Efficiency achievement in water supply systems - A review. Renewable and Sustainable Energy Reviews, v. 30, p. 59-84, 2014. http://dx.doi.org/10.1016/j.rser.2013.09.010 CREACO, E.; PEZZINGA, G. Embedding linear programming in multi objective genetic algorithms for reducing the size of the search space with application to leakage minimization in water distribution networks. Environmental Modeling and Software, v. 69, p. 308-318, 2015. http://dx.doi.org/10.1016/j.envsoft.2014.10.013 FONTANA, N.; GIUGNI, M.; PORTOLANO, D. Losses reduction and energy production in water-distribution networks. Journal of Water Resources Planning and Management, v. 138, p. 237–244, 2012. https://doi.org/10.1061/(ASCE)WR.1943-5452.0000179 Rev. Ambient. Água vol. 15 n. 2, e2455 - Taubaté 2020 Proposal of optimal operation strategy applied to … 11 GOMES, J. H. F. Mixture canonical polynomial method for multi-objective optimization. 2013. Thesis (Doctorate in Production Engineering) - Federal University of Itajubá, Itajubá, 2013. HAN, R.; LIU, J. Spectral clustering and genetic algorithm for design of district metered areas in water distribution systems. Procedia Engineering, v. 186, p. 152–159, 2017. https://doi.org/10.1016/j.proeng.2017.03.221 KANAKOUDIS, V.; MUHAMMETOGLU, H. Urban water pipe networks management towards non-revenue water reduction: two case studies from Greece and Turkey. Clean, v. 42, p. 880–892, 2014. http://dx.doi.org/10.1002/clen.201300138 KANIGALPULA, P. K. C. et al. Experimental investigations, input-output modeling and optimization for electron beam welding of Cu-Cr-Zr alloy plates. International Journal of Advanced Manufacturing Technology, v. 85, p. 711-726, 2016. http://dx.doi.org/10.1007/s00170-015-7964-7 KHATAVKAR, P.; MAYS, L. W. Model for Optimal Operation of Water Distribution Pumps with Uncertain Demand Patterns. Water Resources Management, v. 31, p. 3867–3880, 2017. http://dx.doi.org/10.1007/s11269-017-1712-8 LIU, J.; LI, X.; YANG, H.; LIU, JUNGUO; ZHENG, C.; ZHENG, YAN. The Water-Energy Nexus of Megacities Extends Beyond Geographic Boundaries: The Case of Beijing. Environmental Engineering Science, v. 36, n. 7, 2019. http://10.1089/ees.2018.0553 MONTGOMERY, D. C. Experimental Design for Product and Process Design and Development. Journal of the Royal Statistical Society: Series D, v. 48, p. 159-177, 1999. https://doi.org/10.1111/1467-9884.00179 MUTIKANGA, H. E.; SHARMA, S. K.; VAIRAVAMOORTHY, K. Methods and tools for managing losses in water distribution systems. Journal of Water Resources Planning and Management, v. 139, n. 2, p. 166–174, 2013. http://dx.doi.org/10.1111/j.1747- 6593.2010.00225 OIKONOMOU, K.; PARVANIA, M. Optimal Coordination of Water Distribution Energy Flexibility with Power Systems Operation. IEEE Transactions on Smart Grid, v. 10, p. 1101-1110, 2018. https://doi.org/10.1109/TSG.2018.2824308 PORTO, R. M. Hidráulica Básica. 4. ed. São Carlos: EESC/USP, 2006. ROSSI, J. W.; NEVES, C. Econometrics and time series with applications to data from the Brazilian economy. Rio de Janeiro: LTC, 2014. SANZ, G.; PÉREZ, R.; KAPELAN, Z.; SAVIC, D. Leak detection and localization through demand components calibration. Journal of Water Resources Planning and Management, v. 142, n. 2, p. 159-164, 2016. http://dx.doi.org/10.1061/(ASCE)WR.1943-5452.0000592 SILVA, F. G. B. Calibration studies of water distribution networks through genetic algorithms. 2003. Thesis (Doctorate in Hydraulics and Sanitation) - São Carlos School of Engineering, University of São Paulo, São Carlos, 2003. SISTEMA NACIONAL DE INFORMAÇÕES SOBRE SANEAMENTO (Brasil). Diagnóstico dos serviços de água e esgoto - 2017. Brasília, 2019. Available at: http://www.snis.gov.br/diagnostico-agua-e-esgotos/diagnostico-ae-2017 Rev. Ambient. Água vol. 15 n. 2, e2455 - Taubaté 2020 12 Alex Takeo Yasumura Lima Silva et al. SOLER, E. M. et al. Optimization of electrical energy costs in the scheduling of catchment, storage, and distribution of water. Production, v. 26, n. 2, p. 385-401, 2016. https://doi.org/10.1590/0103-6513.146113 TANYIMBOH, T. T.; SEYOUM, A. G. Efficient parallel evolutionary optimization algorithm applied to the water distribution system. European Water, v. 58 p. 375-381, 2017. TUCCIARELLI, T.; CRIMINISI, A.; TERMINI, D. Leak Analysis in Pipeline Systems by means of Optimal Valve Regulation. Journal of Hydraulic Engineering, v. 125, p. 277- 285, 1999. https://doi.org/10.1061/(ASCE)0733-9429(1999)125:3(277) VAKILIFARD, N. et al. The role of water-energy nexus in optimising water supply systems - Review of techniques and approaches. Renewable and Sustainable Energy Reviews, v. 82, p. 1424-1432, 2018. http://dx.doi.org/10.1016/j.rser.2017.05.125 YU, P.; LOW, M. Y.; ZHOU, W. Trends in Food Science & Technology Design of experiments and regression modeling in food flavour and sensory analysis: a review. Trends in Food Science & Technology, v. 71, p. 202-215, 2018. https://doi.org/10.1016/j.tifs.2017.11.013 Rev. Ambient. Água vol. 15 n. 2, e2455 - Taubaté 2020 Ambiente & Água - An Interdisciplinary Journal of Applied Science ISSN 1980-993X – doi:10.4136/1980-993X www.ambi-agua.net E-mail: [email protected] Physical and chemical attributes of soil on gully erosion in the Atlantic forest biome ARTICLES doi:10.4136/ambi-agua.2459 Received: 24 Aug. 2019; Accepted: 26 Jan. 2020 João Henrique Gaia Gomes1 ; Marcos Gervasio Pereira2* ; Márcio Rocha Francelino3 ; João Pedro Bessa Larangeira2 1Instituto de Agronomia. Departamento de Solos. Programa de Pós-Graduação em Agronomia. Universidade Federal Rural do Rio de Janeiro (UFRRJ), BR 465, km 7, CEP: 23897-000, Seropédica, RJ, Brazil. E-mail: [email protected] 2Instituto de Agronomia. Departamento de Solos. Universidade Federal Rural do Rio de Janeiro (UFRRJ), BR 465, km 7, CEP: 23897-000, Seropédica, RJ, Brazil. E-mail: [email protected] 3Departamento de Solos. Universidade Federal de Viçosa (UFV), Av. P H Rolfs, S/N, CEP: 36570-900, Viçosa, MG, Brazil. E-mail: [email protected] *Corresponding author. E-mail: [email protected] ABSTRACT Soil is a fundamental natural resource for subsistence and development of humanity, exploited mainly for agriculture. Agricultural practices, though, are improperly performed, compromising edaphic conditions and favoring erosive processes, which mainly culminate in the loss of soil and nutrients. Water erosion represents the main form of soil degradation, given that the impact of raindrops on the soil results in the detachment of particles, a process favored by factors such as climate, relief, soil vegetation and use and occupation. The objective of the study was to classify four gullies based on their evolutionary turns and to judge the physical- chemical classifications of the soil at the internal and external faces of the gullies. The morphology of the gullies was classified by aerial images generated by drones. The gullies were mapped using Google Earth images from 2016. The qualitative assessment was performed using the digital field-elevation curvature (MDESC) model with field validation. Deformed samples were collected at depths of 0-10 and 10-20 cm, while non-deformed samples were collected at depths of 0.0-0.10 cm to evaluate their chemical and physical attributes. A nonparametric 5% Kruskal-Wallis statistical analysis was performed on the resulting data. The chemical and physical attributes of the soil differed according to the evolutionary stage of the surfaces (internal and external) at depths of 0 to 10 cm, while the faces showed differences in depth of 10 to 20 cm. Keywords: erosive process, geotechnologies, soil quality indicators. Atributos físicos e químicos em voçorocas no Bioma da floresta Atlântica RESUMO O solo é um recurso natural fundamental para a subsistência e desenvolvimento da humanidade, sendo principalmente explorado pela agricultura, cujas práticas inadequadas comprometem as condições edáficas, favorecendo a ocorrência de processos erosivos, que This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 João Henrique Gaia Gomes et al. culminam principalmente na perda de solo e nutrientes. A erosão hídrica atua como principal forma de degradação do solo, em que, a partir da ação do impacto da gota de chuva sobre o solo, ocorre o desprendimento de partículas que, associadas a fatores como clima, relevo, solo vegetação e uso e ocupação, favorecem esse processo. O objetivo do estudo foi classificar quatro voçorocas com base em seus estágios evolutivos e julgar as classificações físico- químicas do solo nas faces internas e externas das voçorocas. A morfologia das voçorocas foi classificada por imagem aérea gerada por drone. As voçorocas foram mapeadas usando imagens do Google Earth a partir de 2016. A avaliação qualitativa foi realizada usando o modelo digital de curvatura de elevação de campo (MDSC) com validação de campo. Amostras deformadas foram coletadas nas profundidades de 0-10 e 10-20 cm, enquanto amostras não deformadas foram coletadas em profundidades de 0-10 cm para avaliar seus atributos químicos e físicos. De posse dos dados foi realizada análise estatística não paramétrica de Kruskal-Wallis a 5%. Os atributos químicos e físicos do solo diferiram de acordo com o estágio evolutivo nas faces (interna e externa) em profundidades de 0 a 10 cm, enquanto as faces mostraram diferenças em profundidade de 10 a 20 cm. Palavras-chave: geotecnologias, indicadores de qualidade do solo, processos erosivos. 1. INTRODUCTION A lack of technical information related to agricultural expansion has led to various forms of environmental damage. Agricultural development continues to have numerous effects on natural ecosystems, as best practices for environment conservation are not widely implemented. Previous studies (Laurance et al., 2014) have shown that problems in agriculture can negatively affect human well-being and environmental conservation. Humans have a large impact on the environment (Ferreira et al., 2016) by affecting soil occupation, use, and management. Inadequate agricultural practices can damage the physical and chemical attributes of soil, affect water dynamics, and have various other consequences. According to Santos et al. (2017), improper management can lead to soil sealing, which increases surface runoff and, consequently, mass runoff. Water erosion is one effect of improper management and greatly contributes to soil degradation. Bogunovic et al. (2018) described erosion as one of the main precursors of soil degradation. Erosion typically begins as raindrops impacting the soil, causing aggregates to rupture into individualized particles, which are more easily carried along the landscape by surface and subsurface runoff. Linear erosion refers to the beginning of the erosive process, which can become laminar and evolve into a gully. The different proportions, dimensions, vegetation cover, and water dynamics are used to classify the gullies according to their morphology and evolutionary stages as initial, juvenile, mature, or senile (Dobek et al., 2011). Gullies, which are defined as a result of an erosive process that removes soil mass and nutrients in an advanced stage, are found throughout the Cachimbal River sub-basin, that comprises a large part of the territorial extension of the municipality of Pinheiral, in the state of Rio de Janeiro – Brazil, which is the area of study. According to studies carried out in the area (Menezes et al., 2010; Santos et al., 2017), the occurrence of gullies may be associated with different forms of soil usage, occupation, and management. Hence, this study hypothesized that edaphic attributes present differentiated patterns according to the evolutionary stages and (inner and outer) surface of the gully. The present study therefore aims to classify and evaluate the gullies based on their evolutionary stage and the physical and chemical attributes of the soil in their inner and outer surfaces. Rev. Ambient. Água vol. 15 n. 2, e2459 - Taubaté 2020 Physical and chemical attributes of soil on … 3 2. MATERIALS AND METHODS The study was carried out in the Cachimbal River sub-basin, which composes a large part of the municipality of Pinheiral, Rio de Janeiro - Brazil (Figure 1). This sub-basin is in the region of Médio Paraíba Fluminense and makes up the Paraíba do Sul River basin. Figure 1. Sub-basin of Cachimbal Stream, Pinheiral - RJ. The climate in the study area is classified as “temperate”, with dry winters and rainy summers (Cwa), and rainy tropical climate with dry winters (Am), according to the Koppen climate classification (Alvares et al., 2014). The vegetative cover is currently comprised of implanted, spontaneous, and unmanaged pastures, which are degraded. During the colonial period in late 18th century, because of intense use and occupation, the region that once contained Floresta Estacional Semidecidual Submontana as its original vegetation underwent changes and this was replaced by coffee plantations. (Menezes et al., 2010). The predominant soils in the Cachimbal Creek sub-basin are on the hillside, Ultisol (Argissolos Vermelho-Amarelos) and Inceptisol (Cambissolo Háplico), and summit and backslope of the hillside, Oxisol (Latossolos Vermelho-Amarelos) (Santos et al., 2017). According to Santos et al. (2016), the sub-basin’s altitude varies from 360 m at the mouth of the Cachimbal Stream to 720 m in the Arrozal mountain range. Approximately 72% of the sub- basin is comprised of hillsides with slopes, 22.3% of narrow cultivated plains, and 5.7% of hilltop areas. The gullies were mapped using 2016 Google Earth images with a spatial resolution of 2.34 m. In the images, four gullies were georeferenced to occur in convex pedoforms at different evolutionary stages, as in the Ribeirão Cachimbal sub-basin, where gullies generally have this topographic feature (pedoform) (Gaia-Gomes, 2017). Qualitative classification was conducted using a digital model surface curvature (Figure Rev. Ambient. Água vol. 15 n. 2, e2459 - Taubaté 2020 4 João Henrique Gaia Gomes et al. 2), which was generated using topographic charts of the municipalities of Volta Redonda (Sheet SF-23-ZAV-2) and Piraí (Sheet SF - 23-Z-VI-1), obtained from IBGE on the scale of 1:50,000, with a spatial resolution of 10 m on the scale of 1:100,000, via ArcGIS 10.5. The coordinates of the identified gullies were plotted using DMSC; after a convex surface emerged, and the results were validated through field analysis. Figure 2. Digital Model of Sub-basin of Cachimbal Stream, Pinheiral - RJ. A flight using the Drone model Phantom 4 was performed on an exposure strand with four gullies that emerged in a convex pedoform (Figure 3). In such pedoform, the gullies were classified according to their morphology as initial, juvenile, mature, or senile (Dobek et al., 2011; Cherobin, 2012). The selected gullies were divided according to their inner and outer surfaces. Deformed samples were collected at depths of 0–10 and 10–20 cm and non-deformed samples were collected at depths of 0–10 cm to evaluate their chemical and physical attributes. In the gully classified as initial, 10 deformed and 10 non-deformed samples were collected; in the juvenile gully, 12 deformed and 12 non-deformed samples were collected; in the mature gully, 16 deformed and 16 non-deformed samples were collected; and in the senile, 18 deformed and 18 Rev. Ambient. Água vol. 15 n. 2, e2459 - Taubaté 2020 Physical and chemical attributes of soil on … 5 non-deformed samples were collected at both depths. The Kopeck ring was used to collect the non-deformed samples. Figure 3. Gullies in different evolutionary stages in the selected exhibition area. After collection, the deformed samples were dried, discharged, and passed through a 2- mm sieve to obtain an air-dried thin earth sample according to the method reported by Santos et al. (2015). The values of pH in water and Ca2+, Mg2+, Al3+, K+, Na+, P, H+Al contents were determined as described by Teixeira et al. (2017). Total organic carbon (TOC) contents were quantified according to Yeomans and Bremner (1988). S values (sum of the Ca+2, Mg+2, K+, and Na+ contents), T values were calculated, and V% was estimated according to Teixeira et al. (2017). For physical attributes, bulk density (Bd), particle density (Pd) and total porosity volume (TPV) were calculated as described by Teixeira et al. (2017). Particle size analysis was carried out to quantify the following soil fractions: total sand (g kg-1), coarse sand (g kg-1), fine sand (g kg-1), total clay (g kg-1), natural clay (g kg-1), and silt (g kg-1) (Teixeira et al., 2017). Based on the results of granulometric analysis, the degree of flocculation (DF%) were calculated as described by Teixeira et al. (2017). After identifying and classifying the evolutionary stages of the gullies, the possible differences between the evolutionary stages and faces of the gullies were evaluated by the Kruskal-Wallis test, at a 5% significance level. To evaluate the correlations between variables in the gullies, the Pearson correlation test was performed. A p-value <0.05 was considered to indicate a statistically significant difference. The XLSTAT software was used for the analysis. Principal component analysis was carried out using the XLSTAT program to determine which chemical and physical variables could be used to indicate similarity or dissimilarity among the evolutionary stages and faces of the gullies. 3. RESULTS AND DISCUSSION The curvature surface, with the flat category represented the largest percentage of the sub- basin area (59.3%). The lowest area value was observed in the concave category (19.1%). The convex category represented (21.6%) of the total area. According to Arthur et al. (2014), concave, flat, and convex surfaces influence sediment production and intensity and direction of water flow in the soil profile. According to Aumond et al. (2014), concave surfaces are characterized by microclimatic, topographic, and solar radiation conditions directed towards the interior, promoting greater concentration of matter Rev. Ambient. Água vol. 15 n. 2, e2459 - Taubaté 2020 6 João Henrique Gaia Gomes et al. and energy. Additionally, water, sediment, mineral, and organic matter accumulation can occur in this pedoform. The convex pedoform showed different water dynamics in which the surface runoff of water and sediments was associated with the external and internal flow of matter and energy, leading to energy dissipation and losses caused by erosion and leaching (Aumond et al., 2014). The chemical and physical attributes of soil at a depth of 0–10 cm are presented in Table 1. Regarding the granulometric fractions for natural clay, differences were observed between the juvenile and mature stages and between the juvenile and senile stages on the outer surface. Among these, differences were observed only in the juvenile stage, with the highest values occurring for the inner surface. This pattern may be associated with the stabilization process that tends to occur between the mature and senile stages, in which particle drifts occur more slowly, in contrast to those in the juvenile stage in which more intense erosion is observed and causes greater removal of sediments. For the total clay fraction, differences between the initial and mature, initial and senile, juvenile and mature, and juvenile and senile stages on the outer face were observed, with the highest values quantified for the outer face of mature and senile gullies. Differences were observed between the initial stages of the erosive process (initial and juvenile) and transition/stabilization process (mature and senile). Fractions of smaller granulometry, such as clay, may develop with lower intensity in the transition/stabilization processes, as their surface runoff occurs to a lesser extent because of the presence of vegetation cover and colonization of plant species from mass flow. The highest values of the flocculation degree were observed for the outer face of the juvenile gully, showing large differences between the initial and juvenile and between the juvenile and senile stages. The internal and external faces of the initial and senile stages showed significant differences. Flocculation degree is inversely proportional to the natural clay content, and soils with lower values are more vulnerable to water erosion (Lima et al., 2013). The observed pattern may be related to the removal of naturally dispersed clay particles via the erosive process, in which only flocculated particles remain, increasing the degree of flocculation. According to Ayer et al. (2015), lower levels of flocculation occur when soil conservation methods are not implemented and because of inadequate management, favoring the destruction of aggregates and reduction of soil permeability. For the total sand fraction, the highest values were observed for the inner face of the initial gully. The same pattern was observed for coarse sand. The gullies classified as initial and senile presented differences between themselves and for the two physical attributes mentioned above on the inner face. Differences were observed on the inner face of gullies in the initial and mature stage and in the juvenile and mature stages, which did not corroborate the results for the coarse sand fraction for which only a difference between the juvenile and mature stages was found. On the faces, differences were only observed for the mature gully. The observed pattern may be associated with surface runoff, which tends to occur with greater intensity in the initial and juvenile stage, carrying particles from the outer to the inner face, which remain stationary inside the gully until water dynamics modify this pattern. The lowest values of the fine sand fraction were observed for the inner face of the mature gully. Differences were found for both faces between the initial and mature stages and on the external face between juvenile and mature stages as well as juvenile and senile stages. Lower values of fine sand are also related to surface runoff. Granulometry fractions with smaller diameters require less kinetic energy to be transported. This attribute was weak in the gully classified as mature, but strengthened in the senile stage, indicating that a transitional stage occurred followed by stabilization (Table 1). Rev. Ambient. Água vol. 15 n. 2, e2459 - Taubaté 2020 Physical and chemical attributes of soil on … 7 Table 1. Averages of the chemical and physical attributes of the soil of the initial, juvenile, mature and senile gullies at 0-10 cm depth on the inner (I) and outer (E) faces. pH Ca Mg+2 -1 Stages (cmolc kg ) I E I E I E Initial 5.01aA 4.98aA 0.99cA 0.97bB 1.15aA 1.18aA Juvenile 4.94aA 4.76bA 1.16bA 1.12abA 1.11abA 1.16aA Mature 4.89aA 4.84abA 1.21abA 0.96bA 0.97bcB 1.03aA Senile 4.99aA 4.98aA 1.26aA 1.28aA 0.87cA 0.86bB Al3+ H+Al Na+ -1 Stages (cmolc kg ) I E I E I E Initial 0.81aB 0.99bA 1.75bA 2.42abA 0.010aA 0.010aA Juvenile 0.97aA 1.24aA 2.13abA 2.12aA 0.010aA 0.010aA Mature 1.08aA 1.12abA 1.54bA 2.44bA 0.010aA 0.010aA Senile 0.98aA 0.99bB 2.47aA 2.92aA 0.010aA 0.010aA K+ TOC S Value -1 -1 -1 Stages (cmolc kg ) (g kg ) (cmolc kg ) I E I E I E Initial 0.010aA 0.012aA 6.57bB 10.38aA 2.20aA 2.14abA Juvenile 0.010abA 0.011aA 12.51aA 13.75aA 2.30aA 2.30aA Mature 0.009bcA 0.008aB 10.65abA 13.12aA 2.20aA 2.17bA Senile 0.008cB 0.007bA 13.42aA 14.20aA 2.18aA 2.16abA T Value V Total Clay -1 -1 Stages (cmolc kg ) (%) (g kg ) I E I E I E Initial 4.50abA 4.77bcA 56.00aA 45.00aA 263.00aA 252.00cB Juvenile 4.430abA 5.32aA 53.50abA 43.40aA 301.00aA 284.70bcB Mature 4.34bA 4.47cA 61.63aA 45.70aA 336.70aA 372.31aA Senile 4.00aA 5.08abA 47.35bA 45.00aA 263.25aA 334.56abA Natural Clay FG Total sand Stages (g kg-1) (%) (g kg-1) I E I E I E Initial 101.90aA 75.30abA 61.71aB 69.10bA 576.80aA 532.70abA Juvenile 131.65aA 37.00bB 51.81aA 86.38aA 516.90abA 540.00aA Mature 124.81aA 97.20aA 60.36aA 73.61abA 477.31abA 421.13cB Senile 101.40aA 104.25aA 56.40aB 68.68bA 425.65bA 428.38bcA Fine Sand Coarse Sand Silt Stages (g kg-1) I E I E I E Initial 129.20aA 133.80abA 447.20aA 398.90abA 160.20bB 214.50aA Juvenile 131.82abA 138.83aA 385.10abA 403.70aA 181.20bA 175.30aB Mature 96.87bA 88.75cB 380.40abA 332.40bA 186.10bB 206.60aA Senile 103.50abA 100.31bcB 322.20bA 337.30abA 311.10aA 237.10aA Bd Pd TPV Stages (Mg m-3) (%) I E I E I E Initial 1.12abA 1.47aA 2.48aA 2.37aA 54.60aA 37.70aA Juvenile 1.10bB 1.42aA 2.39aA 2.36aA 55.72aA 39.60aA Mature 1.14bB 1.44aA 2.35abA 2.26aA 51.56aA 35.88aA Senile 1.28aA 1.43aA 2.28bB 2.33aA 43.80bA 38.44aB Equal lowercase letters in the column concern evolutionary stages and equal uppercase letters in the row are inner and outer surfaces, and do not differ by the Kruskal-Wallis test at 5% significance. I: inner face of the gullies; E: outer face of the gullies; TOC: Total Organic Carbon; Bd: bulk density; Pd: Particles density; TPV: Total Porosity Volume. For the silt fraction, the highest value was observed for the inner face of the senile gully, showing a difference between the initial and senile, juvenile and senile, and mature and senile Rev. Ambient. Água vol. 15 n. 2, e2459 - Taubaté 2020 8 João Henrique Gaia Gomes et al. stages. Between faces, differences were observed for the initial, juvenile and mature stages. Like the fine sand fraction, silt is one of the fractions most susceptible to disaggregation and transport (Albuquerque et al., 2013). Analysis of bulk density (Bd) values revealed higher values for the outer face of the gullies. Differences were detected between the juvenile and senile stages and between mature and senile stages in the inner face. A difference was also observed between the faces of the gullies in the juvenile and mature stages. The soil structure influences its Bd, making it possible to predict the impacts of erosive processes. In general, higher values of Bd are related to a high degree of soil compaction. Compaction is directly proportional to Bd, which results in lower porosity, reducing the internal flow of water and favoring superficial runoff. The area has a long history of use and occupation for coffee cultivation and pasture, possibly contributing to the increased Bd which, according to Sousa Neto et al. (2014), is normally higher in managed areas possibly because of soil compaction. Compared to other gully types, the senile gully has larger dimensions and a greater depth, resulting in higher Bs values inside. For the particle density (Pd), differences were observed between the initial and senile and between the juvenile and senile stages for the inner face, as well as between faces in the senile stage. Schjønning et al. (2017) predicted soil particle density from organic matter and clay contents and found that a higher organic matter content was associated with lower Pd values. The highest total porosity volume (TPV) values were found for the inner face of the gullies. Deng et al. (2016) observed a similar pattern when studying the effect of land use on the physical and chemical properties of soils and erodibility in gully sediments in the municipality of Anxi, China. Differences were observed in the internal face between the initial and senile, juvenile and senile, and mature and senile gullies. The faces differed in the gullies classified as senile, where a higher value was observed for the inner face. Mass runoff originating from the erosive process culminates in soil disintegration, altering the soil porosity distribution that initiates restructuring on the inner side of the gully in the senile stage, since it is under spontaneous and natural regeneration. The highest pH values were found for the inner side of the gullies, while the highest values were found in the initial gully, with a difference between the initial and juvenile as well as between juvenile and senile stages. For exchangeable Al3+ values, the same pattern was observed as for pH between stages, but with smaller values for the inner face. This pattern was also observed in the faces of the initial and senile gullies, which also showed differences. The values of TOC followed the same pattern as H+Al, with higher values of TOC observed for the senile stage and on the outer face, which may be associated with the addition of organic matter from the vegetation at this evolutionary stage. For this attribute, a difference was observed between the initial and juvenile as well as between the initial and senile stages on the inner face. For H+Al, there were differences between the initial and senile stages as well as between the mature and senile stages on the inner face, and between the juvenile and mature and the mature and senile stages on the outer face. For Ca2+, the highest values were observed for the gully going through the senile stage, showing the same pattern as TOC contents, which may be associated with the decomposition of vegetable material originating from the vegetation present on the surface of this gully. The Ca2+ values differed between the initial and senile stages and between the juvenile and senile stages on the inner face, as well as between the initial and senile stages and between the mature and senile stages on the outer face. A difference in the faces was detected in the initial stage. For the Mg2+ and K+ values, the largest values were observed in the outer face of the gullies, with the highest ones in the initial stage. When this attribute was compared, according to the evolutionary stage of the gullies, a difference was observed between the initial and mature Rev. Ambient. Água vol. 15 n. 2, e2459 - Taubaté 2020 Physical and chemical attributes of soil on … 9 stages, initial and senile stages, and juvenile and senile stages on the inner face and between the initial and senile stages, juvenile and senile stages, and mature and senile stages on the outer face. The faces differed between the mature and senile stages. The observed pattern may be related to the absorption of these nutrients by the plants found on the inner face and edges of the gully in the senile stage. Lower S values were observed in the senile stage, while higher values were observed in the outer face. A difference between the juvenile and mature stages was only found on the outer face, which may be related to leaching losses. The T and V (%) values differed between the mature and senile stages on the inner face. For the T value in the outer face, differences between the initial and juvenile stages and between the juvenile and mature stages were observed. The highest value was observed in the outer face of the juvenile gully, differing from the one observed in V (%), in which the highest value was found in the outer face of the gully in mature stage. These results can be attributed to the decomposition and mineralization processes that develop at different intensities because of the characteristics of each stage, water dynamics, surface runoff, and availability of organic matter (Machado et al., 2010; Gomide et al., 2011). No differences were observed between the evolutionary stages and faces in Na+ contents. Figure 4 shows the results of the analysis of the main components (PCA) and Table 2 shows the values of the correlations between chemical and physical attributes of the soil and axes at a depth of 0–10 cm, showing a significant correlation at 5% in the Pearson test. The soil variables pH, Ca2+, Al3+, Na+, S value, total clay, and natural clay at 0–10 cm depth were not significantly correlated at a cut-off of 5% in the Pearson test. Figure 4. PCA for chemical and physical variables of the soil in the four evolutionary stages and internal and external faces of the gullies in depth of 0-10 cm. The PCA analysis showed that, for the relationship between the 1 and 2 axes, there was a separation in the chemical and physical attributes of the soil among the evolutionary stages and on the inner and outer faces (II: inner face of the initial stage, IE: outer face of the initial stage, JI: inner face of the juvenile stage, JE: outer face of the initial stage; MI: inner face of the mature stage, ME: outer face of the mature stage, SI: inner face of the senile stage, SE: outer face of Rev. Ambient. Água vol. 15 n. 2, e2459 - Taubaté 2020 10 João Henrique Gaia Gomes et al. the senile stage). The sum of the two axes explained the value of 84.78%, with axis 1 explaining 55.24% and axis 2 explaining 29.54%. Table 2. Values of the correlations between the soil’s chemical and physical attributes of the soil and the axes in depth of 0-10 cm in the analyzed stages. Chemical Attributes Axis Mg2+ H+Al TOC T Value V (%) 1 0.58 -0.79 -0.87 -0.70 0.82 2 0.72 0.55 -0.09 0.60 -0.50 Physical Attributes Axis Total Sand Fine Sand Coarse Sand DF Silt 1 0.76 0.45 0.82 -0.44 -0.65 2 0.64 0.76 0.55 -0.72 -0.45 Axis Bd Pd TPV 1 -0.80 0.90 0.87 2 0.46 0.22 -0.35 For stage II, the variables for coarse sand (r = 0.82), total sand (r = 0.76), and Pd (r = 0.90) were associated, correlating positively with axis 1, and variables Mg (r = 0.72) and fine sand (r = 0.76) correlated positively with axis 2. Regarding JI and MI, the most associated variables were TPV (r = 0.87) and V% (r = 0.82), which showed a positive correlation. The variables most associated with IE and JE, DF (r = 0.72) correlated positively with axis 2 and Bd (r = 0.80) showing a positive correlation, while H+Al (r = 0.79) and the T value (r = -0.70) showed a negative correlation with axis 1. For the ME, SE, and SI stages, the most associated variables were TOC (r = -0.87) and silt (r = -0.65), which showed a negative correlation with axis 1. Analysis of axis 1 verified that although there was a division among stages, the internal face of the gully classified as senile (SI) presented a different distribution pattern than the other stages. The interior of the gullies is a modified environment, in which the erosive process of mass drainage has already occurred and may present changes compared to the outer face. Arthur et al. (2014) and Santos et al. (2016) found that small variations in relief forms influence the variability in edaphic factors. The pattern observed in SI may be associated with spontaneous natural regeneration that occurs in the interior, which is the only parameter showing this pattern. Regeneration tends to improve soil quality by altering fertility, aeration, aggregation, water infiltration, and biological activity. The chemical and physical attributes of the soil at 10–20 cm depth are presented in Table 3. For the chemical attributes Al3+, Na+, K+, natural clay, flocculation degree, total sand, and fine sand, no differences were observed among evolutionary stages or between the inner and outer faces of the gullies. The lowest pH values were observed for the outer face, with a difference between the initial and juvenile stages, juvenile and senile stages, and mature and senile stages. For Ca2+ levels, differences between the initial and juvenile stages, initial and mature stages, and initial and senile stages were observed. Among the faces of the gullies, a difference was observed in the mature gully, in which the highest value was observed in the inner face. The largest Mg2+ values were found for the outer face. When evolutionary stages were compared, only differences between the initial and mature stages were observed for initial and senile on both faces, and the highest values for Mg2+ were found in the initial stage. Rev. Ambient. Água vol. 15 n. 2, e2459 - Taubaté 2020 Physical and chemical attributes of soil on … 11 Table 3. Averages of the chemical and physical attributes of the soil initial, juvenile, mature and senile gullies at 0-20 cm depth on the inner (I) and outer (E) faces. pH Ca2+ Mg2+ -1 Stages (cmolc kg ) I E I E I E Initial 4.93aA 4.79abA 0.85bA 0.81abA 1.09aA 1.13aA Juvenile 4.96aA 4.65cB 1.02aA 0.91abA 0.92abA 0.98abA Mature 4.95aA 4.73bcB 1.08aA 0.76bB 0.84bA 0.84bA Senile 4.92aA 4.85aA 1.05aA 0.96aA 0.93bA 0.95bA Al3+ H+Al Na+ -1 Stages (cmolc kg ) I E I E I E Initial 0.96aA 1.35abA 1.99abA 2.64abA 0.010aA 0.010aA Juvenile 0.98aA 1.46aA 2.16aA 3.02aA 0.010aA 0.010aA Mature 0.87aA 1.23abA 1.13bA 2.34bA 0.010aA 0.010aA Senile 1.10aA 1.31aA 2.50aA 3.10aA 0.010aA 0.010aA K+ TOC S Value -1 -1 -1 Stages (cmolc kg ) (g kg ) (cmolc kg ) I E I E I E Initial 0.011aA 0.006aA 5.94bB 8.54cA 1.96aA 1.96aA Juvenile 0.011aA 0.007aA 14.81aA 11.97bcB 1.97aA 1.97aA Mature 0.009aA 0.008aA 11.38abA 16.83abA 1.87aA 1.60bB Senile 0.009aA 0.009aA 14.90aA 17.40aA 2.00aA 1.80abA T Value V Total Clay -1 -1 Stages (cmolc kg ) (%) (g kg ) I E I E I E Initial 3.95aA 4.40abA 40.00abA 43.20aA 285.70abA 278.50bA Juvenile 4.03aA 4.30aA 40.55bA 38.50abA 308.81abA 299.83bcA Mature 2.99bA 3.95bA 37.06aA 40.94abA 233.40bA 297.90bA Senile 4.50aA 4.90aA 55.35bA 44.00aA 355.31aA 348.80aA Natural Clay DF Total sand Stages (g kg-1) (%) (g kg-1) I E I E I E Initial 101.90aA 75.30abA 55.44aA 67.49aA 528.40aA 497.60aA Juvenile 131.65aA 37.00bB 59.75aA 73.64aA 497.80aA 500.60aA Mature 124.81aA 97.20aA 68.57aA 68.52aA 453.70aA 445.00 aA Senile 101.40aA 104.25aA 52.25aA 64.31aA 432.50aA 493.40aA Fine Sand Coarse Sand Silt Stages (g kg-1) I E I E I E Initial 116.70aA 104.70aA 405.50aA 392.90abA 185.90bA 202.80aA Juvenile 107.30aA 124.90aA 380.00abA 378.00aA 197.00bA 199.50aA Mature 99.69aA 101.31aA 350.90abA 343.70bA 190.90bA 186.81aA Senile 90.05aA 104.89aA 341.90bA 338.60abA 334.15aA 208.70aA Equal lowercase letters in the column concern evolutionary stages and equal uppercase letters in the row are inner and outer surfaces, and do not differ by the Kruskal-Wallis test at 5% significance. I: inner face of the gullies; E: outer face of the gullies. The highest values for H + Al and TOC were found in the external face, with differences between the juvenile and mature stages and between the mature and senile stages on both faces; Rev. Ambient. Água vol. 15 n. 2, e2459 - Taubaté 2020 12 João Henrique Gaia Gomes et al. the highest values were associated with senile faces. Higher values for these faces and at this stage may be related to the presence of vegetation, regeneration process, and vegetable residues. Gomide et al. (2011) found a similar pattern as the one described previously in a study on the interior of gullies in the municipality of Lavras in the state of Minas Gerais. They observed a decrease in the organic matter content caused by the removal of vegetation and, consequently, a decrease in fertility. The S value differed between the initial and mature stages and between the juvenile and mature stages on the inner face. Differences were also observed between the faces of mature gullies, with the highest value found in the inner face of the senile stage. For the T value, differences were observed between the initial and mature stages, juvenile and mature stages, and mature and senile stages, with the highest values for both faces of the gully. For V (%), the highest values presented the same pattern as that observed for the T value, differing between the juvenile and mature and between the mature and senile stages on the inner face. Regarding the granulometric fractions of total clay, the highest values were observed in the senile stage. Differences were detected in the inner face, between the mature and senile gullies, and in the outer face, between initial and senile gullies, juvenile and senile gullies, and mature and senile gullies. The higher values of coarse sand, unlike natural clay, were observed in the initial gully, which may be due to the physical barrier formed by the roots preventing the clay fraction from being carried away. Since it is more difficult to remove the coarse sand fraction because of its size, it is carried away later in the process. For this attribute, differences were found between the initial and senile stages on the inner face and between the juvenile and mature stages on the outer face. For the silt fraction, differences were only observed in the inner face, between the initial and senile gullies, juvenile and senile gullies, and mature and senile gullies. The variables Ca2+, Mg2+, Na+, TOC, S value, fine sand, coarse sand, total clay, and natural clay at 10–20 cm depth were not significantly correlated at a cut-off of 5% in the Pearson test. Figure 5 shows the PCA results and Table 4 shows the correlations between the chemical and physical attributes of the soil and axes in the 10–20-cm depth, with a significant correlation at a cut-off of 5% in the Pearson test. Figure 5. PCA for the chemical and physical variables of the soil in the four evolutionary stages and internal and external faces of the gullies in depth of 10-20 cm. Rev. Ambient. Água vol. 15 n. 2, e2459 - Taubaté 2020 Physical and chemical attributes of soil on … 13 Table 4. Values of the correlations between the chemical and physical attributes of the soil and the axes in depth of 10-20 cm in the analyzed stages. Axis Chemical Attributes pH Al3+ H+Al T Value V (%) 1 -0.81 0.85 0.95 0.90 -0.93 2 0.27 -0.17 0.24 0.30 -0.20 Axis Physicists Attributes Total Sand Silt 1 0.53 -0.002 2 -0.58 0.96 We verified that the axes 1 and 2 of the PCA separated the chemical and physical attributes of the soil only between the inner and outer faces of their respective evolutionary stages. The sum of the two axes explained 83.04% of the differences, with axis 1 explaining 60.81% and axis 2 explaining 22.23%. For the SE stage, the most associated variables were H+Al (r = 0.95) and the T value (r = 0.90), which showed a negative correlation with axis 1. The variables most associated with the IE, JE, and ME stages were Al3+ (r = 0.85), which was positively correlated with axis 1, and total sand (r = -0.58), which was negatively correlated with axis 2. For the JI and MI stages, the most associated variable was V (%) (r= -0.93), which showed a negative correlation with axis 1. For stages II and SI, the variables pH (r = -0.81) and silt (r = -0.96) were more associated and had a negative correlation with axes 1 and 2, respectively. Analysis of axes 1 and 2 revealed a separation only between the inner faces of the gullies within different evolutionary stages. In general, the outer face of the gullies is more stabilized than the inner face because erosion caused greater changes in its chemical and physical attributes. When conducting a case study to evaluate the role of vegetation in the stabilization of erosive processes by gullies in a degraded landscape in critical areas of Calhoun, Bastola et al. (2018) verified that environments with pre-established vegetation were more stable. 4. CONCLUSION The chemical and physical attributes of soil react differently in different evolutionary stages and (inner and outer) surfaces at depths of 0–10 cm, and only when the faces are at depths of 10–20 cm, respectively. The stage classified as senile showed the best edaphic conditions for the inner face. 5. REFERENCES ALBUQUERQUE, A. R. da C.; CHATEAUBRIAND, A. D.; PEREIRA, M. C. M.; ROCHA, J. C. F da; NOGUEIRA, L. D.; CARTAXO, E. F. Análise das condições do risco erosivo no entorno do reservatório de Balbina–AM. In: SAFETY, HEALTH AND ENVIRONMENT WORLD CONGRESS, 13., 09-12 Jul. 2013, Vila Real, Portugal. Proceedings[…] Copec, 2013. ALVARES, C. A.; STAPE, J. L.; SENTELHAS, P. C.; GONÇALVES, J. L. de M.; SPAROVEK, G. Köppen’s climate classification map for Brazil. Meteorologische Zeitschrift, v. 22, n. 6 p. 711-728, 2014. https://dx.doi.org/10.1127/0941- 2948/2013/0507 Rev. Ambient. Água vol. 15 n. 2, e2459 - Taubaté 2020 14 João Henrique Gaia Gomes et al. ARTUR, A. G.; OLIVEIRA, D. P.; COSTA, M. C. G.; ROMERO, R. E.; SILVA, M. V. C.; FERREIRA, T. O. Variabilidade espacial dos atributos químicos do solo, associada ao microrrelevo. Revista Brasileira de Engenharia Agrícola e Ambiental, v. 18, p. 141– 149, 2014. https://dx.doi.org/10.1590/S1415-43662014000200003 AUMOND, J. J.; MAÇANEIRO, J. P. de. Abordagem sistêmica e aplicação de rugosidades para desencadear propriedades emergentes em restauração de solos degradados. Ciência Florestal, v. 24, p. 759-764, 2014. https://dx.doi.org/10.5902/1980509815737 AYER, J. E. B.; OLIVETTI, D.; MINCATO, R. L.; SILVA, M. L. N. Erosão hídrica em Latossolos Vermelhos distróficos. Pesquisa Agropecuária Tropical, v. 45, p. 180-191, 2015. https://dx.doi.org/10.1590/1983-40632015v4531197 BASTOLA, S.; DIALYNAS, Y. G.; BRAS, R. L.; NOTO, L. V.; ISTANBULLUOGLU, E. The role of vegetation on gully erosion stabilization at a severely degraded landscape: a case study from Calhoun experimental critical zone observatory. Geomorphology, v. 308, p. 25-39, 2018. https://dx.doi.org/10.1016/j.geomorph.2017.12.032 BOGUNOVIC, I.; PEREIRA, P.; KISIC, I.; SAJKO, K.; SRAKA, M. Tillage management impacts on soil compaction, erosion and crop yield in Stagnosols (Croatia). Catena, v. 160, p. 376-84, 2018. https://dx.doi.org/10.1016/j.catena.2017.10.009 CHEROBIN, S. F. Estimativa de erosão e sua relação com os diferentes mecanismos erosivos atuantes: estudo da voçoroca Vila Alegre. 2012. 115f. Dissertação (Mestrado em Engenharia Ambiental) - Universidade Federal de Ouro Preto, Ouro Preto, 2012. DENG, Y.; XIA, D.; CAI, C.; DING, S. Effects of land uses on soil physic-chemical properties and erodibility in collapsing-gully alluvial fan of Anxi County, China. Journal of Integrative Agriculture, v. 15, p. 1863-1873, 2016. https://dx.doi.org/10.1016/s2095- 3119(15)61223-0 DOBEK, K.; DEMCZUK, P.; RODZIK, J.; HOLUB, B. Types of gullies and conditions of their development in silvicultural loess catchment (Szczebrzeszyn Roztocze region, Poland). Landform Analysis, v. 17, p. 39–42, 2011. FERREIRA, E. de M.; ANDRAUS, M. de P.; CARDOSO, A. A.; COSTA, L. F. dos S.; LÔBO, L. M.; LEANDRO, W. M. Degraded areas recovery, green manure and water quality. Revista Monografias Ambientais, v. 15, p. 228-246, 2016. https://dx.doi.org/10.5902/22361308 GAIA-GOMES, J. H. Caracterização morfométrica da sub-bacia do ribeirão Cachimbal, RJ e atributos edáficos condicionantes no processo erosivo em pedoformas côncava e convexa. 2017. 109f. Dissertação (Mestrado em Engenharia Agrícola e Ambiental) – Universidade Federal Rural do Rio de Janeiro, Seropédica, 2017. GOMIDE, P. H. O.; SILVA, M. L. N.; SOARES, C. R. F. S. Atributos físicos, químicos e biológicos do solo em ambientes de voçorocas no município de Lavras – MG. Revista Brasileira de Ciência do Solo, v. 35, p. 567-577, 2011. https://dx.doi.org/10.1590/s0100-06832011000200026 LAURANCE, W. F.; SAYER, J.; CASSMAN, K. G. Agricultural expansion and its impacts on tropical nature. Trends in Ecology & Evolution, v. 29, p. 107-116, 2014. https://dx.doi.org/10.1016/j.tree.2013.12.001 Rev. Ambient. Água vol. 15 n. 2, e2459 - Taubaté 2020 Physical and chemical attributes of soil on … 15 LIMA, J. S. S.; SOUZA, G. S. de, SILVA, S. de A. Distribuição espacial da matéria orgânica, grau de floculação e argila dispersa em água em área de vegetação natural em regeneração e pastagem. Revista Árvore, v. 37, p. 539-546, 2013. https://dx.doi.org/10.1590/s0100- 67622013000300017 MACHADO, R. L.; RESENDE, A. S. de; CAMPELLO, E. F. C.; OLIVEIRA, J. Á.; FRANCO, A. A. Soil and nutrient losses in erosion gullies at different degrees of restoration. Revista Brasileira de Ciência do Solo, v. 34, p. 945-954, 2010. https://dx.doi.org/10.1590/s0100-06832010000300036 MENEZES, C. E. G.; PEREIRA, M. G.; CORREIA, M. E. F.; ANJOS, L. H. C.; PAULA, R. R.; SOUZA, M. E. de. Litter contribution and decomposition and root biomass production in forests at different successional stages in Pinheiral, RJ. Ciência Florestal, v. 20, p. 439-452, 2010. https://dx.doi.org/10.5902/198050982059 SANTOS, R. D.; LEMOS, R. C. de, SANTOS, H. G. dos.; KER, J. C.; ANJOS, L. H. C. dos; SHIMIZU, S. H. Manual de descrição e coleta de solo no campo. 5. ed. Viçosa: Universidade Federal de Viçosa, 2015. 343p. SANTOS, G. L. dos; PEREIRA, M. G.; LIMA, S. S. de; CEDDIA, M. B.; MENDONÇA, V. M. M.; DELGADO, R. C. Landform curvature and its effect on the spatial variability of soil attributes, Pinheiral-RJ/BR. Cerne, v. 22, p. 431-438, 2016. https://dx.doi.org/10.1590/01047760201622042184 SANTOS, G. L. dos; PEREIRA, M. G.; DELGADO, R. C.; MORAES, L. F. D. de. Padrões da regeneração natural na região de Mar de Morros, Pinheiral-RJ. Floresta e Ambiente, v. 24, p. 1-11, 2017. https://dx.doi.org/10.1590/2179-8087.008115 SCHJONNING, P.; MCBRIDE, R. A.; KELLER, T.; OBOUR, P. B. Predicting soil particle density from clay and soil organic matter contents. Geoderma, v. 296, p. 83-87, 2017. https://dx.doi.org/10.1016/j.geoderma.2016.10.020 SOUSA NETO, E. L. de; ANDRIOLI, I.; ALMEIDA, R. G.; MACEDo, M. C. M.; LAL, R. Physical quality of an Oxisol under an integrated crop-livestock-forest system in the Brazilian Cerrado. Revista Brasileira de Ciência do Solo, v. 38, p.608-618, 2014. https://dx.doi.org/10.1590/S0100-06832014000200025 TEIXEIRA, P. C.; DONAGEMMA, G. K.; FONTANA, A.; TEIXEIRA, W. G. Manual de Métodos de Análise de Solo. 3. ed. Rio de Janeiro: Embrapa Solos, 2017. 264 p. YEOMANS, J. C.; BREMNER, J. M. A rapid and precise method for routine determination of organic carbon in soil. Communications in Soil Science and Plant Analysis, v. 19, p. 1467-1476, 1988. https://dx.doi.org/10.1080/00103628809368027 Rev. Ambient. Água vol. 15 n. 2, e2459 - Taubaté 2020 Ambiente & Água - An Interdisciplinary Journal of Applied Science ISSN 1980-993X – doi:10.4136/1980-993X www.ambi-agua.net E-mail: [email protected] Removal of solids and chemical oxygen demand in poultry litter anaerobic digestion with different inocula ARTICLES doi:10.4136/ambi-agua.2469 Received: 08 Sep. 2019; Accepted: 26 Jan. 2020 Joseane Bortolini1* ; Maria Hermínia Ferreira Tavares2 ; Dayane Taine Freitag3 ; Osvaldo Kuczman2 1Programa de Pós-Graduação em Engenharia Agrícola. Universidade Estadual do Oeste do Paraná (UNIOESTE), Rua Universitária, n° 2069, CEP: 85819-110, Cascavel, PR, Brazil 2Centro de Ciências Exatas e Tecnológicas. Universidade Estadual do Oeste do Paraná (UNIOESTE), Rua Universitária, n° 2069, CEP: 85814-110, Cascavel, PR, Brazil. E-mail: [email protected], [email protected] 3Departamento de Engenharia Agrícola. Universidade Estadual do Oeste do Paraná (UNIOESTE), Rua Universitária, n° 2069, CEP: 85814-110, Cascavel, PR, Brazil. E-mail: [email protected] *Corresponding author. E-mail: [email protected] ABSTRACT Population growth has contributed to increasing poultry production, entailing a high waste loading, mainly poultry litter. One of the alternatives to treat such residues is anaerobic digestion, in which digester startup and generated-digestate quality are related to the material to be digested and to operation conditions, wherein inoculum use is one of the factors. This study therefore aimed to investigate how digestates, such as inocula, influence poultry litter (PL) anaerobic digestion, as well the reduction of solids and chemical oxygen demand (COD). For this, two inocula (bovine and swine digestates) were tested in the digestion process. The inocula were added at loads of 0.67, 1.00 and 1.67 gVS.L-1day-1. A split-plot design was developed and data underwent analysis of variance with means compared by the Tukey's test at 5% significance. Concerning bovine and swine inocula, it was concluded that both are indicated in the process. However, swine inoculum is better indicated because it had a better removal of total solids (TS), volatile solids (VS) and COD. Keywords: biodegradability, bovine inoculum, poultry waste, swine inoculum. Remoção de sólidos e da demanda química de oxigênio na biodigestão anaerobia da cama de aviário com diferentes inóculos RESUMO O crescimento populacional contribuiu para o aumento da produção avícola, o que implica na geração de resíduo de cama de aviário. Uma das alternativas para tratar esses resíduos é a digestão anaeróbia, na qual a partida do digestor e a qualidade do digestato gerado estão relacionadas ao material a ser digerido e às condições de operação, nas quais o uso do inóculo é um dos fatores. Portanto, este estudo teve como objetivo investigar como os inóculos influenciam na digestão anaeróbia da cama de aves, bem como na redução de sólidos e da demanda química de oxigênio (DQO). Para isso, foram testados dois inóculos (bovinos e suínos) no processo de digestão, com cargas de alimentação diárias de 0.67; 1.00 e This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 Joseane Bortolini et al. 1.67 gSV L-1 dia-1. Para a análise estatística foi considerado o delineamento em parcelas subdivididas e os dados foram submetidos à análise de variância com as médias comparadas pelo teste de Tukey com 5% de significância. Em relação aos inóculos de bovinos e suínos, concluiu-se que ambos são indicados ao processo. No entanto, o inóculo suíno é mais indicado porque teve uma melhor remoção de sólidos totais (TS) e DQO. Palavras-chave: biodegradabilidade, inóculo bovino, inóculo suíno, resíduo de aviário. 1. INTRODUCTION The United States of America, Brazil, and China were responsible for the greatest production of poultry meat worldwide in 2017. Among them, Brazil reached a production of 13.3 million tons, with the largest values achieved by the states of Paraná, Santa Catarina and Rio Grande do Sul (ABPA, 2018). Within this background, the broiler industry is responsible for a large consumption of natural resources and, consequently, waste generation, including chicken litter, within an average value of 1,262 kg/(bird year). This value depends on substrate type, season, number of flocks, cycle length and bird density (Rinaldi et al., 2012; Migliavacca and Yanagihara, 2017). Improper disposal of waste may engender large-scale contaminations of land, water, and air (Scherhaufer et al., 2018). Because of this, environmental problems have intensified recently , raising the need for alternatives to minimize impacts and to add value to generated wastes. As the poultry industry has expanded, in addition to producing large quantities of meat, waste production has also increased proportionately (Silveira et al., 2014). Anaerobic treatment of agricultural waste is not only an alternative for energy recovery but also for pollution mitigation (Alice et al., 2014). This technique is well established for renewable energy production and includes waste treatment as an additional benefit. Although anaerobic digestion has proven to be a good tool for degrading several pollutants and organic wastes, it is a complex process and requires monitoring of pH, alkalinity, temperature, volatile fatty acids, organic load, hydraulic retention times, biogas composition, etc. (Mao et al., 2015; Amaral et al., 2014). Sanchez Rubal et al. (2012) determined the influence of temperature, stirring, sludge concentration, and solid retention time (SRT) on biodegradable organic matter acquisition during primary fermentation, clarifying each operational parameter effect on hydrolysis. In addition to biogas production, Orrico Junior et al. (2010) evaluated potential production and quality of biofertilizers derived from anaerobic digestion of pre-composted poultry litter and carcasses. These authors reported sharp reductions in VS contents, on average 44.05%, showing that the process is effective in degrading resistant compounds, such as bird litter. Recent studies have prospected growth medium for microalgae using effluents from poultry litter anaerobic digestion (Singh et al., 2011). Moreover, digestates, widely used as biofertilizers, can also be employed as inoculum in anaerobic digestion, playing a balancing role on microorganism populations at the beginning of this process (Shah et al., 2014). Onofre et al. (2015) have tested the biofertilizer from previous poultry litter anaerobic processes as inoculum, in order to minimize the start of the treatment. Cattle, poultry, and swine biofertilizers may serve as inocula, mainly for difficult to digest materials, because of the high contents of cellulose and lignin, as seen in poultry litter. Costa et al. (2012) investigated such issues and observed that biological co-treatment and thermochemical pretreatments improved poultry litter hydrolysis but led to an accumulation of metabolites, inhibiting methanogenesis. The inoculum source can affect the amount of biogas produced in anaerobic digestion as well as influence the process speed (Swiatczak et al., 2017). Furthermore, several dynamic and microbial factors contribute to the efficiency of organic waste treatment. Rev. Ambient. Água vol. 15 n. 2, e2469 - Taubaté 2020 Removal of solids and chemical oxygen demand … 3 It is worthy to note that different inocula lead to different biogas production, with significant effect of the inoculum on the Biochemical Methane Potential (BMP) (Vrieze et al., 2015). Another paper (Rico et al., 2017) shows the influences of inocula on the anaerobic digestion of pig slurry in UASB reactor. Therefore, this technology must be optimized to reach maximum benefits (Gyenge et al., 2014). Understanding the microbial community and its role in the process is critical to the process control (Shen and Zhu, 2016). Given this background, this study tested two types of inocula, bovine and swine, in the anaerobic digestion of poultry litter, quantifying reductions of solids and COD. 2. MATERIAL AND METHODS 2.1. Substrate and Inocula The substrate consisted of poultry litter gathered from a farm in the city of Quatro Pontes - PR, Brazil. Table 1 shows the characterization of the material with values of hydrogenation potential (pH), total solids (TS), fixed solids (FS), volatile solids (VS), moisture, N and chemical oxygen demand (COD). Prior to biodigestion, residue underwent a pre-treating process with 8 mm mesh sieving to increase its contact surface and facilitate anaerobic digestion. Table 1. Poultry litter and inocula physicochemical characterization. Moisture Material pH TS (%) FS (%) VS (%) N (%) COD (mg.L-1) (%) 7.90 36.00 79.00 1.8 7306.36 Poultry litter 85.00 (±1.10) 12.30 (±0.3) (±0.00) (±1.00) (±1.00) (±0.1) (±50.0) Inocula 7.34 5.44 (±0.05) 2.65 (±0.03) 2.79 (±0.02) - - - Bovine (±0.01) Inocula 7.65 2.46 (±0.02) 1.78 (±0.03) 0.68 (±0.05) - - - Swine (±0.00) As inoculum (IN), two types of fresh material were used: bovine (B) and swine (S), both collected from field biodigesters and kept at room temperature for characterization. The previous table shows the physicochemical characterization of both inocula. 2.2. Poultry litter digestion The trial was carried out at the Laboratory of Bioreactors of the Research Group on Water Resources and Environmental Sanitation of the Western Paraná State University. Two biodigesters built in polyvinyl chloride (0.60 x 0.10 m) were operated. The equipment had an inlet port and a digestate outlet arranged horizontally, with 4 L useful volume, as shown in Figure 1. Figure 1. Experimental module. Rev. Ambient. Água vol. 15 n. 2, e2469 - Taubaté 2020 4 Joseane Bortolini et al. The two biodigesters were inoculated with 30% of their useful volume and 70% with a mixture of water and chicken litter at a ratio of 50 grams of litter for each mixture liter. Twenty- four hours after inoculation, removal of oxygen traces was completed and daily feeding was started, in a semi-continuous flow model, applying loads of 0.67 (L1), 1.00 (L2) and 1.67 (L3) gVS.L-1.day-1, at a concentration of 2% volatile solids. These loads were defined according to previous work (Alcantara et al., 2016). The operating times for each load were 74, 69, and 66 days, respectively, including stabilization time, monitored by the ratios VA/TA (Volatile Acidity/Total Alkalinity) and IA/PA (Intermediate Alkalinity/Partial Alkalinity). The temperature was room temperature, daily monitored. The volume of biogas and methane produced was measured with a Mariotte device filled with sodium hydroxide (NaOH) solution to dissolve carbon dioxide (CO2) (Bertin et al., 2004; Buitrón and Carvajal, 2010; Scoma et al., 2013). However, these results are shown and discussed in another paper. 2.3. Monitoring pH, Ammoniacal Nitrogen and Ratios VA/TA and IA/PA The pH was determined using a benchtop pH meter (Model 3MP) and ammonia nitrogen concentration was monitored following the 4500-NH3 titration method (APHA, 1998). The values for the ratios VA/TA and IA/PA were measured through titration, observing the threshold values reported by Méndes-Acosta et al. (2010) and Ripley et al. (1986). The total alkalinity in anaerobic systems is determined by titration of the sample to pH 4.30, measuring the buffer capacity due to bicarbonate and volatile acids, defined by Ripley et al. (1986) as partial alkalinity (PA) and intermediate alkalinity (IA) respectively. Ripley et al. (1986) established that the ratio IA/PA with values greater than 0.30 indicates the occurrence of disturbances in the process of anaerobic digestion. According to Méndez-Acosta et al. (2010), the VA/TA ratio should be between 0.10 and 0.35, to assure the stability of anaerobic digestion. 2.4. Removal of solids, COD Removal and characterization of digestate and sludge Measurements of TS, FS, and VS were performed based on method 2540 of APHA (2005). In this case, COD quantification was made following method 5220D of APHA (2005). For soluble COD, samples were filtered, using the blank test prepared with distilled water. To determine the micro (Zn, Fe, Cu and Mn) and macronutrients (K, N, Mg, Na, Ca) of the digestate, a nitro-perchloric digestion (3:1) of the samples was performed and an aliquot was taken for reading with atomic absorption equipment. 2.5. Statistics Statistical analyses were performed following a split-plot design, wherein inoculum factor was the main plot (with two levels: B and S). The secondary plot consisted of feeding load factor (with three levels: L1, L2, and L3). The analyses were performed using SISVAR software v. 5.3 (Ferreira, 2010). As response variables, both ratios VA/TA and IA/PA were considered, as well as removal rates of total solids, total volatile solids, total fixed solids, COD total and COD soluble. Data presenting normality by the Kolmogorov-Smirnov's test and homoscedasticity by the Bartlett or Levene's test had the variances submitted to analysis of variance, at 5% significance. Tukey's test was used for mean comparison at a 5% significance level. 3. RESULTS AND DISCUSSION 3.1. Stability through pH, ammonia N, IA/PA ratio e VA/TA ratio With respect to pH, biodigesters remained stable for all treatments, with values near Rev. Ambient. Água vol. 15 n. 2, e2469 - Taubaté 2020 Removal of solids and chemical oxygen demand … 5 neutrality, as shown in Figure 2A. The highest mean values of pH occurred at loads of 1.00 and 1.67 gVS.L-1.day-1, for bovine and swine inocula, respectively. These results corroborate the findings of Onofre et al. (2015), who evaluated the pH of the biofertilizer from poultry litter and pointed out that the pH ranged from 6.6 to 8.0, and determined that the anaerobic digestion process was suited. Although no variations in pH were observed, the presence of ammonia was also monitored throughout the process, and the highest concentration of ammonia (280.51 mg L-1) occurred with a load of 1.67 gVS. L-1 day-1 swine inoculum. According to Chen et al. (2008), ammonia concentrations greater than 1000 mg.L-1 were harmful to the process. Since the presented value is below the concentration threshold reported in the literature, it was concluded that there was no effect of ammonia on anaerobic digestion. Figure 2. Monitoring of the pH, IA/PA ratio and the VA/TA ratio. It should be pointed out that the temporal scale shown in Figure 2A is different from the scales of the other figures because the pH monitoring was registered daily, a fact that did not occur with the monitoring of the ratios VA/TA and IA/PA, solids and COD removals (Figure 2B and 2C). According to Chernicharo (2007), the monitoring of the partial or bicarbonate alkalinity is more useful than the pH monitoring due to scales characteristics: while the pH scale is logarithmic, the scale for alkalinity is linear. It is fundamental to maintain a low concentration of volatile fatty acids and pH in the interval 6.6 to 7.4 (Lahav and Morgan, 2004). Rev. Ambient. Água vol. 15 n. 2, e2469 - Taubaté 2020 6 Joseane Bortolini et al. The main buffer in anaerobic digesters is the ion bicarbonate, at pH from 5.3 to 7.3, -1 expressed in mg of CaCO3 L , varying with the waste type (Lahav and Morgan, 2004). According to Ripley et al. (1986), IA/PA values greater than 0.30 may indicate instability problems in digestion. Here, it was observed that IA/PA values for a load of 0.67 gVS.L-1.day- 1 exceeded 0.30; however, decreasing over time and remaining stable for the other applied loads. Figure 2B denotes that the highest mean values of IA/PA were observed for loads of 1.67 and 0.67 gVS.L-1.day-1, respectively for bovine and swine inocula; however, these values are still below the recommendation of Ripley et al. (1986). Martín-Gonzalez et al. (2013) asserted a possible process stability for values different from 0.3 due to variations in the characteristics of each effluent. Values for the ratio VA/TA were similar for both inocula, presenting slightly higher values in a load of 0.67 gVS.L-1.day-1, as seen in Figure 2C, ranging from 0.252 to 0.228 for bovine and swine inocula, respectively. Table 2 shows the statistical breakdown of VA/TA ratio means. It can be observed that, by fixing the load factor and evaluating its variation in all inoculum levels, a significant difference occurred between loads. The highest values occurred for the loads of 0.67 and 1.67 gVS.L- 1.day-1, considered statistically equal for bovine inoculum. By fixing the inoculum factor, there was no statistically significant difference between loading levels. Table 2. Statistical breakdown of the means of VA/TA ratio as function of inoculum and load. VA/TA Inoculum L1– 0.67 gVS.L-1.day-1 L2 – 1.00 gVS.L-1.day-1 L3 – 1.67 gVS.L-1.day-1 Bovine 0.2523(±0.09) Aa 0.1186(±0.02) Ab 0.1865(±0.04) Aa Swine 0.2286(±0.08) Aa 0.1286(±0.02) Ac 0.1749(±0.04) Ab Means followed by the same uppercase letters within columns (inoculum) and lower case within lines (loads) do not differ from each other by the Tukey's test at 5% significance. The greatest stability time was observed for a load of 1.00 gVS.L-1.day-1; however, at 0.67 gVS.L-1.day-1, the highest means were reached. Nevertheless, these values are within the optimum range for operating levels. The results corroborate those of Kuczman et al. (2011), who evaluated biogas production from cassava wastewater with increasing organic loads and feeding volumes. The microbial adaptation was analyzed by monitoring VA/TA ratio, which remained within a range between 0.14 and 0.30. It is important to note that the operational conditions of the process affect the response of the indicators (Li et al., 2014), indicating the unbalance between acid production and consumption and warning about a possible digestion failure. The temperature mean values were from 16°C to 25°C and values below 20°C occurred only for a load of 1.00 gVS. L-1 day-1, caused by climatic interference. From the mean and standard deviation, the variation in load was 2.1°C and, as reported by Deublein and Steinhauser (2011), methanogenic Archaea are able to change rapidly ideally but the temperature should not vary abruptly by ± 2°C. 3.2. Removal of TS and VS The highest means of TS removal were related to the load 0.67 gVS.L-1.day-1, with swine inoculum (59.46%), as shown in Figure 3A. In addition, bovine inoculum promoted increase in TS removal as loads were raised, with the highest value at the load of 1.67 gVS.L-1.day-1 (57.36%). Rev. Ambient. Água vol. 15 n. 2, e2469 - Taubaté 2020 Removal of solids and chemical oxygen demand … 7 Figure 3. Monitoring of total solid removal and of total volatile solid removal. Table 3 displays the statistical breakdown of the means for TS removal. It is shown that by fixing load factor there was a significant difference as inoculum level increased, with the removal by bovine inoculum statistically equal for 0.67 and 1.00 gVS.L-1.day-1. The greatest value was observed for 1.67 gVS.L-1.day-1 (57.36%). Yet for swine inoculum, loads of 0.67 and 1.00 gVS.L-1.day-1 were statistically similar to each other. On the other hand, loads of 0.67 and 1.67 gVS.L-1.day-1 differed from each other at 5% significance, with the largest removal observed for 0.67 gVS.L-1.day-1 (59.46%). By fixing the inoculum factor, and assessing it according to the loads, there was a significant difference between both inocula at 0.67 gVS.L-1.day-1, being the greatest TS removal for the swine one (59.46%). Table 3. Tukey’s test for means of TS removal at 5% significance. TS removal (%) Inoculum L1 – 0.67 gVS.L-1.day-1 L2 – 1.00 gVS.L-1.day-1 L3 – 1.67 gVS.L-1.day-1 Bovine 44.66(±10.51) Aa 47.65(±6.02) Ba 57.36(±6.39) Bb Swine 59.46(±14.34) Bb 48.30(±4.41) Bba 52.57(±8.60) Ba Means followed by the same uppercase letters within columns (inoculum) and lower case within lines (loads) do not differ from each other by the Tukey's test at 5% significance. The highest VS removal values referred to a load of 1.67 gVS.L-1.day-1 using bovine inoculum, as shown in Figure 3B. Additionally, there was an increase in VS removal as loads increased, with bovine inoculum, being the greatest mean for a load of 1.67 gVS.L-1.day-1 (78.21%). Table 4 displays the statistical breakdown of the means for VS removal. It is shown that by fixing load factor there was significant difference as inoculum level increased, with the greatest removal for bovine inoculum at a load of 1.67 gVS.L-1.day-1 (78.21%). Regarding swine inoculum, loads of 0.67 and 1.00 gVS.L-1.day-1 are statistically equal, as well as 0.67 and 1.67 gVS.L-1.day-1. Conversely, loads of 1.00 and 1.67 gVS.L-1.day-1 differed at the 5% significance from each other, with the greatest removal for swine inoculum at a load of Rev. Ambient. Água vol. 15 n. 2, e2469 - Taubaté 2020 8 Joseane Bortolini et al. 1.67 gVS.L-1.day-1 (71.71%). By fixing the inoculum factor and assessing it according to the loads, there was a significant difference between both inocula at 0.67 and 1.67 gVS.L-1.day-1. The greatest VS removal was found for swine inoculum at 0.67 gVS.L-1.day-1 (67.85%), and for bovine one at 1.67 gVS.L-1.day-1 (78.21%). Table 4. Tukey’s test for means of VS removal at 5% significance. VS removal (%) Inoculum L1 – 0.67 gVS.L-1.day-1 L2 – 1.00 gVS.L-1.day-1 L3 – 1.67 gVS.L-1.day-1 Bovine 50.45(±13.25) Bc 65.07(±10.07) Bb 78.21(±5.38) Aa Swine 67.85(±13.64) Aba 63.82(±9.53) Bb 71.71(±8.54) Ba Means followed by the same uppercase letters within columns (inoculum) and lower case within lines (loads) do not differ from each other by the Tukey's test at 5% significance. The highest removal means, 59.46% (0.67 gVS.L-1.day-1) and 78.21% (1.67 gVS.L-1.day-1), were found for TS and VS, respectively. These findings corroborate Orrico Júnior et al. (2010), who evaluated the technical feasibility of anaerobic digestion of pre-composted poultry litter and carcasses. These authors noted the anaerobic digestion efficiency in degrading resistant compounds, such as chicken litter. Despite the sharp reductions in VS, around 44.05%, this value was lower than that obtained here, evidencing microbial action in the inoculum. This way, the results encountered here are in agreement with those of Silva et al. (2013), who concluded that anaerobic digestion is an efficient procedure to treat organic residues. They also ascertained that biofertilizer addition not only favored system performance regarding pH, but also influenced biogas production and reduced total solids by 40.85%. 3.3. Removal of COD (total and soluble) -1 -1 The major means of CODtotal removal were registered at loads of 0.67 and 1.00 gVS.L .day , using both swine and bovine inocula, respectively, as shown in Figure 4A. Figure 4. Monitoring of total chemical oxygen demand (CODtotal) removal and soluble chemical oxygen demand (CODsoluble) removal. Rev. Ambient. Água vol. 15 n. 2, e2469 - Taubaté 2020 Removal of solids and chemical oxygen demand … 9 As seen in Figure 4B, the load of 1.00 gVS.L-1.day-1 provided the major means of CODsoluble removal. Since data regarding CODtotal removal showed no normality, results did not undergo variance analysis. Table 5 presents the statistical breakdown of means for CODsoluble as a function of inoculum and loads. When load factor is fixed, it is noteworthy seeing a significant difference of loads using bovine inoculum, with the emphasis placed at the load of 1.00 gVS.L-1.day-1, which provided the highest mean (61.31%). For swine inoculum, there was a significant difference among loads, with the highest removal reached by 1.00 gVS.L-1.day-1 (53.29%), being statistically equal at 5% significance for a load of 0.67 gVS.L-1.day-1 (48.91%). When fixing the inoculum factor and evaluating it in relation to the load levels, we could note a statistically significant difference between both inocula at 0.67 and 1.67 gVS.L-1.day-1. -1 -1 COD soluble was effectively removed by using a load of 0.67 gVS.L .day (48.91%) for swine inoculum, and at 1.67 gVS.L-1.day-1 (46.32%) for bovine. The results found in this study are superior to those reported by Blanco et al. (2014), who studied anaerobic digestion of dairy cattle manure with the addition of poultry litter. These authors reported a low COD removal efficiency, on average 36%, which resulted in a low stability for the biofertilizer. Table 5. Tukey’s test for means of COD soluble removal at 5% significance. % COD soluble removal Inoculum L1 – 0.67 gVS.L-1.day-1 L2 – 1.00 gVS.L-1.day-1 L3 – 1.67 gVS.L-1.day-1 Bovine 37.23(±21.07) Bb 61.31(±12.66) Ba 46.32(±14.11) Ab Swine 48.91(±13.75) Ab 53.29(±8.64) Bb 28.48(±15.32) Ba Means followed by the same uppercase letters within columns (inoculum) and lower case within lines (loads) do not differ from each other by the Tukey's test at 5% significance. The results obtained corroborate Lynch et al. (2013), who presented a review detailing advances in the three main alternative disposal routes for poultry litter, which are composting, anaerobic digestion, and direct burning. These authors concluded that such technologies open up opportunities to marketing both energy and nutrients in poultry litter, mainly for anaerobic digestion, once operation conditions are monitored. It is known that the presence of inoculum influences the methanogenic activity and can present significant differences for different inoculum sources (Vrieze et al., 2015; Rico et al., 2017). In this study, it is observed that different types of inoculum may also influence the removal of COD and solids. 3.4. Characterization of digestate and sludge The quality of the digester and its potential for agronomic use depends on many factors. Because of this, each project have to include a specific analysis to determine available nutrient content (Nicoloso et al., 2019). Regarding the values of micronutrients (Zn, Fe, Cu and Mn) in Table 6, note that the highest mean Zn values are for the 1.00 gVS.L-1.day-1 load. Fe values refer to the loads 1.67 gVS.L-1.day-1 and 0.67 gVS.L-1.day-1 for bovine and swine inoculum, respectively. The highest values of Cu refer to the load 1.67 gVS.L-1.day-1, and those of Mn to the load 0.67 0.67 gVS.L-1.day-1 and 1.00 gVS.L-1.day-1, for bovine and swine inoculum respectively. It is observed that the highest mean values of K refer to the loads 0.67 gVS.L-1.day-1 and 1.67 gVS.L-1.day-1 for bovine and swine inocula, respectively. There is a decrease in the concentration of this element with the use of bovine inoculum and increase with swine inoculum in relation to increased loads. Rev. Ambient. Água vol. 15 n. 2, e2469 - Taubaté 2020 10 10 Joseane Bortolini1 et al. Table 6. Characterization of digestate. 1 -1 -1 1 Inoculum Feeding Loads Micronutrients (mg.L ) Mean SD CV (%) Macronutrients (mg.L ) Mean SD1 CV (%) L1 0.67 2.20 ±0.84 38.21 534.60 ±44.60 8.51 Bovine L2 1.00 2.41 ±0.64 26.84 484.70 ±42.70 8.81 L3 1.67 Zn 1.95 ±0.18 9.56 K 478.60 ±17.70 3.69 L1 0.67 2.35 ±0.31 13.19 429.80 ±27.80 6.46 Swine L2 1.00 2.04 ±0.16 7.88 486.24 ±15.50 3.19 L3 1.67 3.36 ±1.07 31.93 528.82 ±10.86 2.05 L1 0.67 4.63 ±0.38 8.27 350.00 ±24.60 7.02 Bovine L2 1.00 3.09 ±1.12 36.23 359.33 ±3.52 0.98 L3 1.67 Fe 5.04 ±0.16 3.27 N 344.87 ±5.70 1.65 L1 0.67 5.64 ±0.33 5.92 356.80 ±67.50 18.91 Swine L2 1.00 4.91 ±1.59 32.50 333.43 ±50.90 5.01 L3 1.67 3.94 ±1.35 38.88 367.30 ±18.37 13.87 L1 0.67 0.31 ±0.11 35.75 75.69 ±5.65 7.46 Bovine L2 1.00 0.27 ±0.06 23.27 54.95 ±13.99 25.47 L3 1.67 Cu 0.35 ±0.07 19.50 Mg 50.84 ±11.03 21.70 L1 0.67 0.47 ±0.11 24.74 103.50 ±12.70 9.24 Swine L2 1.00 0.42 ±0.04 10.93 62.88 ±3.19 5.08 L3 1.67 0.52 ±0.08 15.37 63.78 ±6.97 10.93 L1 0.67 1.38 ±0.21 15.65 316.60 ±23.60 7.45 Bovine L2 1.00 1.33 ±0.12 9.56 231.90 ±25.60 11.02 L3 1.67 Mn 1.17 ±0.17 14.57 139.42 ±7.30 5.24 Na L1 0.67 1.36 ±0.04 3.31 259.82 ±17.23 6.63 Swine L2 1.00 1.38 ±1.05 3.67 217.90 ±21.70 9.98 L3 1.67 1.31 ±0.09 7.00 157.75 ±9.57 6.07 L1 0.67 - - - 387.20 ±40.60 10.49 Bovine L2 1.00 - - - 366.92 ±14.85 4.05 L3 1.67 - - - Ca 305.10 ±60.00 19.66 L1 0.67 - - - 291.80 ±35.50 12.16 Swine L2 1.00 - - - 361.22 ±15.21 4.21 L3 1.67 - - - 386.00 ±35.70 9.24 Rev. Ambient. Água vol. 15 n. 2, e2469 - Taubaté 2020 Removal of solids and chemical oxygen demand … 11 The highest average values of N refer to the loads of 1.00 gVS.L-1.day-1 (359.33 mg.L-1) and 1.67 gVS.L-1.day-1 (367.30 mg.L-1) for bovine and swine inocula, respectively. In addition, the values of K and N are below the values found in effluent from poultry litter digestion by Singh et al. (2002): potassium (1632 mg.L-1) and nitrogen (1570 mg.L-1). The highest average values of Mg and Na refer to the load 0.67 gVS.L-1.day-1, in addition to a decrease in the concentration of these elements with the increased loads. The Ca values refer to the loads of 0.67 gVS.L-1.day-1 and 1.67 gVS.L-1.day-1 for the use of bovine and swine inoculum, respectively. An increase in calcium (Ca) concentration was also observed with increasing charges for swine inoculum. The results presented corroborate with Tessaro et al. (2015), which evaluated the digestion with poultry litter by varying the presence of digestate and water, and concluded that the digestate produced presented assimilable macro and micronutrients by vegetables such as nitrogen, phosphorus, potassium, calcium, magnesium, sodium, iron, boron, copper, zinc and manganese. However, it must be taken into consideration that nutrient loss and segregation processes may occur in the biodigester (Nicoloso et al., 2019). At the end of the experiment, biodigester sludge was quantified, but not presented differences in relation to the volume of sludge generated in the process (1.40 liters), being characterized in relation to nutrients, as presented in Table 7. Table 7. Characterization of sludge the biodigester. Nutrients (mg.L-1) Zn Fe Cu Mn K Mg Na Ca Sludge Bovine 41.98 140.60 12.40 51.70 457.89 328.24 140.49 2815.58 Sludge Swine 43.54 134.11 13.80 13.80 526.69 316.92 151.32 3630.22 The bovine and swine sludge presented very close concentration in relation to the nutrients observed and have a higher concentration of Mn, K and Ca. The use of poultry litter as a digestate is economically desirable, since it represents an internal resource of the rural property. It is a waste that contains a high concentration of nutrients; however, it should be considered that fertilizers with higher proportions of organic nutrients in the organic medium and high lignin and fiber contents have lower decomposition rate in the soil and therefore lower release and availability of nutrients to the plants (Tessaro et al., 2015; Nicoloso et al., 2019). 4. CONCLUSIONS Comparing bovine and swine inocula, it was realized that both could be used in poultry litter digestion because of their stability, as shown by the ratios VA/TA and IA/PA, as well as by the pH values close to neutrality. Relatively to the TS and VS removals efficiencies, the greatest mean values (59.46 and 78.21%, respectively) occurred with the swine inoculum, at the 0.67 gVS.L-1.day-1 load and with the bovine inoculum at the 1.67 gVS.L-1.day-1 load. It was observed that the greatest mean values of CODtotal removals referred to the 0.67 gVS.L-1.day-1 load, with the swine inoculum and 1.00 gVS.L-1.day-1, with the bovine inoculum. Regarding CODsoluble removal, the greatest mean values were reached at the 1.00 gVS.L-1.day-1 load, being 61.31% and 53.29% for bovine and swine inoculum, respectively. It is worth mentioning that the choice inoculum depends on the main purpose process (biogas or biofertilizer production). Therefore, in this case, where the goal was biofertilizer production, the use of swine inoculum is recommended, because it resulted in the best TS and COD removals and higher potassium (K) and calcium (Ca) levels in the generated sludge. Rev. Ambient. Água vol. 15 n. 2, e2469 - Taubaté 2020 12 Joseane Bortolini et al. 5. ACKNOWLEDGEMENTS The authors would like to thank the Graduate Program in Agricultural Engineering of the State University of Western Paraná, to the Coordination for Higher Education Staff Development (CAPES) and to the Araucaria Foundation for granting Master's, Scientific Initiation, and Research Productivity scholarships. 6. REFERENCES ABPA. Annual Report. São Paulo, 2018. 68p. ALCANTARA, M. S.; TAVARES, M. H. F.; GOMES, S. D. Reuse of anaerobic reactor effluent on the treatment of poultry litter. African Journal of Microbiological Research, v. 19, p. 1983-1991, 2016. ALICE, M.; CORIGLIANO, O.; FRAGIACOMO, P. Energetic-Environmental Enhancement of Waste and Agricultural Biomass by Anaerobic Digestion Process. Energy Technology & Policy, v. 1, p. 59-69, 2014. https://doi.org/10.1080/23317000.2014.969452 AMARAL, A. C.; KUNZ, A.; STEINMETZ, R. L. R.; CANTELLI, F.; SCUSSIATO, L. A.; JUSTI, K. C. Swine effluent treatment using anaerobic digestion at different loading rates. Engenharia Agricola, v. 34, n. 3, p. 567-576, 2014. https://doi.org/10.1590/S0100- 69162014000300019 APHA. Standard Methods for the Examination of Water and Wastewater. 20th ed. Washington, 1998. APHA. - Standard Methods for the Examination of Water and Wastewater. 21th ed. Washington, 2005. 1600 p. BERTIN, L.; COLAO, M. C.; RUZZI, M.; FAVA, F. Performances and microbial features of a granular activated carbon packed-bed biofilm reactor capable of an efficient anaerobic digestion of olive mill wastewaters. FEMS Microbiology Ecology, v. 48, n. 3, p. 413– 423, 2004. https://doi.org/10.1016/j.femsec.2004.03.009 BLANCO, M. F. J.; ZENATTI, D. C.; FEIDEN, A.; WEBER, R.; TIETZ, C. M.; GIACOBBO, G. Produção de biogás a partir de dejetos da bovinocultura de leite e cama de aviário. Acta Iguazu, v. 3, n. 1, p. 14-27, 2014. BUITRÓN, G.; CARVAJAL, C. Biohydrogen production from Tequila vinasses in an anaerobic sequencing batch reactor: Effect of initial substrate concentration, temperature and hydraulic retention time. Bioresource Technology, v. 101, p. 9071- 9077, 2010. https://doi.org/10.1016/j.biortech.2010.06.127 CHEN, Y.; CHENG, J. J.; CREAME, K.S. Inhibition of anaerobic digestion process: a review. Bioresource Technology, v. 99, p. 4044-4064, 2008. https://doi.org/10.1016/j.biortech.2007.01.057 CHERNICHARO, C. A. L. Reatores anaeróbios. 2nd ed. Belo Horizonte: DESA; UFMG, 2007. 380 p. COSTA, J. C.; BARBOSA, S. G.; ALVES, M. M.; SOUZA, D. Z. Thermochemical pre and biological co-treatments to improve hydrolysis and methane production from poultry litter. Bioresource Technology, v. 111, n. 2, p. 141-147, 2012. https://doi.org/10.1016/j.biortech.2012.02.047 Rev. Ambient. Água vol. 15 n. 2, e2469 - Taubaté 2020 Removal of solids and chemical oxygen demand … 13 DEUBLEIN, D.; STEINHAUSER, A. Biogas from waste and renewable resources: an introduction. Wiley-VCH, 2011. 578 p. FERREIRA, D. F. SISVAR - Sistema de análise de variância. Versão 5.3. Lavras: UFLA, 2010. GYENGE, L.; RÁDULY, B.; CROGNALE, S.; LÁNYI, S.; ÁBRAHÁM, B. Cultivating conditions optimization of the anaerobic digestion of corn ethanol distillery residuals using response surface methodology. Central European Journal of Chemistry, v. 12, n. 3, p. 868-876, 2014. https://doi.org/10.2478/s11532-014-0542-2 KUCZMAN, O.; GOMES, S. D.; TAVARES, M. H. F.; TORRES, D. G. G.; ALCANTARA, M. S. Specific biogas production from manipueira at one-phase reactor. Engenharia Agricola, v. 31, n. 1, p. 143-149, 2011. http://dx.doi.org/10.1590/S0100- 69162011000100014 LAHAV, O.; MORGAN, B. E. Titration methodologies for monitoring of anaerobic digestion in developing countries – a review. Journal of Chemical Technology and Biotechnology, v. 79, p. 1331-1341, 2004. https://doi.org/10.1002/jctb.1143 LI, L.; HE, Q.; WEI, Y.; HE, Q.; PENG, X. Early warning indicators for monitoring the process failure of anaerobic digestion system of food waste. Bioresource Technology, v. 171, n. 3, p. 491-494, 2014. https://doi.org/10.1016/j.biortech.2014.08.089 LYNCH, D.; HENIHAN, A. M.; BOWEN, B.; MCDONNEL, K. Utilization of poultry litter as an energy feedstock. Biomass and Bioenergy, v. 49, n. 1, p. 197-204, 2013. https://doi.org/10.1016/j.biombioe.2012.12.009 MAO, C.; FENG, Y.; WANG, X. Review on research achievements of biogas from anaerobic digestion. Renewable and Sustainable Energy Reviews, v. 45, n. 2, p. 540-555, 2015. https://doi.org/10.1016/j.rser.2015.02.032 MARTÍN-GONZALEZ, L. M.; FONT, X.; VICENT, T. Alkalinity ratios to identify process imbalances in anaerobic digesters treating source-sorted organic fraction of municipal wastes. Biochemical Engineering Journal, v. 76, n. 1, p. 1-5, 2013. https://doi.org/10.1016/j.bej.2013.03.016 MÉNDEZ-ACOSTA, H. O.; PALACIOS-RUIZ, B.; ALCARAZ-GONZALEZ, V.; GONZALEZ-ALVARAZ, V.; GARCIA-SANDOVAL, J. P. A robust control scheme to improve the stability of anaerobic digestion processes. Journal of Process Control, v. 20, n. 2, p. 375-383, 2010. https://doi.org/10.1016/j.jprocont.2010.01.006 MIGLIAVACCA, A.; YANAGIHARA, JI. Mass Balance Applied to Brazilian Conventional Broiler Houses during One Production Cycle. Brazilian Journal of Poultry Science, v. 19, n. 1, p. 75-86, 2017. https://doi.org/10.1590/1806-9061-2016-0365 NICOLOSO, R. DA S.; BARROS, E. C.; WUADEN, C. R.; PIGOSSO, A. Uso do digestato como fertilizante. In: KUNZ, A.; STEINMETZ, R. L. R.; AMARAL, A. C. do. Fundamentos da digestão anaeróbia, purificação do biogás, uso e tratamento do digestato. Concórdia: Sbera: Embrapa Suínos e Aves, 2019. 209p. ONOFRE, S. B.; ABATTI, D.; REFOSCO, D.; TESSARO, A. A.; ONOFRE, J. A. B.; TESSARO, A. B. Energy potential of poultry litter for the production of biogas. African Journal of Agricultural Research, v. 10, n. 31, p. 3062-3066, 2015. http://dx.doi.org/10.5897/AJAR2015.9932 Rev. Ambient. Água vol. 15 n. 2, e2469 - Taubaté 2020 14 Joseane Bortolini et al. ORRICO JUNIOR, M. A. P.; ORRICO, A. C. A.; LUCAS JUNIOR, J. Biodigestão anaeróbia dos resíduos da produção avícola: cama de frangos e carcaças. Engenharia Agrícola, v. 30, v. 3, p. 546-554, 2010. https://doi.org/10.1590/S0100-69162010000300018 RICO, C.; MONTES, J. A.; RICO, J. L. Evaluation of different types of anaerobic seed sludge for the high rate anaerobic digestion of pig slurry in UASB reactors. Bioresource Technology, v. 238, p. 147-156, 2017. https://doi.org/10.1016/j.biortech.2017.04.014 RINALDI, C. R.; SCHOENHALS, M.; PASSIG, F. H.; FOLLADOR, F. C. Diagnóstico inicial do consumo de insumos e geração de resíduos da avicultura de corte. Engenharia Ambiental, v. 9, n. 3, p. 161-182, 2012. RIPLEY, L. E.; BOYLE, W. C.; CONVERSE, J. C. Improved alkalimetric monitoring for anaerobic digestion of high-strength wastes. Journal of Water Pollution Control Federation, v. 58, n. 5, p. 406-411, 1986. SÁNCHEZ RUBAL, J.; CORTACANS TORRES, J. A.; Del CASTILLO GONZALEZ, I. Influence of Temperature, Agitation, Sludge Concentration and Solids Retention Time on Primary Sludge Fermentation. International Journal of Chemical Engineering, v. 1, n.1, p. 8-12, 2012. https://doi.org/10.1155/2012/861467 SCOMA, A.; BERTIN, L.; FAVA, F. Effect of hydraulic retention time on biohydrogen and volatile fatty acids production during acidogenic digestion of dephenolized olive mill wastewaters. Biomass and Bioenergy, v. 28, p. 51 – 58, 2013. https://doi.org/10.1016/j.biombioe.2012.10.028 SCHERHAUFER, S.; MOATES, G.; HARTIKAINEN, H.; OBERSTEINER, G. Environmental impacts of food waste in Europe. Waste Management, v. 77, n. 1, p. 98- 113, 2018. https://doi.org/10.1016/j.wasman.2018.04.038 SHAH, F. A.; MAHMOOD, Q.; SHAH, M. M.; PERVEZ, A.; ASAD, S. A. Microbial Ecology of Anaerobic Digesters: the Key Players of Anaerobiosis. International Journal of Chemical Engineering, p. 21, 2014. https://doi.org/10.1155/2014/183752 SHEN, J.; ZHU, J. Optimization of methane production in anaerobic co-digestion of poultry litter and wheat straw at different percentages of total solid and volatile solid using a developed response surface model. Journal of Environmental Science and Health, v. 51, n. 2, p. 325-334, 2016. https://doi.org/10.1080/10934529.2015.1109395 SILVA, C. O.; SANTOS, A. S.; SANTOS, M. B.; CEZAR, V. R. S. Anaerobic biodigestion with the substrate formed by a combination of goat manure, cassava wastewater and biofertilizer. Revista Ibero Americana de Ciências Ambientais, v. 4, n. 1, p. 88-103, 2013. SILVEIRA, M. A.; KRETZER, S. G.; NAGAOKA, A. K.; ARROYO, N. A. R.; BAUER, F. C. Production of biogas in downsized digesters stocked with poultry litter. Acta Tecnológica, n. 9, v. 1, p. 9-15, 2014. SINGH, M.; REYNOLDS, D. L.; DAS, K. C. Microalgal system for treatment of effluent from poultry litter anaerobic digestion. Bioresource Technology, v. 102, n. 1, p. 10841– 10848, 2011. https://doi.org/10.1016/j.biortech.2011.09.037 SWIATCZAK, P.; KWIATKOWSKA, A. C.; RUSANOSWSKA, P. Microbiota of anaerobic digesters in a full-scale wastewater treatment plant. Archives of Environmental Protection, v. 43, n. 1, p. 53-60, 2017. https://doi.org/10.1515/aep-2017-0033 Rev. Ambient. Água vol. 15 n. 2, e2469 - Taubaté 2020 Removal of solids and chemical oxygen demand … 15 TESSARO, A. B.; TESSARO, A. A.; CANTÃO, M. P.; MENDES, M. A. Potencial energético da cama de aviário produzida na região sudoeste do Paraná e utilizada como substrato para a produção de biogás. Revista em Agronegócio e Meio Ambiente, v. 8, p. 357- 377, 2015. VRIEZE, J. de; RAPORT, L.; WILLEMS, B.; VERBRUGGE, S.; VOLCKE, E.; MEERS, E.; ANGENENT, L. T.; BOON, N. Inoculum selection influences the biochemical methane potential of agro-industrial substrates. Microbial Biotechnology, v. 8, p. 776-786, 2015. Rev. Ambient. Água vol. 15 n. 2, e2469 - Taubaté 2020 Ambiente & Água - An Interdisciplinary Journal of Applied Science ISSN 1980-993X – doi:10.4136/1980-993X www.ambi-agua.net E-mail: [email protected] Efficiency of horizontal subsurface flow-constructed wetlands considering different support materials and the cultivation positions of plant species ARTICLES doi:10.4136/ambi-agua.2476 Received: 25 Sep. 2019; Accepted: 06 Feb. 2020 Suymara Toledo Miranda1 ; Antonio Teixeira de Matos2* ; Mateus Pimentel Matos3 ; Claudéty Saraiva4 1Departamento de Engenharia Agrícola. Universidade Federal de Viçosa (UFV), Campus Universitário, S/N, CEP: 36570-900, Viçosa, MG, Brazil. E-mail: [email protected] 2Departamento de Engenharia Sanitária e Ambiental. Universidade Federal de Minas Gerais (UFMG), Avenida Pres. Antônio Carlos, n° 6627, CEP: 31270-901, Belo Horizonte, MG, Brazil. 3Departamento de Recursos Hídricos e Saneamento. Universidade Federal de Lavras (UFLA), Avenida Doutor Sylvio Menicucci, S/N, CEP: 37200-000, Lavras, MG, Brazil. E-mail: [email protected] 4Departamento de Pesquisa. Instituto de Laticínios Cândido Tostes. Empresa de Pesquisa Agropecuária de Minas Gerais (EPAMIG), Rua Tenente Luiz de Freitas, n°116, CEP: 36576-000, Juiz de Fora, MG, Brazil. E-mail: [email protected] *Corresponding author. E-mail: [email protected] ABSTRACT The present work evaluated the influence of filling substrate material (crushed PET bottles or fine gravel) on the efficiency of pollutant removal in horizontal subsurface flow constructed wetlands (HSSF-CWs). They were cultivated with a consortium of elephant grass cv. Napier (Pennisetum purpureum Schum) and Tifton 85 (Cynodon spp.) to treat wastewater from a common milk cooling tank (WWMT). For this, six HSSF-CWs were used which had dimensions of 0.6 m tall x 1.0 m wide x 2.5 m long. In order to investigate possible efficiency loss in the removal of pollutants from the system, operation was divided into two periods: Period I (from April to December 2015) and Period II (April to December 2016). Thus, the removal efficiencies of BOD5, solids and total nitrogen (TN), total phosphorus (TP), potassium (K) and sodium (Na) from WWMT were statistically compared. Results indicated that the efficiency of the HSSF-CWs for removing pollutants increased or remained similar after one year and nine months of their operation; and PET bottles were a viable alternative substrate in HSSF-CWs based on the efficient removal of pollutants from WWMT during the one year and nine months of monitoring. Crushed PET bottles constitute a viable substrate for filling HSSF- CWs. Altering the cultivation positions of the plant species did not change pollutant removal efficiencies, but indicates the importance of species arrangement to maximize system performance. Keywords: alternative substrates, plant consortium, wastewater. This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 Suymara Toledo Miranda et al. Eficiência de sistemas alagados construídos de escoamento subsuperficial horizontal considerando diferentes materiais suporte e posição de cultivo das espécies vegetais RESUMO No presente trabalho, avaliou-se a influência do tipo de substrato (garrafas PET amassadas ou brita gnáissica # 0) de preenchimento na eficiência de remoção de poluentes em sistemas alagados construídos de escoamento horizontal subsuperficial (HSSF-CWs) cultivados, de forma consorciada, com capim-elefante cv. Napier (Pennisetum purpureum Schum) e capim- tifton 85 (Cynodon spp.), para o tratamento de água residuária de tanque comunitário de resfriamento de leite (WWMT). Para isso, foram utilizados seis HSSF-CWs, nas dimensões de 0,6 m de altura x 1,0 m de largura x 2,5 m de comprimento. Com o intuito de investigar a possível perda de eficiência na remoção de poluentes pelo sistema, a operação do sistema foi dividida em dois períodos: Período I (de abril a dezembro de 2015) e Período II (abril a dezembro de 2016). Assim, compararam-se estatisticamente, as eficiências na remoção de DBO5, série de sólidos e nitrogênio total (TN), fósforo total (TP), potássio (K) e sódio (Na) da WWMT. Os resultados indicaram que a eficiência dos HSSF-CWs na remoção de poluentes aumentou ou permaneceu semelhante após um ano e nove meses de sua operação e que Garrafas PET amassadas podem constituir alternativa viável de substrato em HSSF-CWs, tendo em vista que propiciaram eficiente remoção de poluentes da WWMT, ao longo de um ano e nove meses de monitoramento. Garrafas PET amassadas são opção viável se substrato para enchimento de HSFF-CWs. Alteração na posição de cultivo das espécies vegetais não alterou as eficiências de remoção de poluentes, mas indicou a importância da forma de arranjo das espécies no desempenho desse sistema. Palavras-chave: água residuária, consórcio de cultivares, substratos alternativos. 1. INTRODUCTION There is an increasing demand for alternative technologies to treat polluted waters and wastewater that require minimal economic resources, both to implement and operate the treatment system. The use of constructed wetlands (CWs) has shown to be a sustainable option, which is why they have been used for decades in the treatment of wastewater (Wang et al., 2017). In treatment with HSSF-CWs, the pollutant removal efficiency varies considerably (Zhang et al., 2014) in function of a complex combination of physical, chemical and biological processes for the removal of contaminants. These are further dependent on many variables, including water application rate, type of wastewater, organic application rate, hydraulic retention time, operating mode (intermittent or continuous), variation of environmental conditions such as temperature, presence and types of vegetation, substrate, biofilm formation and others (Brix, 1997; Kadlec and Wallace, 2009; Ávila et al., 2013). HSSF-CWs that utilize traditional substrate materials, such as gravel, have satisfactory efficiencies for reducing biochemical oxygen demand (BOD5), ranging from 78.5 to 96.3% (Matos et al., 2010). With the use of plastic beads, a high porosity medium (0.8 m³ m-3), Sklarz et al. (2009) obtained an average efficiency of 95%, while Costa et al. (2013) found 69 to 72% when using blast furnace slag as a substrate. On the other hand, traditional filter media often clog quickly due to either the size of their pores or by wear during the operational period (Pedescoll et al., 2009). Thus, the use of materials that are inert and easy to acquire may be an interesting solution in terms of the associated costs (purchase and replacement) (Saraiva et al., 2018). In this context, alternative Rev. Ambient. Água vol. 15 n. 2, e2476 - Taubaté 2020 Efficiency of horizontal subsurface flow-constructed … 3 materials have been evaluated as substrates in different types of systems used for the treatment of wastewater. PET bottles (polyethylene terephthalate), whose disposal has increasingly become an environmental liability, requiring recycling and reuse, have the potential to serve as an alternative support media for HSSF-CWs (Saraiva et al., 2019). Dallas and Ho (2005) studied the efficiency of HSSF-CWs filled with two different substrates: uncrushed PET bottles cut into two or three parts (depending on the size of the bottle) which presented 94% drainable porosity, and gravel which had 40% drainable porosity. According to these authors, in addition to the substrate of cut PET bottles presenting better results in terms of nutrient/pollutant removal, there was a 50% reduction in cost of constructing the HSSF-CWs compared to those filled with gravel. Furthermore, this material is less subject to wear resulting from acid attack in the HSSF-CWs, which permits for longer system operational times without indication of clogging problems in the porous media. Saraiva et al. (2018) observed BOD5 removal efficiencies ranging from 82 to 87% and from 67 to 70% for total solids removal when using crushed PET bottles for the treatment of wastewater from a milk cooling tank (WWMT). Because plant species have different requirements with regards to nutrients and environmental development conditions, intercropping can be another important variable to increase the efficiency of these systems. In order to positively contribute to the performance of the CWs, it is necessary that macrophytes cultivated in these systems have a set of characteristics that include adaptation to the excessively reducing, acidic or alkaline environment, the presence of toxic components, and generally high salinity (Stottmeister et al., 2003). The plants must have a well-developed and deep root system (Cheng et al.; 2003), and thus increase the ability of the HSSF-CWs to remove pollutants (Wu et al., 2005). The root system of plants grown in HSSF-CWs can be stoloniferous or rhizomatous, axial or fasciculated. According to Chen et al. (2007), the rhizomatous root system is generally larger and more superficial and presents greater longevity, while the fasciculate root system is more voluminous, formed by thin roots that grow faster, have larger surface area and greater pollutant removal capacity. According to Chen et al. (2004), plants with fasciculated roots present less tolerance to the anoxic conditions of the medium than those of rhizomatous roots which present a greater capacity for pollutant removal from the waste water being treated in the HSSF-CWs. Because the physiological and productive characteristics of plant species are factors which influence the operational conditions and efficiency of the HSSF-CWs with respect to removal of pollutants, it is important to evaluate reactor performance and influence of plant species with fasciculated and deep root growth, such as elephant grass, and species which propagate by means of stolons and rhizomes, such as Tifton 85 grass. Finally, intercropping should be evaluated, with altering cultivation positions in the HSSF-CWs. Miranda et al. (2019) observed that the sequence of plant species cultivated also influenced the hydrodynamic conditions in HSSF-CWs, which indicates the importance of analyzing the characteristics of the substrate and the effect of pore space expansion by the roots on system pollutant removal efficiency. Little is known about the use of PET bottles as a substrate and the influence of the cultivation position of plant species with different root systems cultivated in consortium on EFFS-CW efficiency. The objective of this study therefore was to evaluate the performance of HSSF-CWs cultivated with elephant grass cv. Napier and Tifton 85 grass in consortium, using crushed PET bottles or fine gravel as a substrate, for the treatment of wastewater from a common milk cooling tank (WWMT). 2. MATERIALS AND METHODS The experiment consisted of six HSSF-CWs, constructed of masonry, with dimensions of 0.6 m tall x 1.0 m wide x 2.5 m long, positioned on the ground with the bottom (level) and sides Rev. Ambient. Água vol. 15 n. 2, e2476 - Taubaté 2020 4 Suymara Toledo Miranda et al. made impermeable with a 0.5 mm thick PVC tarp. They were mounted in parallel and delimited by masonry walls. The units had been in operation since April 2015 for the treatment of wastewater from a common milk tank (WWMT). The HSSF-CWs were filled with gneiss gravel (D60 = 9.1 mm, coefficient of uniformity - CU = D60/D10 = 3.1 and initial porosity, n = 0.398 m³ m-3), and capped and crushed PET bottles (250 and 500 mL) (n = 0.642 m3 m-3). The gravel had an average diameter of 12.5 mm and the crushed PET bottles an average volume of 125 cm3. In the HSSF-CWs filled with capped and crushed PET bottles, a plastic screen (13 mm mesh) was placed on top of the substrate along with a 0.10 m layer of fine gravel in order to prevent PET bottles from floating in the system. The plant species cultivated in the HSSF-CW were elephant grass cv. Napier (Pennisetum purpureum Schum) and Tifton 85 (Cynodon spp.). Each occupied half the surface of these systems in a specific cultivation order as part of the established treatment. In order to investigate possible efficiency loss of pollutants’ removal from the system, the operation was divided into periods: Period I (data generated from April to December 2015 in the experiment conducted by Saraiva et al. (2018)) and Period II (monitoring of the system from March 11, 2016 until December 15, 2016), with the application of WWMT. Each of these phases was performed by a different researcher, with different research objectives. During the two monitoring periods the units were fed continuously for 24 h at the inlet of the HSSF-CW bed. Wastewater generated in the WWMT sanitization process was collected in a 1000 L reservoir, from which it was sent to individual feed containers (200 L volume) of each HSSF- CW (Figure 1a). Influent distribution occurred at a central point at the inlet to each HSSF-CW through a ½ inch plastic tap at which the influent flow was controlled. Depth of the WWMT in all HSSF-CWs was maintained at 0.35 m, providing a nominal or theoretical hydraulic retention time (HRTn) of 3.0 and 1.9 d, respectively, in the HSSF-CWs filled with crushed PET bottles and gneiss gravel. Figure 1b shows the frontal and longitudinal sections of the HSSF-CWs, where it is possible to observe in all sections that the substrate is filled to a depth of 0.45 m. In the HSSF-CW filled with crushed PET bottles, a 0.10 m layer of #3 gneiss gravel was placed on the 0.35 m layer of crushed PET bottles. It should be noted that because the water level was maintained at 0.10 m below the surface of both HSSF-CWs, the liquid height in both systems was 0.35 m. The experimental treatments were as follows: HSSF-CWs filled with the crushed PET bottles substrate, without plant cultivation (CW-P), cultivated in its first half with Tifton 85 grass and in its second half with elephant grass (CW-PTE), and cultivated in its first half with elephant grass and in its second half with Tifton 85 grass (CW-PET); HSSF-CWs filled with the fine gravel substrate, without plant cultivation (CW-B), cultivated in its first half with Tifton 85 grass and in its second half with elephant grass (CW-BTE), and cultivated in its first half with elephant grass and second half with Tifton 85 grass (CW-BET). The experiment was in operation for one year and nine months. Each bed was fed at a flow rate of 0.18 m3 d-1 and a mean organic loading rate (OLR) of -2 -1 33.7 g m d of BOD5, with a hydraulic retention time of 1.90 days in the CWs filled with gravel (CW-B) and 3.10 days in CWs with PET (CW-P). Influent and effluent samples from the HSSF-CWs were collected every 30 days, and a total of eight samples were collected during the system monitoring period from April to December 2016 (Period II). During the experimental period, the aerial portions of the plants were cut 6 times, every 45 days. To understand the variation in efficiency of the systems over time, physical, chemical and biochemical analyses of samples from the influent and effluents were performed in the Laboratory of Water Quality at the Department of Agricultural Engineering of the UFV. The Rev. Ambient. Água vol. 15 n. 2, e2476 - Taubaté 2020 Efficiency of horizontal subsurface flow-constructed … 5 following variables were analyzed: biochemical oxygen demand (BOD5), total solids (TS), total suspended solids (TSS), total nitrogen (TN), total phosphorus (TP), potassium (K) and sodium (Na) according to recommendations and methods of the Standard Methods for the Examination of Water and Wastewater (APHA et al., 2012) and Matos (2015). Figure 1. Schematic design representing an overview of the experiment (a); Frontal section of the HSSF-CWs (A-A’) and cross sections of a HSSF-CW filled with gneiss gravel (B-B’) and the other filled with crushed PET bottles (C-C’) (b). Direct influent and effluent flow measurements were performed weekly, using a stopwatch and graduated cylinder. While conducting the experiment, the water losses by evaporation and evapotranspiration were evaluated. To do this, once a month at one-hour intervals, during 10 hours a day (9:00 a.m. to 7:00 p.m.), the influent and effluent volumes to/from the system were quantified using a 250 mL graduated cylinder. The quantifying evaporation/evapotranspiration is important because of its role in calculating the actual removal efficiencies of pollutants/nutrients, calculated as presented in Equation 1. [(푄퐴푓 .퐶퐴푓) − (푄퐴푓 − 퐸푣) .퐶퐸푓)] 퐸퐹 = (1) (푄퐴푓 .퐶퐴푓) Rev. Ambient. Água vol. 15 n. 2, e2476 - Taubaté 2020 6 Suymara Toledo Miranda et al. Where: EF = Efficiency for removal of the pollutant (%); CAf = inlet concentration -1 (variable unit); QAf = influent flow (m³ d ); CEf = effluent flow (variable unit); Ev = evaporation/evapotranspiration in the HSSF-CWs (m3 d-1). The removal efficiencies of the studied variables were analyzed statistically in a 2 x 3 factorial scheme, for a total of 6 treatments. The first factor, substrate, contained two levels (fine gravel and crushed PET bottles), and the second factor, combination of plants, had three levels (without vegetation - SV, elephant grass followed by Tifton 85 - ET and Tifton 85 followed by elephant grass - TE). The experiment was set up in a randomized complete block design (RCBD), where the number of blocks for each variable was a function of the number of samples. For verification of the assumptions of normality and homogeneity of variance, the Kolmogorov-Smirnov test and the Cochran Bartlett test were applied, respectively. The data that did not meet the normality and homogeneity assumptions was analyzed by non-parametric tests, Kruskal-Wallis for comparison of groupings and that of Wilcoxon for paired data, always at a significance level of 5%. Statistica Version 13.3 was used for data processing and statistical analysis. The means were submitted to Analysis of Variance (ANOVA, p = 0.05), and when significant the Tukey Test (p = 0.05) was applied between the means; when there was a significant interaction between the factors, unfolding was performed. To compare the removal efficiencies between Period I and Period II, the “t” test was used for independent data at 5% significance. 3. RESULTS AND DISCUSSION Table 1 shows the mean values of the surface application rates during experimental monitoring of the systems, Period I (April to December 2015) (Saraiva et al., 2018) and Period II, the period of this study (April to December 2016). As observed, only the surface loading rate of TP differed significantly according to the t-test. Table 1. Mean values of the surface loading rate of organic matter (BOD5), total solids (TS), total nitrogen (TN), total phosphorus (TP), potassium (K) and sodium (Na) applied during the operational periods I (April to December 2015) and II (April to December 2016). Surface loading rates (g m--2 d-1) BOD5 TS TN TP *K Na Period I 32.4 a 42.1 a 1.9 a 0.8 b 0.7 a 0.8 a Period II 33.7 a 47.4 a 2.1 a 0.2 a 0.6 a 0.8 a *T test for the non-parametric data *Means followed by the same lower-case letter, in the column, do not differ according to the t-test at 5% significance. Table 2 presents mean values for the removal efficiencies of BOD5, TS, TSS, TN, TP, K and Na in the HFFV-CWs, during Periods I and II. According to the results presented in Table 2, it was found that there was a significant difference in the removal of BOD5 only in the CW-P (system filled with crushed PET bottles and without plants), where the removal efficiency in Period I (87%) was higher than in Period II (75.0%). However, this result should not be considered, since it is very close to that obtained in other treatments and may be due to the normal variation of this variable. Rev. Ambient. Água vol. 15 n. 2, e2476 - Taubaté 2020 Efficiency of horizontal subsurface flow-constructed … 7 Table 2. Mean removal efficiencies of pollutants/nutrients from the HSSF-CWs during Periods I and II. Period I HSSF-CWs Removal efficiency (%) BOD5 TS TSS TN TP K Na CW-P 87 b 69 a 94 a 21 a 27 a 7 a 6 a CW-PTE 82 a 67 a 91 a 37 a 23 a 16 a -3 a CW-PET 87 a 70 a 96 a 43 a 29 a 23 a 8 a CW-BTE 85 a 52 a 82 a 38 a 22 a 11 a -12 a CW-BET 87 a 57 a 90 a 50 a 27 a 23 a -14 a CW-B 87 a 58 a 91 a 30 a 20 a 15 a 6 a Period II Removal efficiency (%) BOD5 TS TSS TN TP K Na CW-P 75 a 54 a 97 a 30 a 17 a 19 a -5 a CW-PTE 89 a 66 a 95 b 45 a 30 a 23 a -2 a CW-PET 88 a 70 a 98 a 51 b 35 a 38 a 17 a CW-BTE 88 a 63 a 96 b 56 b 38 b 36 a -1 a CW-BET 90 a 54 a 97 a 57 a 39 a 41 a 2 a CW-B 82 a 51 a 96 a 41 a 26 a 26 a -5 a Means followed by the same letter in the column do not differ significantly from each other at 5% significance, according to the t-test. CW P (medium filled with crushed PET bottles, no plants); CW-PTE (medium filled with crushed PET bottles, cultivated in the first half with Tifton 85 grass and in the second half with elephant grass); CW-PET (medium filled with crushed PET bottles, cultivated in the first half with elephant grass and in the second half with Tifton 85 grass); CW-BTE (medium filled with gravel, cultivated in the first half with Tifton 85 grass and in the second half with elephant grass); CW-BET (medium filled with gravel, cultivated in the first half with elephant grass and in the second half with Tifton grass 85); CW-B (medium filled with gravel, no plants). In relation to the TSS only CW-PET and CW-BET differed significantly, where greater efficiencies were obtained in Period II. As the bed matures, there is an increase in retention of larger particles, which could explain the increase from one period to the other, and apparently elephant grass cultivation in the first half of HFFS-CW results in greater SS removal. The TN removal efficiencies differed statistically in the CW-PET and CW-BET, which may have occurred due to the greater stabilization in development and growth of the plants and a microbiota adapted to the WWMT treatment. In both Periods I and II a large variation in the concentration of K and Na in the effluent of the HSSF-CWs was observed; however, there was no statistical differentiation. Results of the statistical analysis for average removal efficiencies of the variables studied during Period II, in relation to the type of support material and the combination of plants in the HSSF-CWs, are presented in Table 3. According to the data presented in Table 3, there was no significant difference in the removal efficiency of BOD5 when comparing the different substrates (crushed PET bottles and gravel). Therefore, it can be inferred that use of the porous medium composed of crushed PET bottles is a viable option based on the high removal of BOD5 that it provides, and the more delayed pore clogging, given the greater porosity of this medium (0.642 m3 m-3) compared to gravel (0.398 m3 m-3). Rev. Ambient. Água vol. 15 n. 2, e2476 - Taubaté 2020 8 Suymara Toledo Miranda et al. Table 3. Mean efficiencies for the removal of BOD5, TS, TSS, TP, TN, K and Na considering the different support materials and combination of plants. *Factor Factor level Removal efficiency (%) BOD5 TS TSS TP Support material GRAVEL 84 a 56 a 97 a 36 b PET 87 a 63 b 97 b 27 a NP 77 a 53 a 97 a 21 a Combination of plants ET 89 b 62 b 98 a 38 b TE 88 b 64 b 96 a 35 b TN K Na Support material GRAVEL 51 b 34 a -1 a PET 42 a 26 a 4 a NP 35 a 22 a 5 a Combination of plants ET 54 b 37 a 13 a TE 51 b 36 a 4 a *Gravel (# 0 gravel), PET (crushed PET bottles), NP (no cultivated plants), ET (cultivated in the first half with elephant grass and in the second half with Tifton 85 grass), TE (cultivated in the first half with Tifton 85 grass and in the second half with elephant grass). *Means followed by the same lower-case letter, per factor, do not differ by the Tukey test at 5% significance. Regarding the cultivation factor, it was observed that the HSSF-CWs differed significantly at 5% significance, i.e.; there was a greater efficiency of BOD5 removal in the cultivated HSSF- CWs than in those with no plants. According to Caselles-Osorio and García (2007), the presence of plants has a significant impact on the removal efficiency of organic material, due to the convective transport of oxygen, or indirectly by evapotranspiration, which increases the fluctuations of water levels and therefore creates a more aerobic environment. Mendonça et al. (2015) evaluated the treatment efficiency of dairy effluents in HSSF-CWs using different substrates (# 0 gravel and a mixture of sand + gravel) and plant species (without vegetation, cattail (Typha latifolia L) and marshland lily (Hedychium coronarium)) and obtained BOD5 removal efficiencies that varied from 79 to 95.2% in cultivated HSSF-CWs and 77.8 to 94.9% in uncultivated HSSF-CWs, but the results were not significantly different. Matos et al. (2012) also verified that there was no significant difference between the cultivated and uncultivated CWs regarding the removal of BOD5. The mean TS removal efficiencies showed significant differences for the two substrates evaluated, but not between the different combinations of plant cultivation. A possible cause of the lower TS removal in the filter media composed of crushed stone may be related to the fact that it is subject to wear over time, releasing solids to the wastewater being treated, which does not occur in the case of the crushed PET bottles. Mean efficiencies of TSS removal did not show significant differences for different substrates and combinations of plant cultivation. In the work conducted by Lee et al. (2004), it was observed that 100% of the TSS removal occurred by physical mechanisms, with no contribution of plants or microbiological mechanisms. Thomas et al. (1995) and Tanner and Sukias (1995) also reported similar removal efficiencies between systems with and without plants, contrary to that found by Karathanasis et al. (2003) who obtained higher TSS removals in a planted unit (88%) compared to an uncultivated CW (46%). Matos et al. (2010) also observed slightly higher mean TSS removal efficiencies in uncultivated HSSF-CWs compared to those obtained in units cultivated with Rev. Ambient. Água vol. 15 n. 2, e2476 - Taubaté 2020 Efficiency of horizontal subsurface flow-constructed … 9 cattail (86%) and Tifton 85 grass (90%). The mean efficiencies of TN removal showed significant differences for different substrates and combinations of plant cultivation in the HSSF-CW beds. According to Wu et al. (2014), different substrates influence establishment of the biofilm and microbial community structure, as well as the treatment efficiency. A porous medium, such as expanded clay, provides a larger surface area for contact with wastewater, favoring biofilm growth. Similar to expanded clay, gravels have larger exposed areas for growth and adherence of microorganisms than beds filled with crushed PET bottles, thus favoring greater TN removal, which primarily occurs by microorganisms (nitrification/denitrification and microbial assimilation). Better performance of cultivated versus non-cultivated HSSF-CWs for N removal may be due to the absorption of this nutrient by plants. In addition, the plant roots provide favorable conditions for the development of microorganisms capable of transforming the chemical forms of nitrogen (Liu et al., 2012). According to Chen et al. (2016), plants release exudates from the roots that affect the density and diversity of the root microbiota, which in turn increase the rates of nutrient removal. Macrophytes provide an increase in nutrient removal from the wastewater under treatment due to their accumulation in the biomass, fixation of inorganic and organic particulates, and if ammonium is present, its transformation into nitrate in the oxidizing rhizosphere (Brix, 1994). Zhang et al. (2016) stated that the presence of plants in CWs can improve the efficiency of wastewater treatment, since they verified that when compared to the control treatment (without plant cultivation), CWs cultivated with M. Aquaticum and A. philoxeroides increased the rates of total nitrogen removal by 50.9% and 36.3%, respectively. The mean efficiencies of TP removal showed significant differences for the different substrates and combinations in plant cultivation, where greater efficiencies of TP removal were obtained in cultivated HSSF-CWs. Amorim et al. (2015) evaluated HSSF-CWs cultivated with Tifton 85 grass for the treatment of swine wastewater and obtained lower efficiency for the removal of TP, which varied between 20 and 30%. Different from the results encountered in the present study, Fia et al. (2017) observed no significant difference in TP removal in cultivated and uncultured CWs. Mendonça et al. (2012) also obtained no significant difference between cultivated and uncultivated HSSF-CWs for the removal of phosphorus, finding mean removal efficiencies of 33.6% (HSSF-CW filled with gravel and cultivated with cattail), 28.8% (HSSF-CW filled with gravel and cultivated with marsh lily), 34.3% (HSSF-CW filled with a mixture of sand + gravel and cultured with cattail), 34.2% (HSSF-CW filled with a mixture of sand + gravel and cultivated with marsh lily) and 18.6% (HSSF-CW filled with a mixture of sand + gravel and without vegetation). There was a greater efficiency of TP removal in HSSF-CWs filled with gravel compared to those filled with crushed PET bottles, which was already expected since crushed PET bottles are, in principle, chemically inert. Mendonça et al. (2012) corroborated with this argument by explaining that phosphorus removal occurs by adsorption processes and that phosphate ions can chemically interact with aluminum or iron present in the gravel used as substrate, thereby increasing the efficiency of TP removal in gravel-filled CWs. Table 3 shows that there was no difference in K removal between cultivated and uncultured HSSF-CWs. Fia et al. (2017) evaluated the influence of vegetation on HSSF-CWs for the removal of pollutants from swine wastewater (SWW). The authors found no significant difference in potassium removal efficiency, with values of 27% in the three HSSF-CWs evaluated (uncultivated, cultivated with cattail and cultivated with Tifton 85 grass). Matos et al. (2010), when treating SWW in uncultivated HSSF-CWs and those cultivated with alternanthera (Alternanthera philoxeroides (Mart.) Griseb.), cattail and Tifton 85 grass, also found no differences in potassium removal; however, efficiencies were higher than those found in the present study (between 29 and 46%). Rev. Ambient. Água vol. 15 n. 2, e2476 - Taubaté 2020 10 Suymara Toledo Miranda et al. It is also observed in Table 3 that there was no difference in Na removal between the cultivated and uncultivated CWs, as well as when considering the different substrates. The average Na removal efficiencies were low, even presenting negative efficiencies. According to Brasil et al. (2005) this can be associated with the great solubility of this chemical element, its low absorption by the plants and its low association with organic material, which is strongly retained by physical processes in the HSSF-CW. In general, the results indicated that nutrient (N, P and K) removal is more associated with the available substrate surface for the development of adhered biofilm than the HRTn of the HFSS-CWs. To increase the surface area of the crushed PET bottles, it is recommended that they have their caps removed and holes drilled in the bottom to allow for flow through the interior, and also biofilm formation on the inner wall. The use of crushed PET bottles as a support medium has shown promising, and that the selection and arrangement of plant species can also provide gain in pollutant-removal efficiency. 4. CONCLUSIONS The pollutant removal efficiency in HSSF-CWs improved or remained similar over one year and nine months of operation, with no difference between the gravel and the capped and crushed PET bottle substrates. HSSF-CWs filled with capped and crushed PET bottles were more efficient in TS and TSS removal than those filled with the gravel substrate; however the gravel substrate provided greater TN and TP removals from WWMT. There were higher mean removal efficiencies of BOD, TS, TP and TN in the cultivated HSSF-CWs when compared to the uncultivated units. Based on the results obtained, the use of PET bottles as a support medium showed to be promising, and that the use of plant species can provide gains in removal efficiency. Cultivation positions of the plant species did not change the pollutant removal efficiencies, but indicates the importance of species arrangement for system performance. 5. ACKNOWLEDGEMENTS To CNPq, for the financial support that allowed for development of this project and for granting the scholarships, EPAMIG, the Federal University of Viçosa and the Department of Agricultural Engineering, for their support and infrastructure. 6. REFERENCES APHA; AWWA; WEF. Standard Methods for the examination of water and wastewater. 22nd ed. Washington, 2012. 1496 p. AMORIM, F.; FIA, R.; SILVA, J. R.; CHAVES, C.; PASQUALIN, P. Unidades combinadas RAFA-SAC para tratamento de água residuária de suinocultura: Parte II Nutrientes. Engenharia Agrícola, v. 35, n. 5, p. 931-940, 2015. https://doi.org/10.1590/1809-4430- Eng.Agric.v35n5p931-940/2015 ÁVILA, C.; REYER, C.; BAYONA, J. M.; GARCÍA, J. Emerging organic contaminant removal depending on primary treatment and operational strategy in horizontal subsurface flow constructed wetlands: Influence of redox. Water Research, v. 47, p. 315-325, 2013. https://doi.org/10.1016/j.watres.2012.10.005 BRASIL, M. S.; MATOS, A. T.; SOARES, A. A.; FERREIRA, P. A. Qualidade do efluente de sistemas alagados construídos, utilizados no tratamento de esgoto doméstico. Revista Brasileira de Engenharia Agrícola e Ambiental, v. 9, p. 133-137, 2005. Rev. Ambient. Água vol. 15 n. 2, e2476 - Taubaté 2020 Efficiency of horizontal subsurface flow-constructed … 11 BRIX, H. Functions of macrophytes in constructed wetlands. Water Science & Technology, v. 29, n. 4, p. 71-78, 1994. https://doi.org/10.2166/wst.1994.0160 BRIX, H. Do macrophytes play a role in constructed treatment wetlands? Water Science and Technology, v. 35, n. 5, p. 11-17, 1997. https://doi.org/10.1016/S0273-1223(97)00047-4 CASELLES-OSORIO, A.; GARCÍA, J. Effect of physic-chemical pretreatment on the removal efficiency of horizontal subsurface-flow constructed wetlands. Environment Pollution, v. 146, p. 55-63, 2007. https://doi.org/10.1016/j.envpol.2006.06.022 CHENG, S. P.; WU, Z. B.; XIA, Y. C. Review on gas exchange and transportation in macrophytes. Acta Hydrobiologica Sinica, v. 27, n. 4, p. 413-417, 2003. CHEN, W.; CHEN, Z.; HE, Q.; WANG, X.; WANG, C.; CHEN, D.; LAI, Z. Root growth of wetland plants with different root types. Acta Hydrobiologica Sinica, v. 27, p. 450-458, 2007. https://doi.org/10.1016/S1872-2032(07)60017-1 CHEN, Z. H.; CHEN, F.; CHENG, X. Y. Research on macrophyte roots in the constructed wetlands (A review). Current Tropic in Plant Biology, v. 5, p. 131-142, 2004. CHEN, Z. J.; TIAN, Y. H.; ZHANG, Y.; SONG, B. R.; LI, H. C.; CHEN, Z. H. Effects of root organic exudates on rhizosphere microbes and nutrient removal in the constructed wetlands. Ecological Engineering, v. 92, p. 243-250, 2016. https://doi.org/10.1016/j.ecoleng.2016.04.001 COSTA, J. F.; PAOLI, A. C.; SEIDL, M.; VON SPERLING, M. Performance and behaviour of planted and unplanted units of a horizontal subsurface flow constructed wetland system treating municipal effluent from a UASB reactor. Water Science and Technology, v. 68, n. 7, p. 1495-1502, 2013. https://doi.org/10.2166/wst.2013.391 DALLAS, S.; HO, G. Subsurface flow reedbeds using alternative media for the treatment of domestic greywater in Monteverde, Costa Rica, Central America. Water Science & Technology, v. 51, n. 10, p. 119-128, 2005. https://doi.org/10.2166/wst.2005.0358 FIA, F. R. L.; MATOS, A. T.; FIA, R.; BORGES, A. C.; CECON, P. R. Efeito da vegetação em sistemas alagados construídos para tratar águas residuárias da suinocultura. Engenharia Sanitária e Ambiental, v. 22, n. 2, p. 303-311, 2017. https://doi.org/10.1590/s1413-41522016123972 KADLEC, R. H.; WALLACE, R. D. Treatment Wetlands. 2. ed. Florida: CRC Press, 2009. 1016 p. KARATHANASIS, A. D.; POTTER, C. L.; COYNE, M. S. Vegetation effects on fecal bacteria, BOD, and suspended solid removal in constructed wetlands treating domestic wastewater. Ecological Engineering, v. 20, n. 157-169, 2003. https://doi.org/10.1016/S0925-8574(03)00011-9 LEE, C. Y.; LEE, C. C.; LEE, F. Y.; TSENG, S. K.; LIAO, C. J. Performance of subsurface flow constructed wetland taking pretreated swine effluent under heavy loads. Bioresource Technology, v. 92, n. 173-179, 2004. https://doi.org/10.1016/j.biortech.2003.08.012 LIU, X.; HUANG, S.; TANG, T.; LIU, X.; SCHOLZ, M. Growth characteristics and nutrient removal capability of plants in subsurface vertical flow constructed wetlands. Ecological Engineering, v. 44, p. 189-198, 2012. https://doi.org/10.1016/j.ecoleng.2012.03.011 Rev. Ambient. Água vol. 15 n. 2, e2476 - Taubaté 2020 12 Suymara Toledo Miranda et al. MATOS, A. T.; FREITAS, W. S.; LO MONACO, P. A. V. Eficiência de sistemas alagados construídos na remoção de poluentes de águas residuárias da suinocultura. Revista Ambiente &Água, v. 5, n. 2, p. 119-132, 2010. https://dx.doi.org/10.4136/ambi- agua.142 MATOS, A. T.; ABRAHÃO, S. S.; LO MONACO, P. A. V. Eficiência de sistemas alagados construídos na remoção de poluentes de águas residuárias de indústria de laticínios. Engenharia Agrícola, v. 32, n. 6, p. 1144-1155, 2012. https://doi.org/10.1590/S0100- 69162012000600016 MATOS, A. T. Manual de análise de resíduos sólidos e águas residuárias. 1. ed. Viçosa: Editora UFV, 2015. 149 p. MENDONÇA, H. V.; RIBEIRO, C. B. M.; BORGES, A. C.; BASTOS, R. R. Remoção de nitrogênio e fósforo de águas residuárias de laticínios por sistemas alagados construídos operando em bateladas. Revista Ambiente & Água, v. 7, n. 2, p. 75-87, 2012. https://doi.org/10.4136/ambi-agua.805 MENDONÇA, H. V.; RIBEIRO, C. B. M.; BORGES, A. C.; BASTOS, R. R. Sistemas alagados construídos em batelada: remoção de demanda bioquímica de oxigênio e regulação de pH no tratamento de efluentes de laticínios. Revista Ambiente &Água, v. 10, n. 2, p. 442- 453, 2015. https://doi.org/10.4136/ambi-agua.1511 MIRANDA, S. T.; MATOS, A. T.; MATOS, M. P.; SARAIVA, C. B.; TEIXEIRA, D. L. Influence of the substrate type and position of plant species on clogging and the hydrodynamics of constructed wetland systems. Journal of Water Process Engineering, v. 31, p. 1-8. 2019. https://doi.org/10.1016/j.jwpe.2019.100871 PEDESCOLL, A.; UGGETTI, E.; LLORENS, E.; GRANÉS, F.; GARCIA, D.; GARCIA, J. Practical method based on saturated hydraulic conductivity used to assess clogging in subsurface flow constructed wetlands. Ecological Engineering, v. 35, n. 8, p. 1216– 1224, 2009. https://doi.org/10.1016/j.ecoleng.2009.03.016 SARAIVA, C. B.; MATOS, A. T.; MATOS, M. P.; MIRANDA, S. T. Influence of substrate and species arrangement of cultivated grasses on the efficiency of horizontal subsurface flow constructed wetlands. Engenharia Agrícola, v. 38, n. 3, p. 417-425, 2018. https://doi.org/10.1590/1809-4430-eng.agric.v38n3p417-425/2018 SARAIVA, C. B.; MATOS, A. T.; MATOS, M. P. D. Extraction capacity of grasses grown in constructed wetland systems using different arrangements and substrates. Engenharia Agrícola, v. 39, n. 5, p. 668-675, 2019. https://doi.org/10.1590/1809-4430- eng.agric.v39n5p668-675/2019 SKLARZ, M. Y.; GROSS, A.; YAKIREVICH, A.; SOARES, M. I. M. A recirculating vertical flow constructed wetland for the treatment of domestic wastewater. Desalination, v. 246, n. 1-3, p. 617-624, 2009. https://doi.org/10.1016/j.desal.2008.09.002 STOTTMEISTER, U.; WIEBNER, A.; KUSCHK, P.; KAPPERLMEYER, U.; KASTNER, M.; BEDERSKI, O.; MÜLLER, R. A.; MOORMANN, H. Effects of plants and microorganisms in constructed wetlands treatments. Biotechnology Advances, v. 22, n. 1-2, p. 93-117, 2003. https://doi.org/10.1016/j.biotechadv.2003.08.010 TANNER, C. T.; SUKIAS, J. P. Accumulation of organic solids in gravel-bed constructed wetlands. Water Science and Technology, v. 32, n. 3, p. 229-239, 1995. https://doi.org/10.1016/0273-1223(95)00624-9 Rev. Ambient. Água vol. 15 n. 2, e2476 - Taubaté 2020 Efficiency of horizontal subsurface flow-constructed … 13 THOMAS, P. R.; GLOVER, P.; KALAROOPAN, T. An evaluation of pollutant removal from secondary treated sewage effluent using a constructed “wetland” system. Water Science Technology, v. 32, n. 3, p.87-93, 1995. https://doi.org/10.1016/0273-1223(95)00608-7 WANG, M.; ZHANG, D. Q.; DONG, J. W.; TAN, S. K. Constructed wetlands for wastewater treatment in cold climate - A review. Journal of Environmental Science, v. 57, p. 293- 311, 2017. https://doi.org/10.1016/j.jes.2016.12.019 WU, J. Q.; RUAN, X. H.; WANG, X. Selection and function of aquatic plants in constructed wetlands. Water Resources Protection, v. 21, n. 1, p. 1-6, 2005. WU, S.; KUSCHK, P.; BRIX, H.; VYMAZAL, J.; DONG, R. Development of constructed wetlands in performance intensifications for wastewater treatment: a nitrogen and organic matter targeted review. Water Research, v. 57, p. 40-55, 2014. https://doi.org/10.1016/j.watres.2014.03.020 ZHANG, D. Q.; JINADASA, K. B. S. N.; GERSBERG, R. M.; LIU, Y.; NG, W. J.; TAN, S. K. Application of constructed wetlands for wastewater treatment in developing countries– a review of recent developments (2000-2013). Journal of Environmental Management, v. 141, p. 116-131, 2014. https://doi.org/10.1016/j.jenvman.2014.03.015 ZHANG, S.; XIAO, R.; LIU, F.; ZHOU, J.; LI, H.; WU, J. Effect of vegetation on nitrogen removal and ammonia volatilization from wetland microcosms. Ecological Engineering, 97, 363-369, 2016. https://doi.org/10.1016/j.ecoleng.2016.10.021 Rev. Ambient. Água vol. 15 n. 2, e2476 - Taubaté 2020 Ambiente & Água - An Interdisciplinary Journal of Applied Science ISSN 1980-993X – doi:10.4136/1980-993X www.ambi-agua.net E-mail: [email protected] Efficiency of electroflocculation in the treatment of water contaminated by organic waste ARTICLES doi:10.4136/ambi-agua.2484 Received: 08 Oct. 2019; Accepted: 26 Jan. 2020 Aline Nunes Andrade1 ; Rodrigo Vieira Blasques1 ; Paulo Cesar Mendes Villis2 ; Darlan Ferreira Silva2* ; Wolia Costa Gomes2 1Universidade Ceuma, Rua Josué Montello, nº 1, CEP: 65075-120, São Luís, MA, Brazil. E-mail: [email protected], [email protected] 2Programa de Pós-graduação em Ciências Ambientais. Mestrado em Meio Ambiente. Universidade Ceuma, Rua Josué Montello, nº 1, CEP: 65075-120, São Luís, MA, Brazil. E-mail: [email protected], [email protected] *Corresponding author. E-mail: [email protected] ABSTRACT Population growth has led to occupation and housing near rivers and lakes. This contributes to the increase of water pollution. The industrial laundry sector, for example, consumes a large quantity for its processes and pollutes water bodies due to the improper disposal of its effluents which contain numerous harmful compounds. This study employed electroflocculation in effluent treatment and evaluated its efficiency by analyzing turbidity, chemical oxygen demand, and pH levels. It used aluminum and zinc plates as sacrificial electrodes and principal component analysis (PCA) as a statistical tool. A maximum electroflocculation time of 40 min was utilized in order to obtain efficient results from the study. The experiment showed significant improvement in the water quality in the physicochemical aspects, primarily concerning the reduction of organic matter in the effluent. The efficiency of this treatment increased with higher current; however, both the aluminum and zinc plates reacted differently to pH, COD, and turbidity. Two principal components were generated to explain 86.90% of the data variance in the experiment. The principal component analysis indicated that the aluminum electrode showed the best correlation (|>0.5|) for pH, COD, and turbidity in the effluent treatment. Keywords: electroflocculation, principal component analysis, water treatment. Eficiência da eletrofloculação no tratamento de águas contaminadas por resíduos orgânicos RESUMO O crescimento populacional levou a ocupações e habitações perto de rios e lagos. Isto contribui para o aumento da poluição da água. O setor de lavanderia industrial, por exemplo, consome alta quantidade de água para seus processos e polui os corpos d'água devido ao descarte inadequado de seus efluentes, que contém inúmeros compostos nocivos. Este estudo utiliza a eletrofloculação no tratamento de efluentes e avalia sua eficiência por meio da análise de turbidez, demanda química de oxigênio (DQO) e níveis de pH. Utilizou chapas de alumínio e zinco como eletrodos de sacrifício e análise de componentes principais (PCA) como This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 Aline Nunes Andrade et al. ferramenta estatística. Foi utilizado um tempo máximo de eletrofloculação de 40 min para obter resultados eficientes do estudo. O experimento mostrou melhora significativa na qualidade da água nos aspectos físico-químicos, principalmente no que diz respeito à redução da matéria orgânica no efluente. A eficiência desse tratamento aumentou com o aumento da corrente, porém, tanto as placas de alumínio quanto as de zinco reagiram de forma diferente ao pH, DQO e turbidez. Dois componentes principais foram gerados para explicar 86,90% da variância dos dados no experimento. A análise dos componentes principais indicou que o eletrodo de alumínio apresentou a melhor correlação (|>0,5|) para pH, DQO e turbidez no tratamento de efluentes. Palavras-chave: análise de componentes principais, eletrofloculação, tratamento de águas. 1. INTRODUCTION Water scarcity is a universal problem that is a result of population growth and lack of adequate sanitation, where a high load of untreated organic, inorganic, and toxic materials is discharged, making this resource unfit for human consumption. The preservation of water resources is a global concern, as wastewater can be reused for water supply. This is practiced in all sectors, including irrigation, industrial, and urban areas (Behling et al., 2019). Human activity, industrial or otherwise, generates waste. Dyes, greases, oils, and other by- products cause various environmental problems, and major contaminations can be linked to oil refineries, chemical industries, textile, pharmaceuticals industries, sewage, agriculture and, household waste. As water scarcity increases, the world depends on developing new technologies for the treatment of toxic organic compounds (Aquino Neto et al., 2011). According to Marques (2017), the lack of piped sewage, poorly constructed wells, and the absence of garbage collection are some of the main problems with basic sanitation in most Brazilian cities. The National Water Resources Policy (NWRP), Law 9.433/1997 (Brasil, 1997), does not regulate effluents, although it ensures the availability of water, manages the rational and integrated use of water resources, creates quality standards for its uses and regulates prevention and defense against critical hydrological events. Article 9 of the NWRP classifies water bodies based on their principal uses and guarantees water quality. It aims to mitigate the costs of pollution control by adopting permanent preventive actions (Bandeira et al., 2018). The greatest challenge of humanity today is providing clean water to the majority of the population on a global scale. There is growing global concern with environment conservation due to rapid population growth, water consumption and quality requirements in various sectors of society, such as industry, which generates highly toxic and non-biodegradable solid and liquid wastes that should be treated (Adams, 2018). Many physical, chemical, and biological methods are used to treat industrial wastewater from laundries; one such method is electrochemical treatment. Proper selection and control of electrodes in the electrochemical system is critical to minimize losses and optimize energy consumption (Ilhan et al., 2008). The electroflocculation technique is one of the simplest and most efficient electrochemical treatments adopted to purify various types of water and industrial effluents. This technique uses simple, easy-to-operate equipment that reduces the amount of sludge. A coagulant is generated by the electrolytic oxidation of a suitable anode, which conducts the material electrically at the appropriate pH to an insoluble metal hydroxide, which is capable of removing a wide range of pollutants (Candito et al., 2012). Electroflocculation uses gas bubbles produced by water electrolysis to remove suspended particles. The process consists of a treatment tank with a cathode and an anode where small Rev. Ambient. Água vol. 15 n. 2, e2484 - Taubaté 2020 Efficiency of electroflocculation in the treatment of … 3 bubbles of hydrogen and oxygen gas are produced by applying an electric current. The electroflocculation process has several advantages over air flotation methods: the bubbles produced are smaller than 1–30 μm diameter, while those produced by scattered air flotation method are 50–100 μm, thus having more surface area and a greater removal efficiency, particularly for finer particles (10 μm) (Mohtashami and Shang, 2019; Kyzas and Matis, 2016). For electroflocculation, the potential applied, the distance between the electrodes, the applied current, the temperature, and the pH are important parameters to be considered. During electroflocculation, oxidation and reduction reactions occur at the anode and cathode, respectively, when a potential is applied to the cell. The greater the distance between the electrodes, the greater the potential applied. (Silva and Silva Neto, 2010). Silva (2005) stated that anodic and cathodic reactions occurred inside the reactor during electroflocculation, which dissociated the water molecules, releasing ions and gases (oxygen and hydrogen) fundamental to the process’s dynamics. In water electrolysis, oxi-reduction reactions occur as follows Equations 1 and 2: − − (−) Cathode: 2H2O (l) + 2e → H2 (g) + 2OH (aq) Ered = −0,83 V (1) + − (+)Anode: 2H2O (l) → O2 (g) + 4H (aq) + 4e Eoxi = −1,23 V (2) The overall reaction is obtained by doubling the cathodic reduction reaction (Equation 1), and adding the anodic oxidation reaction (Equation 2) Equation 3: 2H2O (l) → 2H2(g) + O2(g) (3) The electroflocculation technique is multifactorial, as it considers factors that may influence the process, such as the interaction between constituents of the effluent treated. Such interactions cause difficulty in study and interpretation of the process. Therefore, the use of multivariate statistical analysis is essential, as it provides a better view of each study, which in most cases are not well described by conventional mathematics. Principal component analysis (PCA) is an exploratory method that assists in the elaborating the general hypotheses based on collected data. This technique is capable of separating relevant information from redundant and random information. In PCA, sample grouping defines the structure of the data set through graphs of scores (samples) and loadings (variables), whose axes are the principal components (PCs) on which the data is projected. Considering that one PC is orthogonal to another, it is possible to examine the relationships between samples and variables through scores and loading plots; therefore, the analysis of the set allows us to estimate the influence of each variable in each sample (Ferreira et al., 1999; Haswell and Wamsley, 1998; Sena et al., 2000; Sousa et al., 2019). Thus, a clean and low-cost methodology is essential for the current scenario. Electroflocculation appears as a competitive alternative in wastewater treatment to reduce the Chemical Oxygen Demand (COD). Electrochemical treatment destabilizes the effluent pollutant molecules through an electrical potential applied to the sacrificial electrodes (usually iron (Fe) or aluminum (Al), and consequently, the cations generated react with the colloids of the treated solution floating in the form of hydroxides (Strate, 2014). The present study evaluated the electrolysis duration in effluent treatment using the electroflocculation technique, comparing Al and Zn electrodes for parameters such as temperature, pH, turbidity, and COD, despite their cost during the process. 2. MATERIALS AND METHODS 2.1. Water Sampling and Characterization Water samples were obtained from the Jansen Lagoon in Maranhão state, Brazil. The Rev. Ambient. Água vol. 15 n. 2, e2484 - Taubaté 2020 4 Aline Nunes Andrade et al. experiments were carried out in a custom-built aquarium with a volume of 10200 cm3, with two taps to collect the effluent during the process. The pH was measured by a digital pH meter (Micronal brand) and turbidity was analyzed by the nephelometric method using a bench turbidimeter. For the COD analysis, 5 mL of the sample was pipetted with 2.0 mL of the catalytic solution (H2SO4) and 1.0 mL of the digesting solution (K2Cr2O7) and was placed in a cuvette and then in a digester for two hours at 150°C. Once removed, it was allowed to stand for 10 min. After resting, the cuvette was shaken and the supernatants were removed and read at 620 nm on a spectrophotometer. The samples were analyzed before, during and after the electroflocculation tests. The methodologies for physicochemical characterization, sample preservation, and effluent stabilization time for future analysis were based on the Standard Methods for Examination of Water & Wastewater (APHA et al., 1995). Three experiments were performed to evaluate the effects on the physicochemical variables with varying distances between the electrodes. 2.2. Electroflocculation process The electroflocculation tests were performed using a bench electrolytic reactor and working electrodes: aluminum (130 mm x 70 mm x 3 mm) and zinc (130 mm x 70 mm x 3 mm) positioned above the reactor and connected to a direct current source (Instrutherm brand, Model FA 3030). Two electrodes of the same type were separated with respect to the diameter of a non-conductive material (PVC rings) by varying distances of 0.5; 1.0; 1.5; 2.0; and 3 cm. Figure 1 represents the materials used in the experiments. Figure 1. (A) Aquarium used; (B) Aluminum and zinc plates; (C) Bench reactor; (D) PVC rings. Each electrode was tested for a reaction time of 5, 10, 20, 30, and 40 minutes to analyze if the electroflocculation filtered the water to eliminate the resident organic charge. 2.3. Statistical analysis Statistical analyses were performed using Origin Pro 8 software. Principal Component Analysis (PCA) using Minitab 17 software correlated the variables and treatment time for aluminum and zinc electrodes. The results of the physicochemical analysis displayed the mean and standard deviation (±SD). Analysis of Variance (ANOVA) evaluated the differences between the distances of electrodes, the treatment duration, and the electrodes used in the experiment. A comparative test between the means was performed using the Tukey test (p <0.05). Rev. Ambient. Água vol. 15 n. 2, e2484 - Taubaté 2020 Efficiency of electroflocculation in the treatment of … 5 3. RESULTS AND DISCUSSION The experimental electroflocculation setup for effluent treatment consisted of two aluminum electrodes or two zinc electrodes to evaluate the efficiency of each metal. 3.1. Electroflocculation treatment 3.1.1. Effect of treatment time on effluent pH and temperature The results suggest that varying distances between the electrodes and the treatment time were the two factors that directly affected the process. For the aluminum electrode, a shorter distance between the electrodes (0.5 cm) with longer treatment time (40 min) contributed to an increase in the pH at the end of the process (≈11.5) (Figure 2A). The responses of the zinc electrode treatment were contrary to the aluminum electrode as it resulted in a decrease in effluent pH (≈6.10) (Figure 2B). Kobya et al. (2003) report that changes in pH values vary according to the electrode material used. With the aluminum electrode (Figure 2A), the final pH is higher, caused by the formation of hydroxides due to the dissolution of electrodes while with the zinc electrode (Figure 2B); there is a reduction in pH as there is a decrease in dissolution. The pH tends to remain constant for both electrodes after 30 minutes of electrolysis, which is advantageous as the energy applied to the system decreases. Distance is another factor that directly influences the system’s pH. According to Crespilho and Rezende (2004), the greater the distance between the electrodes, the greater the potential difference that must be applied, since the solution has resistance to the electric current flow. Thus, the characteristics of the effluent combined with the distance between the electrodes may be varied to improve the process’s efficiency. The 2 cm distance for aluminum provided the best results, as it presented a lower pH range and lower electrode wear. For zinc, a distance of 1 cm was more advantageous for the pH range. Figure 2. Experimental pH and temperature data in relation to the distances (0.5, 1, 1.5, 2 and 3 cm) between the electrodes during the electroflocculation process. A and C - using aluminum electrode; B and D - using zinc electrode. Applied potential: 5000 mA. Rev. Ambient. Água vol. 15 n. 2, e2484 - Taubaté 2020 6 Aline Nunes Andrade et al. Temperature has a direct influence on the electroflocculation process. Hydrogen gas microbubbles generated ascended rapidly to the foam layer and accumulated in the upper part of the effluent under treatment (Vieira and Cavalcanti, 2017; Abreu et al., 2019). This effect reduces the passivation of the electrodes and increases process efficiency. With both electrodes, the effluent temperature tended to increase during the process. Cerqueira (2006) states that efficiency can be maintained up to 60°C in the electrolysis process beyond which the efficiency decreases. With the aluminum electrode, the 2 cm distance between the electrodes caused the system temperature to reach approximately 33°C (Figure 2C). With the zinc electrode (Figure 2D), the maximum temperature reached was approximately 18°C, for a 3 cm distance between the electrodes. 3.1.2. Effect of treatment time on turbidity and COD Turbidity may be quantified by analyzing the intensity of light scattered by the sample, which relates the particulate materials to the transparency of the solution (Aquino Neto et al., 2011). The effluent turbidity analysis showed water transparency variations due to the suspension of organic and inorganic materials. Electrolysis increased the concentration of ions and their hydrogen flakes with time. The average turbidity value after 40 min of treatment for aluminum with electrodes 0.5 cm apart was approximately 98.7 to 38.6 NTU (Figure 3A), while the zinc electrode showed no statistical difference (13.60 NTU) (Figure 3B). Figure 3. Experimental turbidity and COD data in relation to the distances (0.5, 1, 1.5, 2 and 3 cm) between the electrodes during the electroflocculation process. A and C - using an aluminum electrode; B and D - using a zinc electrode. Applied potential: 5000 mA.COD analysis studies the quality of dissolved oxygen. It is an important parameter in the characterization of polluted water (Bittencourt et al., 2018). The oxygen demand presented a better response for the shortest distance between the electrodes (0.5 and 1 cm), that is, a lower dissolved oxygen concentration produces the largest amount of reduced organic matter, thus increasing the efficiency of effluent treatment. The mean values ranged from 779.4 to 504.2 mg L-1 (Figure 3C) for treatment with the aluminum electrodes, and from 179.0 to 160.0 mg L-1 (Figure 3D) with the zinc electrodes. Rev. Ambient. Água vol. 15 n. 2, e2484 - Taubaté 2020 Efficiency of electroflocculation in the treatment of … 7 3.2. Principal Component Analysis The multivariate analysis technique reduces a data matrix to fewer manageable variables, called principal components (PCs), where the first PCs contain the maximum variability (information) of the analyzed data set. The relationship between the samples and variables can be visualized and interpreted by a score and a loading plotting from the PCA (Karki et al., 2017; Higgins et al., 2019; Hajigholizadeh and Melesse, 2017). The PCA was performed to evaluate the correlations between all the studied variables. From the results of PCA, principal component 1 (PC1) is most significant in describing the statistical model, explaining 57.70% of the total data variation using aluminum and zinc electrodes. The first two dimensions of the PCA explains 86.90% of the variance. Four clusters, three related to experiments performed with the aluminum electrode and one to the zinc electrode, were the highlights. The treatment using the aluminum electrode was the most efficient in terms of lower pH, turbidity, COD, and temperature. Figure 4 shows the PCA for treatment duration and the parameters evaluated during the electroflocculation process using aluminum and zinc electrodes. Figure 4. Principal component analysis (PCA) for treatment times and parameters evaluated during the electroflocculation process using aluminum and zinc electrodes. T-0 (zero); T-5 (five minutes); T-10 (ten minutes); T- 20 (twenty minutes); T-30 (thirty minutes) and T-40 (forty minutes). Al (aluminum electrode); Zn (zinc electrode). Figure 4 shows that treatment durations of 20, 30, and 40 min increased correlation among the variable’s pH, turbidity, COD, and temperature for aluminum electrode during electroflocculation. For the zinc electrode, there was no positive correlation with any of the evaluated parameters. The experimental data obtained was smaller than the aluminum electrode’s data; thus, there was a lower pH range, turbidity, COD, and temperature. Table 1 shows the correlation coefficients of the first two principal components for the evaluated parameters. From Table 1, it can be seen that the two principal components (PCs 1-2) were sufficient to describe the model, and together they account for 86.90% of the cumulative variance. Most information regarding the system (86.90% of the variation) was revealed by CP1 (57.70%) and CP2 (29.20%). Values highlighted in bold were considered significant in the mathematical model, where temperature and COD were the dominant variables in CP1 and temperature and pH in CP2. Rev. Ambient. Água vol. 15 n. 2, e2484 - Taubaté 2020 8 Aline Nunes Andrade et al. Table 1. Loadings of the variables for the first two principal components. Variables PC1 PC2 Temperature 0.508850 -0.542761 Turbidity 0.495557 0.420871 pH 0.391010 0.652436 COD 0.585325 -0.320320 Eigenvalues 2.3080 1.1699 Total variance (%) 57.70 29.20 Cumulative variance (%) 57.70 86.90 *Bold values indicate significant correlation (|>0,5|). COD (Chemical Oxygen Demand). PC1 (Principal component 1); PC2 (Principal component 2). 4. CONCLUSIONS This study evaluated the electrolysis duration in effluent treatment using the electroflocculation technique, comparing aluminum and zinc electrodes for parameters such as temperature, pH, turbidity, and COD. The efficiency of the effluent treatment by electroflocculation varied with the duration, the distance between the electrodes, and the type of electrode used; however, it was efficient and viable as it reduced organic and inorganic residues, which was evaluated indirectly by COD. The parameters with the best correlation to the process were turbidity, COD, and pH. The efficiency of removing pollutants from aluminum and zinc electrodes was best for the shortest distance between plates (0.5 and 1 cm) and a 40 min duration of electroflocculation, and presented better values for temperature, turbidity, and COD. The electrochemical process is more efficient than traditional techniques in removing colloidal particles in suspension, organic matter, and metals, by generating a coagulant inside the reactor (“in situ”) and the combined action of microbubbles generated by cathode. Its advantages include versatility, energy efficiency, speed in smaller systems, simplicity of apparatus used, and non-use of chemical and biological reagents for wastewater treatment. 5. REFERENCES ABREU, J. D.; ADAM, C.; COSTA, A. F.; MARIAN, S.; KOSLOWSKI, L. A. D. Tratamento de efluente proveniente de serigrafia via eletrocoagulação. Brazilian Journal of Animal and Environmental Research, v. 2, n. 1, p. 547-556, 2019. ADAMS, E. A. Intra-urban inequalities in water access among households in Malawi's informal settlements: Toward pro-poor urban water policies in Africa. Environmental Development, v. 26, n. 42, 2018. https://doi.org/10.1016/j.envdev.2018.03.004 APHA; AWWA; WEF. Standard Methods for the Examination of Water and Wastewater. 19. ed. Washington, 1995. AQUINO NETO, S.; MAGRI, T. C.; DA SILVA, G. M.; DE ANDRADE, A. R. Tratamento de resíduos de corante por eletrofloculação: um experimento para cursos de graduação em química. Química Nova, v. 34, n. 8, p. 1468–1471, 2011. BANDEIRA, A. A.; ESQUERRE, K. R.; BORGES, R. B. A regulamentação sobre o tratamento e a disposição final de efluentes industriais: avaliação do gerenciamento de efluentes no Polo Industrial de Camaçari – Estado da Bahia. Revista Direito Ambiental e sociedade, p. 121-148, 2018. Rev. Ambient. Água vol. 15 n. 2, e2484 - Taubaté 2020 Efficiency of electroflocculation in the treatment of … 9 BEHLING, L.; PAVÃO, D. B.; ALVES, A. A. A.; SANTOS, B. L. B.; TONES, A. R. M. Eletrofloculação aplicada no tratamento de efluente lácteo: delineamento experimental e otimização de múltiplas respostas. In: SIMPÓSIO INTERNACIONAL DE QUALIDADE AMBIENTAL, 11., 02-04 out. 2018, Porto Alegre. Anais[...] Porto Alegre: ABES, 2019. p. 3-13. BITTENCOURT, L. A.; LIMA, A. A.; SCHLINDWEIN, C.; BANCZEK, E. P.; FURSTENBERGER, C. B. Tratamento do efluente do biodiesel utilizando a técnica de eletrofloculação com diferentes eletrodos. Brazilian Journal of Animal and Environmental Research, v. 1, n. 1, p. 253-266, 2018. BRASIL. Presidência da República. Lei n. 9.433, de 9 de janeiro de 1997. Institui a Política Nacional de Recursos Hídricos, cria o Sistema Nacional de Gerenciamento de Recursos Hídricos, regulamenta o inciso XIX do art. 21 da Constituição Federal, e altera o art. 1º da Lei nº 8.001, de 13 de março de 1990, que modificou a Lei nº 7.990, de 28 de dezembro de 1989. Diário Oficial [da] União: seção 1, Brasília, DF, 09 jan. 1997. CANDITO, L. C.; GOMES, J. A. C. P.; JAMBO, H. C. M. Desenvolvimento de reator eletroquímico para a oxidação de compostos de amônia em águas residuais de refinarias de petróleo. In: PAINEL PEMM, 2012, Rio de Janeiro. Trabalhos[...] Rio de Janeiro: UFRJ, 2012. CERQUEIRA, A. A. Aplicação da técnica de eletrofloculação no tratamento de efluentes têxteis. 2006. 111f. Dissertação (Mestrado) - Universidade do Estado do Rio de Janeiro, Rio de Janeiro, 2006. CRESPILHO, F. N.; REZENDE, M. O. O. Eletroflotação: princípios e aplicações. São Carlos: Rima, 2004. 96 p. FERREIRA, M. M. C.; ANTUNES, A. M.; MELGO, M. S.; VOLPE, P. L. O. Quimiometria I: calibração multivariada, um tutorial. Química Nova, v. 22, p. 724-731, 1999. HAJI GHOLIZADEH, M.; MELESSE, A. M. Assortment and spatiotemporal analysis of surface water quality using cluster and discriminant analyses. Catena, v. 151, p. 247-258, 2017. https://doi.org/10.1016/j.catena.2016.12.018 HASWELL, S., J.; WALMSLEY, A. D. Multivariate data visualization methods based on multi-elemental analysis of wines and coffees using total reflection X-ray fluorescence analysis. Journal of Analytical Atomic Spectrometry, v. 13, p. 131-134, 1998. https://doi.org/10.1039/A705317G HIGGINS, V.; HOOSHMAND, S.; ADELI, K. Principal component and correlation analysis of biochemical and endocrine markers in healthy pediatric population (CALIPAPER), Clinical Biochemistry, v. 66, p. 29-36, 2019. https://doi.org/10.1016/j.clinbiochem.2019.02.004 ILHAN, F.; KURT, U.; APAYDIN, O.; GONULLU, M. T. Treatment of leachate by electrocoagulation using aluminum and iron electrodes. Journal of Hazardous Materials, v. 154, p. 381–389, 2008. https://doi.org/10.1016/j.jhazmat.2007.10.035 KARKI, V.; AGARWAL, R.; ALAMELU, D. Determination of spatial distribution of alloying and impurity elements in zircaloy using imaging secondary ion mass spectrometry and principal component analysis, Vacuum, v. 136, p. 1-9, 2017. https://doi.org/10.1016/j.vacuum.2016.11.015 Rev. Ambient. Água vol. 15 n. 2, e2484 - Taubaté 2020 10 Aline Nunes Andrade et al. KYSAS, G. Z.; MATIS, K. A. Electroflotation process: A review. Journal of Molecular Liquids, v. 220, p.657-664, 2016. http://dx.doi.org/10.1016/j.molliq.2016.04.128 KOBYA, M.; CAN, O. T.; BAYRAMOGLU, M., Treatment of textile wastewater by electrocoagulation using iron and aluminum electrodes, Journal of Hazardous Materials, B100, p. 163-178, 2003. http://dx.doi.org/10.1016/S0304-3894(03)00102-X MARQUES, M. B. L. Construção de jardim filtrante (wetlands) como alternativa de tratamento de água cinza em uma propriedade rural do município de Ilha Solteira - SP. 2017. 56f. Trabalho de Conclusão de Curso (Graduação em Ciências Biológicas) - Universidade Estadual Paulista, Ilha Solteira, São Paulo. 2017. MOHTASHAMI, R.; SHANG, J. Q. Treatment of automotive paint wastewater in continuous- flow electroflotation reactor. Journal of Cleaner Production, v. 218, p. 335-346, 2019. https://doi.org/10.1016/j.jclepro.2019.01.326 SENA M. M.; POPPI, R. J.; FRIGHETTO, R. T. S.; VALARINI, P. J. Avaliação do uso de métodos quimiométricos em análise de solos. Quimica Nova, v. 23, p. 547-556, 2000. SILVA, P. C. F. Tratamento de Resíduos Líquidos Industriais pelo Processo Eletrolítico: Uma Alternativa para Gerenciamento dos Resíduos Líquidos Gerados nas Indústrias Mecânicas Fabricantes de Equipamentos para Produção de Petróleo. 2005. 96f. Dissertação (Mestrado) – Universidade Federal Fluminense, Niterói, 2005. SILVA, J. S.; SILVA NETO, A. C. Tratamento da água do petróleo por eletrocoagulação/eletrofloculação. Revista Ambientale, v. 2, p. 104-116, 2010. STRATE, J. Otimização de um sistema de eletrofloculação em fluxo contínuo para o tratamento de efluentes líquidos das indústrias de laticínios. 2014. 83f. Trabalho de Conclusão de Curso (Graduação) - Centro Universitário Univates, Lajeado, 2014. SOUSA, D. G.; MARQUES, D. S.; SANTOS, V. S.; SOUSA, A. C.; FIGUEIREDO, G. A. Aplicação da técnica de análise exploratória no monitoramento da qualidade do rio Cuiá, João Pessoa-PB. Ambiência, v. 15, p. 131-145, 2019. VIEIRA, S. P.; CAVALCANTI, A. P. Obtenção de novos materiais a partir as águas residuais da produção de biodiesel tratadas por eletrofloculação. Revista CIATEC-UFP, v. 9, n. 2, p. 28-36, 2017. Rev. Ambient. Água vol. 15 n. 2, e2484 - Taubaté 2020 Ambiente & Água - An Interdisciplinary Journal of Applied Science ISSN 1980-993X – doi:10.4136/1980-993X www.ambi-agua.net E-mail: [email protected] Membrane bioreactor for mall wastewater treatment ARTICLES doi:10.4136/ambi-agua.2489 Received: 01 Nov. 2019; Accepted: 06 Feb. 2020 Everton Luis Butzen1 ; Gabriel Capellari Santos1 ; Sandrini Slongo Fortuna1 ; Vandré Barbosa Brião2* 1Faculdade de Engenharia e Arquitetura. Programa de Pós Graduação em Engenharia Civil e Ambiental. Universidade de Passo Fundo (UPF), Rodovia BR 285, S/N, CEP: 99052-900, Passo Fundo, RS, Brazil. E-mail: [email protected], [email protected], [email protected] 2Faculdade de Engenharia e Arquitetura. Universidade de Passo Fundo (UPF), Rodovia BR 285, km 292, n° 7, CEP: 99052-900, Passo Fundo, RS, Brazil *Corresponding author. E-mail: [email protected] ABSTRACT Malls concentrate a large number of people in a relatively small area, and thus generate concentrated urban wastewater. This study evaluated the performance of a membrane bioreactor (MBR) as an alternative for the treatment of mall wastewater. Wastewater samples without any previous treatment were collected from a medium-size mall and showed a high chemical oxygen demand (COD) near 2,000 mg L-1. The MBR operated with a constant pressure of 40 kPa during 60 days with a sludge age of 30 days. Concentration of biomass was 3,738±930 mg L-1 and average permeate flux was 7.0 L h-1 m-2. The MBR was able to remove 91.2% and 97.2% of color and turbidity, respectively. Furthermore, COD removal was approximately 90% and biochemical oxygen demand (BOD) 88%. In addition, the MBR produced a phosphorus removal near 50%, and for nitrogen, 80%. The MBR system proved to be an efficient process for the removal of the pollutants, remaining stable even with the oscillation of the characteristics of the raw sewage, presenting great potential for application in the treatment of sewage from malls and effluents with high organic loads. Keywords: activated sludge, effluent, MBR, sewage, ultrafiltration. Bioreator de membrana para o tratamento de águas residuais de shopping centers RESUMO Os shoppings têm um alto movimento de pessoas em locais compactos e, assim, geram águas residuais urbanas concentradas. Este estudo avaliou o desempenho do biorreator de membrana (MBR) como uma alternativa para o tratamento de águas residuais de shopping centers. Amostras de águas residuais sem tratamento prévio foram coletadas em um shopping de tamanho médio e apresentaram alta demanda química de oxigênio (DQO) próxima a 2.000 mg L-1. O MBR operou com pressão constante de 40 kPa durante 60 dias com idade do lodo de 30 dias. A concentração de biomassa foi de 3.738 ± 930 mg L-1 e o fluxo médio de permeado foi de 7,0 L h-1 m-2. A MBR conseguiu remover 91,2% e 97,2% da cor e turbidez, respectivamente. Além disso, a DQO foi removida em aproximadamente 90% e a demanda bioquímica de oxigênio (DBO) em 88%. Além disso, o MBR produziu uma remoção de fósforo This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 Everton Luis Butzen et al. perto de 50% e para o nitrogênio esse valor foi de 80%. O sistema MBR demonstrou ser um processo eficiente na remoção dos poluentes mantendo-se estável mesmo com a oscilação das características do esgoto bruto, apresentando grande potencial de aplicação no tratamento de esgoto de shopping centers e efluentes com altas cargas orgânicas. Palavras-chave: efluente, esgoto, lodo ativado, MBR, ultrafiltração. 1. INTRODUCTION Malls are densely occupied urban structures. Their infrastructure includes water supply, sanitation and storm drainage, and thus generates effluents (e.g. from toilets and restaurants) with higher organic load than domestic wastewater. The compactness of malls makes the treatment of sewage difficult, since in general this treatment occupies large areas located in the middle of cities, lacking efficient solutions for an adequate environmental balance. The treatment of sewage from malls can create a bottleneck in the mall’s operation. The increase of sewage generation has been overloading existing municipal sewage treatment plants, and in many cases there is no room available for plant expansion (Neoh et al., 2016). Restrictions of physical space for new systems or expansion of existing systems, the low performance of conventional systems, the impossibility of interconnections in the collection networks and overloads in the treatment plants can make it difficult to treat mall sewage. In addition to containing pathogens, microorganisms and toxic wastes, raw sewage may contain high concentrations of nitrogen and phosphorus, and discharges without proper treatment may enhance water eutrophication (Belli et al., 2014). Activated sludge is a usual process for the treatment of sewage and can be useful for treatment of mall wastewater because it can remove high organic load and nitrogen and can reduce the risk of pathogens in the effluent. However, these treatments can require a large physical space and have high operating costs. Furthermore, secondary settling has limitations. It can present low efficiency and sedimentation problems when hydraulic detention time is low; there can be small biological flakes with open structures or malformation, and the occurrence of sludge bulking can also lead to poor operation (Subtil et al., 2013). The result is a treated effluent with suspended and colloidal material, increasing BOD and suspended solids due to cellular material in the water. Membrane bioreactors (MBR) combine the activated sludge process with solid/liquid separation through membranes, replacing the sedimentation stage of conventional systems (Rodríguez-Hernández et al., 2014). MBRs show a great advance in wastewater treatment. In addition, the effluent treatment is considered to be superior to conventional biological systems as it produces a better quality permeate (Komesli et al., 2015). The main characteristics of the MBR are the large capacity of retention of biological material in the membranes, operation with large biomass load with longer cell detention time, and the removal of bacteria and viruses without the incorporation of chemical agents (Villain and Marrot, 2013; Komesli et al., 2015, Maqbool et al., 2014). They are flexible and compact systems that require little area for installation, and they have been applied on a large scale worldwide and have been constantly optimized and adapted to new configurations that seek to improve their performance (Huang and Lee, 2015). Membrane bioreactors can be easily adapted to different operating cycles, with the incorporation of anaerobic / anoxic periods, which can operate with high efficiency in the removal of organic matter and nutrients with simultaneous nitrification and denitrification conditions (Barbosa et al., 2016; Belli et al., 2014; Capodici et al., 2015). The process with MBR has been researched for the treatment of effluents in several sectors: Rev. Ambient. Água vol. 15 n. 2, e2489 - Taubaté 2020 Membrane bioreactor for mall wastewater treatment 3 Keskes et al. (2012) used MBR for the wastewater of slaughterhouse effluent; Belli et al. (2014) and Capodici et al. (2015) treated municipal wastewater; and Nguyen et al. (2016) for wastewater from hospitals. Praneeth et al. (2014) used a submerged MBR for treatment of dairy wastewater. Subtil et al. (2014) compared two configurations of MBR for the treatment of domestic wastewater. However, malls can generate high volumes of wastewater in restricted areas. Thus, there is a need to evolve the study to evaluate the real capacity of MBR to be applied in the malls. Furthermore, the stability of the systems and the determination of optimal operating conditions with the control of membrane clogging remain major challenges for MBRs (Krzeminski et al., 2017), and studies should be expanded to increase knowledge on the subject. This study evaluated the feasibility of the membrane bioreactor system for the treatment of mall effluent, analyzing physical and chemical parameters of the raw sewage and permeate, treatment efficiency and their stability. 2. MATERIAL AND METHODS The mall where the samples of the wastewater were collected is located at University of Passo Fundo (Brazil). The mall houses different commercial establishments, such as a drug store, bookstore, bank branch, toilets, as well as a food court with seven restaurants, snack bars, ice cream shop and coffee shop. The sampling was carried out in the sewer drain (GPS position: -28.232340, -52.382619) located near the building, without any preliminary treatment, over a period of 60 days between August and September. The characterization of the wastewater is shown in Table 1. Table 1. Physic chemical characteristics of the mall sewage and permeate, and the removal efficiency of MBR during a 60-day treatment period. Parameter Raw wastewater Permeate Removal Color (Hazen) 580.10±280.27 51.05±11.08 91.20% Turbidity (NTU) 680.10±336.01 19.00±9.72 97.20% COD (mg L-1) 1.849.90 ± 174.28 189.44 ± 30.22 89.76% -1 BOD5 (mg L ) 991.67 ± 352.81 121.22 ± 80.17 87.78% Phosphorus (mg L-1) 25.30 ± 17.64 12.85 ± 8.12 49.22% Kjeldahl nitrogen (mg L-1) 32.60±17.18 5.02±3.56 84.61% Ammonium nitrogen (mg L-1) 15.15±9.98 2.92±1.88 80.75% Nitrites (mg L-1) 0.65±0.15 1.65±0.45 - Nitrates (mg L-1) 1.51±0.45 4.64±3.15 - The schematic of the experimental unit is shown in Figure 1. The equipment was supplied by PAM Membranes (Rio de Janeiro - Brazil). Samples were stored in a buffer tank, in which a peristaltic pump fed the MBR (6 liter volume). A suction pump (diaphragm) connected to the submerged membrane module produces vacuum inside the membranes, removing permeate (treated effluent). This same pump allows the inversion of the flow, performing the backwashes. Aeration was supplied by a compressor, injecting air at a rate of 4 L min-1, measured by a rotameter and maintaining dissolved oxygen (OD) in the range of 3-4 mg L-1 (analyzed by a digital oximeter). There was a control panel connected to a computer for controlling the operation/backwash cycles, as well as for receiving and storing the MBR information. Level sensors into the permeate tank controlled the purge of permeate by opening a solenoid valve. The membranes used were of hollow fiber ultrafiltration of polyvinylidene supplied by PAM - Selective Membranes. The total length was 0.25 m, the external diameter of the module was 0.075 m, with a filtration area of 0.22 m² and molar weight of cut-off 50 kDa. Rev. Ambient. Água vol. 15 n. 2, e2489 - Taubaté 2020 4 Everton Luis Butzen et al. Figure 1. Experimental diagram of the MBR used for the treatment of mall wastewater. The experimental unit worked for 60 days, keeping the sludge age at 30 days by sludge discharging. The operating cycle was 4 hours of permeation and 30 seconds of backwash. Constant pressure of 40 kPa was used. The hydraulic residence time (HRT) oscillated according to the membrane sealing process, reaching a mean of 4.06 h ± 1.00 h. The bioreactor was inoculated with sludge from an activated sludge system of a dairy industry, previously acclimatized for 30 days. The total suspended solids concentration (TSS) was 3,000 mg L-1 and during the operation it presented a mean concentration of 3,738±930mg L-1. The average pH was 7.59±0.51 and the F/M ratio (Food/Microorganism) was measured by 3.33 d-1 ± 1.43 d-1 (measured by COD). Over time, permeate flux was recorded. Samples of raw and treated (permeate) sewage were collected and analyzed for color, turbidity, COD, BOD5, total phosphorus, total and ammonium nitrogen, nitrites and nitrates. The procedures follow the Standard Methods for the Examination of Water and Wastewater (APHA et al., 2005). 3. RESULTS AND DISCUSSION Table 1 shows the characteristics of the raw wastewater and permeate during the MBR operation, as well as the average removal of the system. Note that the sewage has higher concentration than traditional domestic sewage, which has approximately 300 mg L-1 of BOD, lacking studies for its proper treatment. The MBR system showed high color removal and turbidity reduction, with an average removal of 91.2% and 97.2%, respectively. Bani-Melhem et al. (2015) used the MBR system with submerged UF membrane for the treatment of gray water and obtained removal similar to our work (95.20% for color removal and 96.30% for turbidity). Removal efficiency and stability were mainly attributed to the physical separation of membranes, retaining suspended and colloidal solids. The color and turbidity removal of the MBR is shown in Figure 2. The color quality of the permeate as much as the color removal of turbidity remained stable throughout the operation, as can be observed in Figure 2, regardless of the variations in a broad range of the raw sewage characteristics. Note that the color ranged between ~100 NTU and 1100 NTU. In general, malls discharge the treated effluent into the public sewage network, and turbidity is used to determine a surcharge to the mall establishment. Thus, keeping turbidity low is also important from an economic perspective. Rev. Ambient. Água vol. 15 n. 2, e2489 - Taubaté 2020 Membrane bioreactor for mall wastewater treatment 5 Figure 2. Color removal (a) and turbidity reduction (b) by the MBR treating mall wastewater. The concentration of COD of the raw sewage and permeate from the MBR are presented in Figure 3. The MBR achieved an average COD removal of 89.76%, adjusting the COD of permeate below 225 mg L-1. Note that we used a high F/M (~3.3 d-1) in a range near that which would produce flocculent sludge, but the membrane was capable of removing the SS and colloidal matter in such a way that the effluent was free of cellular material. The SS concentration is variable according to the load fed to the MBR. For example, treating domestic sewage, Maestri (2007) showed that an MBR is capable of removing 88% of COD, operating with a concentration of SS between 1,000 and 2,220 mg L-1; but the wastewater was low in SS concentration. On the other hand, Maqbool et al. (2014) and Komesli et al. (2015) obtained better results, with efficiency varying from 93.3% to 95.1%, but with SS between 11,000 mg L-1 and 12,000 mg L-1 using synthetic effluent and urban wastewater. However, the synthetic wastewater does not have any inhibitors, such as disinfectants or other constituents of real wastewater. Furthermore, we tried augmenting the concentration of SS into the bioreactor, but the system did not raise beyond 6,000 mg L-1. Thus, we attributed this efficiency mainly to concentration of SS in the bioreactor (3,738 mg L-1 ± 930 mg L-1), which can be considered low for a MBR. However, the effluent is free of suspended solids and low in turbidity and color, and could perhaps be a candidate for a post-treatment for reclamation for non-drinking uses. In fact, reuse of domestic wastewater was the main focus of Subtil et al. (2013), where the effluent treated by MBR showed COD, turbidity and color of 24 mg L-1, 0.29 NTU and 25 uC, respectively. However, the COD of raw the wastewater was only one half that of the mall wastewater (approximately of 1,000 mg L-1). Figure 3. Removal of COD in the MBR by treating mall sewage. Rev. Ambient. Água vol. 15 n. 2, e2489 - Taubaté 2020 6 Everton Luis Butzen et al. The COD in the permeate during the MBR operation remained stable with a mean of 189.4 mg L-1 ± 30.2 mg L-1, even with the variations of organic load presented by the raw sewage in Figure 3. Subtil et al. (2013) suggested that COD in the permeate is attributable mainly to the non-biodegradable and non-transformed soluble organic matter that has passed through the physical barrier of the membrane. We used a high organic load, and maybe an overload on activated sludge, and no further degradation of the organic matter was possible. Furthermore, note that a low HRT was enough to reach a COD removal of approximately 90%. The BOD removal reached an efficiency of 87.78%. Rodríguez-Hernández et al. (2014) achieved 96% BOD removal efficiency, attributing the high organic removal efficiency of the MBR to the highest concentration or biomass activity into bioreactor. However, Rodríguez- Hernández et al. (2014) studied municipal wastewater with low COD (377 mg L-1), and the sewage of the mall of our study has higher organic load than the general values of domestic sewage (approximately 300 mg L-1 of BOD). The efficiency of removal of COD and BOD is directly related to the characteristics of the MBR biomass, besides the capacity of retention of solids in suspension and colloidal substances by the membrane. The operation of MBR with high concentrations of SST in the bioreactor can promote better removal of organic matter from the raw sewage, producing a better permeate. Figure 4 shows the phosphorus concentrations of raw and treated sewage and the removal of this parameter by MBR. The concentration of phosphorus in the raw sewage was 25.3 mg L- 1 ± 17.6 mg L-1 and the permeate 12.85 ± 8.12 mg L-1 (removal of 49.22%). This removal is higher than the result of Barbosa et al. (2016), which obtained an efficiency of 33% for phosphorus. In addition, Rodríguez-Hernández et al. (2014) showed a removal in a range of 37% and 42% of phosphorus, for municipal wastewater treated by an MBR, and the removal was attributed to the nutritional need of the microorganisms, disregarding the removal by the phosphorus-accumulating organisms (OAPs) due to the low organic load applied and the high age of the sludge. Furthermore, low F/M rates were responsible for low removals of total phosphorus (20% to 29%) in the work developed by Nguyen et al. (2016). Maqbool et al. (2014) reported that the low 4 h of HRT, associated with the rapid growth of microorganisms was responsible for the typical removal of 41.3 % to 48.2 % achieved in their work. The removal of our work is possibly associated with the combination of all elements: the age of the sludge was around 30 days, a high organic load was applied (F/M = 3.33 d-1) and the HRT was low (4.18 h). This creates a combination where phosphorus is assimilated by microorganisms, and microorganisms are retained by the membrane. We also believed that the presence of phosphates adsorbed on the suspended material and the colloidal substances retained in the membrane have contributed to the excellent performance obtained. Figure 4. Removal and concentration of phosphorus in raw sewage of the mall and in the permeate treated by the MBR. Rev. Ambient. Água vol. 15 n. 2, e2489 - Taubaté 2020 Membrane bioreactor for mall wastewater treatment 7 The introduction of anoxic cycle to MBR can improve the removal of phosphorus. Han et al. (2005) operated an MBR to in the intermittent aeration cycles (non-aeration mix feed, aeration, non-aeration phase, aeration filtration) and the removal of phosphorus was up to 72%. Kellner (2014) and Belli et al. (2014) operated a MBR in sequential batches and an achieved an average efficiency of 70%, which reached 74% efficiency, assigning the available organic matter to microorganisms with determinants for the large biological removal of phosphorus. However, even without the anoxic cycle of our experiments, the MBR achieved a removal similar to those of usual activated sludge processes. In regard to nitrogen removal (Figure 5), the raw sewage fed to the MBR presented an average concentration of 32.60 mg L-1 (standard deviation of 17.18 mg L-1) and permeate was 5.02 mg L-1. The removal of nitrogen remained in the range of 80% to 90% for nearly the entire period of MBR operation, but this value can oscillate over a wide range. For example, Barbosa et al. (2016) performed experiments under constant aeration and a sludge age of 3 days, and a removal efficiency of 81% was achieved. Capodici et al. (2015) observed removal of nitrogen similar to our work (55% to 76%). However, our MBR worked with a low HRT (4 h), whilst Subtil et al. (2014) and Rodriguez-Hernandez et al. (2014) operated the MBR with an HRT of 10 to achieve similar removal of nitrogen (near 80%). Therefore, sewage quality and operational conditions are important and provide different rates of nitrogen removal. Figure 5. Nitrogen removal by the MBR treating mall sewage. We did not use the anoxic cycles to improve denitrification. Thus, we observed the average concentration of nitrites and nitrates of 1.65 mg L-1 and 4.64 mg L-1, respectively, but the average removal of ammonium was 80.7%. Several factors are important to nitrogen removal, but we highlighted three. A) age of sludge: Bani-Melhem et al. (2015) operated a MBR for 42 days with total retention of the sludge; the system removed 88% of nitrogen. The authors reported that nitrifying bacteria requires more time to nitrify the ammonia. Likewise, Capodici et al. (2015) reported that an age of sludge of only 5 days limited the growth of nitrifying bacteria. B) Dissolved oxygen: Chen et al. (2012) attributed low ammonia removal in MBR to low oxygen supplied to the system. C) Anoxic cycle: Belli et al. (2014) reported the removal of ammonia of 99% and total nitrogen of 82% when an MBR was operated in a sequential batch. Barbosa et al. (2016) established nitrification and simultaneous denitrification (NDS) conditions, removing both COD and total nitrogen in a single reactor. However, we kept the age of the sludge at 30 days and the dissolved oxygen above 2 mg L-1. The presence of nitrites in the effluent of the MBR shows that there was nitrification, but denitrification requires the introduction of the anoxic cycle. However, we did not insert the anoxic cycle in our work, and Rev. Ambient. Água vol. 15 n. 2, e2489 - Taubaté 2020 8 Everton Luis Butzen et al. thus we identified nitrites in the treated effluent, although the concentration is low. The average permeate flux and suspended solids of the MBR are presented in Figure 6. We observed an inverse relationship between both parameters: the higher the TSS in the reactor, the lower the permeate flux. The average permeate flux was 7.00 ± 1.84 L h-1 m-2. In fact, we can expect high permeate flux in the operation of MBR for the treatment of wastewater due to the high concentration of suspended solids. The literature also shows low permeate flux in the operation of the MBR for the treatment of different wastewater (6.74 L h-1 m-2). Kellner (2014) used a MBR with submerged hollow fiber membrane for the treatment of sanitary effluents with SST ranging from 3,000 mg L-1 to 5,000 mg L-1 and the permeate flux was 6.74 L h-1 m-2. Huelgas and Funamizu (2010) observed a permeate flux of 9 L h-1 m-2 for wastewater treatment of washing machines and kitchen sinks, suggesting that the high concentration of suspended solids in the bioreactors and the established operating conditions make it impossible to obtain high flows through the membranes. Bani-Melhem et al. (2015) reported that the high concentration of TSS in MBR, higher COD concentrations and inorganic impurities in the raw sewage can have a significant impact on the reduction of flow. In fact, we used the raw sewage from the mall without any treatment, and thus inorganic impurities can impact permeate flux. Figure 6. Average permeate flux and total suspended solids in the MBR. The permeate flux of the MBR over a 24 h period with a 4 h filtration cycle and 30 second back flushes with a constant pressure of 40 kPa is shown in Figure 7. Figure 7. Permeate flux of the MBR in the treatment of mall wastewater during a 24 h period. The permeate flux of the MBR presented a strong reduction in the first minutes of operation and a smooth reduction in the later period, achieving some stability in the range of 5 L h-1 m-2 Rev. Ambient. Água vol. 15 n. 2, e2489 - Taubaté 2020 Membrane bioreactor for mall wastewater treatment 9 to 10 L h-1 m-2. After the back flushes, the permeate was recovered, reaching 60 L h-1 m-2–70 L h-1 m-2. The recovery of the initial permeate flux indicates that pore clogging of the membrane was fully reversible. The low resistance of pore clogging was also observed by Zhang et al. (2014), as they identified that fouling is the major filtration resistance. Belli et al. (2014) studied an MBR for nutrient removal from municipal sewage and identified the presence of polysaccharides and proteins (major agents of fouling in MBR) in the reactor. In fact, exopolysaccharides (EPS) are mainly responsible for fouling in the MBR (Drews et al., 2006). However, in our experiments we can recover the permeate over the 60 days without any chemical cleaning. Melin et al. (2006) suggest the installation of preliminary MBR treatments to reduce membrane fouling and extend the cycle of operation. Finally, camparing the MBR with conventional activated sludge, Hao et al. (2018) developed a method to measure the benefits with regard to the sustainability and economic viability of both processes. In contrast to previous studies, the indexes created by Hao et al. (2018) showed that the MBR is not a more sustainable process when compared to conventional activated sludge. We disagree, due to the simple fact that the quality of effluent of MBR will be higher than the effluent from conventional activated sludge. In the course of time, the MBR will also be economically competitive. 4. CONCLUSIONS The MBR system is an alternative with great potential for application in the treatment of sewage from malls and establishments generating effluents with high organic load. The system presented great removal of color and turbidity, reaching average efficiency of 91.20% and 97.20%, respectively. The COD and BOD removal was 89% and 87%, respectively. Furthermore, the permeate quality was stable, even with variations in the organic load of the raw wastewater. The MBR, despite the fact that we did not use the anoxic cycle, removed nutrients with good performance. The average removal of phosphorus reached was 49% and total nitrogen removal was 84%. The nitrification process was influenced by the age of the sludge maintained at 30 days and the amount of oxygen supplied to the bioreactor. The introduction of an anoxic phase into the MBR operating cycle could provide simultaneous nitrification and denitrification processes. The MBR presented an average permeate of 7.00 L h-1 m-2, with the oscillations related mainly to the variation of biomass concentration in the bioreactor. Despite a strong drop of permeate flux in the initial minutes, membrane fouling was reversible and was controlled by backflushes. 5. REFERENCES APHA; AWWA; WEF. Standard Methods for the Examination of Water and Wastewater. 21. ed. Washington, 2005. BANI-MELHEM, K.; AL-QODAHB, Z.; AL-SHANNAGC, M.; A QASAIMEHD, A.; QTAISHATC, M. R.; ALKASRAWI, M. On the performance of real grey water treatment using a submerged membrane bioreactor system. Journal of Membrane Science, v. 476, p. 40-49, 2015. https://doi.org/10.1016/j.memsci.2014.11.010 BARBOSA, I. M.; MIERZWA, J. C.; HESPANHOL, I.; SUBTIL, E. L. Remoção de matéria orgânica e nitrogênio em biorreator com membranas submersas operando em condição de nitrificação e desnitrificação simultâneas. Revista Ambiente & Água, v. 11, n. 2, p. 304-315, 2016. http://dx.doi.org/10.4136/ambi-agua.1684 Rev. Ambient. Água vol. 15 n. 2, e2489 - Taubaté 2020 10 Everton Luis Butzen et al. BELLI, T. J.; BERNARDELLI, J. K. B.; AMARAL, P. A. P.; COSTA, R. E.; AMARAL, M. C. S.; LAPOLLI, F. R. Biological nutrient removal in a sequencing batch membrane bioreactor treating municipal wastewater. Desalination and Water Treatment, p. 1-8, 2014. https://doi.org/10.1080/19443994.2014.952961 CAPODICI, M.; DI BELLA, G.; DI TRAPANI, D.; TORREGROSSA, M. Case study: pilot scale experiment with MBR operated in intermittent aeration condition: analysis of biological performance. Bioresource Technology, v. 177, p. 398-405, 2015. https://doi.org/10.1016/j.biortech.2014.11.075 CHEN, W.; LIU, J.; XIE, F. Identification of the moderate SRT for reliable operation in MBR. Desalination, v. 286, p. 263–267, 2012. https://doi.org/10.1016/j.desal.2011.11.033 DREWS, A.; LEE, C.H.; KRAUME, M. Membrane fouling: A review on the role of EPS. Desalination, v. 200, p. 186–188, 2006. http://dx.doi.org/10.1016/j.desal.2006.03.290 HAN, S. S.; BAE, T. H.; JANG, G. G.; TAK, T. M. Influence of sludge retention time on membrane fouling and bioactivities in membrane bioreactor system sp. Process Biochemistry, n. 40, p. 2393–2400, 2005. https://doi.org/10.1016/j.procbio.2004.09.017 HAO, X.D.; LIA, J.; van LOOSDRECHT, M. C. M.; LIA, T.Y. A sustainability-based evaluation of membrane bioreactors over conventional activated sludge processes. Journal of Environmental Chemical Engineering, v. 6, p. 2597–2605, 2018. https://doi.org/10.1016/j.jece.2018.03.050 HUANG, L.; LEE, D. J. Membrane bioreactor: A mini review on recent R&D Works sp. Bioresource Technology, v. 194, p. 383–388, 2015. https://doi.org/10.1016/j.biortech.2015.07.013 HUELGAS, A.; FUNAMIZU, N. Flat-plate submerged membrane bioreactor for the treatment of higher-load greywater. Desalination, v. 250, n. 1, p. 162-166, 2010. https://doi.org/10.1016/j.desal.2009.05.007 KELLNER, R. L. Biorreator à membrana de leito móvel em bateladas sequenciais para a remoção de nutrientes e matéria orgânica de efluentes sanitários 2014. 146 f. Dissertação (Mestrado em Engenharia Sanitária e Ambiental) - Universidade Federal de Santa Catarina, Florianópolis, 2014. KESKES, S.; HMAIE, F.; GANNOUN, H.; BOUALLAGUI, H.; GODON, J. J.; HAMDI, M. Performance of a submerged membrane bioreactor for the aerobic treatment of abattoir wastewater. Bioresource Technology, n. 103, p. 28-34, 2012. https://doi.org/10.1016/j.biortech.2011.09.063 KOMESLI, O. T.; MUZ, M.; AK, S.; GÖKÇAY, C. F. Prolonged reuse of domestic wastewater after membrane bioreactor treatment. Desalination and Water Treatment, n. 53, p. 3295-3302, 2015. https://doi.org/10.1080/19443994.2014.934107 KRZEMINSKI, P.; LEVERETTE, L.; MALAMIS, S.; KATSOU, E. Membrane bioreactors. A review on recent developments in energy reduction, fouling control, novel configurations, LCA and market prospects. Journal of Membrane Science, v. 527, p. 207-227, 2017. https://doi.org/10.1016/j.memsci.2016.12.010 MAESTRI, R. S. Biorreator à membrana como alternativa para o tratamento de esgotos - anitários e reuso da água. 2007. 101 f. Dissertação (Mestrado em Engenharia Ambiental) - Universidade Federal de Santa Catarina, Florianópolis. 2007. Rev. Ambient. Água vol. 15 n. 2, e2489 - Taubaté 2020 Membrane bioreactor for mall wastewater treatment 11 MAQBOOL, T.; KHAN, S. J.; LEE, C. H. Effects of filtration modes on membrane fouling behavior and treatment in submerged membrane bioreactor. Bioresource Technology, v. 172, p. 391–395, 2014. https://doi.org/10.1016/j.biortech.2014.09.064 MELIN, T.; JEFFERSON, B.; BIXIO, D.; THOEYE, C.; DE WILDE, W.; DE KONING, J.; VAN DER GRAAF, J.; WINTGENS, T. Membrane bioreactor technology for wastewater treatment and reuse. Desalination, v. 187, p. 271-282, 2006. https://doi.org/10.1016/j.desal.2005.04.086 NEOH, C. H.; NOOR, Z. Z.; MUTAMIM, N. S. A.; LIM, C. K. Green technology in wastewater treatment technologies: Integration of membrane bioreactor with various wastewater treatment systems. Chemical Engineering Journal, v. 283, p. 582-594, 2016. https://doi.org/10.1016/j.cej.2015.07.060 NGUYEN, T. T; BUI, X. T; VO, T. D. H; NGUYEN, D. D.; NGUYEN, P. D; DO H. L. C; NGO, H. H; GUO, W. Performance and membrane fouling of two types of laboratory- scale submerged membrane bioreactors for hospital wastewater treatment at low flux condition sp. Separation and Purification Technology, v. 165, p. 123-129, 2016. https://doi.org/10.1016/j.seppur.2016.03.051 PRANEETH, K.; MOULIK, S.; VADTHYA, P.; BHARGAVA, S. K. Performance assessment and hydrodynamic analysis of a submerged membrane bioreactor for treating dairy industrial effluent. Journal of Hazardous Materials, v. 274, p. 300–313, 2014. https://doi.org/10.1016/j.jhazmat.2014.04.030 RODRÍGUEZ-HERNÁNDEZ, L.; ESTEBANGARCÍA, A. L.; TEJERO, I. Comparison between a fixed bed hybrid membrane bioreactor and a conventional membrane bioreactor for municipal wastewater treatment: a pilot scale study. Bioresource Technology, v. 152, p. 212-219, 2014. https://doi.org/10.1016/j.biortech.2013.10.081 SUBTIL, E. L.; HESPANHOL, I.; MIERZWA, J. C. Biorreatores com membranas submersas (BRMs): alternativa promissora para o tratamento de esgotos sanitários para reuso sp. Revista Ambiente & Água, v. 8, n. 3, 2013. https://doi.org/10.4136/ambi-agua.1230 SUBTIL, E. L.; HESPANHOL, I.; MIERZWA, J. C. Comparison between a conventional membrane bioreactor (C-MBR) and a biofilm membrane bioreactor (BF-MBR) for domestic wastewater treatment. Brazilian Journal of Chemical Engineering, v. 31, n. 3, p. 683 – 691, 2014. https://doi.org/10.1590/0104-6632.20140313s00002890 VILLAIN, M.; MARROT, B. Influence of sludge retention time at constant food to microorganism ratio on membrane bioreactor performances under stable and unstable state conditions. Bioresource Technology, n. 128, p. 134-144, 2013. https://doi.org/10.1016/j.biortech.2012.10.108 ZHANG, Y.; ZHANG, M.; WANG, F.; HONG, H.; WANG, A.; WENG, X.; LIN, H. Membrane fouling in a submerged membrane bioreactor: Effect of pH and its implications. Bioresource Technology, v. 152, p. 7-14, 2014. https://doi.org/10.1016/j.biortech.2013.10.096 Rev. Ambient. Água vol. 15 n. 2, e2489 - Taubaté 2020 Ambiente & Água - An Interdisciplinary Journal of Applied Science ISSN 1980-993X – doi:10.4136/1980-993X www.ambi-agua.net E-mail: [email protected] Sorption of Remazol Black B dye in alluvial soils of the Capibaribe River Basin, Pernambuco, Brazil ARTICLES doi:10.4136/ambi-agua.2491 Received: 05 Nov. 2019; Accepted: 19 Feb. 2020 Adriana Thays Araújo Alves1* ; Luisa Thaynara Muricy de Souza Silva1 ; Lucas Ravellys Pyrrho de Alcântara2 ; Vitor Hugo de Oliveira Barros3 ; Severino Martins dos Santos Neto2 ; Valmir Félix de Lima2 ; José Romualdo de Sousa Lima4 ; Artur Paiva Coutinho1 ; Antonio Celso Dantas Antonino2 1Núcleo de Tecnologia. Universidade Federal de Pernambuco (UFPE), Avenida Marielle Franco, S/N, Km 59, CEP: 55014-900, Caruaru, PE, Brazil. E-mail: [email protected], [email protected] 2Departamento de Energia Nuclear. Universidade Federal de Pernambuco (UFPE), Avenida Professor Luiz Freie, n° 1000, CEP: 53740-545, Recife, PE, Brazil. E-mail: [email protected], [email protected], [email protected], [email protected] 3Instituto Federal do Sertão Pernambucano, Rodovia PE 320, S/N, km 126, Zona Rural, Caixa Postal 78, Serra Talhada, PE, Brazil. E-mail: [email protected] 4Unidade Acadêmica de Garanhuns. Universidade Federal Rural de Pernambuco (UFRPE), Avenida Bom Pastor, S/N, CEP: 555292-278, Garanhuns, PE, Brazil. E-mail: [email protected] *Corresponding author. E-mail: [email protected] ABSTRACT Wastewater from textile industries is loaded with synthetic dyes. These effluents are often not adequately treated, affecting the soil and groundwater quality and leading to environmental contamination. The Agreste mesoregion of the state of Pernambuco is home to one of the largest textile centers in Brazil. This work therefore aims to study the behavior of Remazol Black B (RB5) dye in subsurface mediums in this region. The kinetics and isotherm sorption experiments allowed an evaluation of RB5 retention capacity in two layers of alluvial soil of the dry riverbed of the Capibaribe Basin. The maximum sorption rate was 81.81 mg kg-1 and 21.7 mg kg-1 for the loamy sand and sand layers, respectively. The Pseudo-second order kinetic model described more appropriately the sorption kinetics for both soils. The isotherms behavior was nonlinear, and Freundlich model was the most suitable to describe this process for both -1 -1 soils, presenting KF values of 8.6407 L kg for loamy sand and 0.1868 L kg for sand. The isotherm parameters confirm a more significant interaction of RB5 with the loamy sand layer than with the sand layer, indicating lower leaching in the first layer, which is less mobile for RB5 contamination. Furthermore, the different sorption rates for both soils indicate the importance of studying the soil as a heterogeneous profile. Keywords: isotherm, kinetics, mobility. Sorção de corante Remazol Black B em solos aluviais da Bacia do Rio Capibaribe Pernambuco, Brasil RESUMO As águas residuais das indústrias têxteis são carregadas com corantes sintéticos. Esses This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 Adriana Thays Araújo Alves et al. efluentes geralmente não são tratados adequadamente, afetando a qualidade do solo e das águas subterrâneas, levando à contaminação ambiental. O Agreste de Pernambucano abriga um dos maiores centros têxteis do Brasil. Portanto, este trabalho tem como objetivo estudar o comportamento do corante Remazol Black B (RB5) em meios subsuperficiais nessa região. Os experimentos de cinética e sorção isotérmica permitiram avaliar a capacidade de retenção do RB5 em duas camadas de solo aluvial do leito seco do rio Capibaribe. A taxa máxima de sorção foi de 81,81 mg kg-1 e 21,7 mg kg-1 para a camada areia franco e camada areia, respectivamente. O modelo cinético de pseudo-segunda ordem descreveu mais adequadamente a cinética de sorção para ambos os solos. O comportamento das isotermas foi não-linear e o modelo de Freundlich foi o mais adequado para descrever esse processo para ambos os solos, apresentando -1 -1 valores de KF de 8,6407 L kg para areia franco e 0,1868 L kg para areia. Os parâmetros isotérmicos confirmam uma interação mais significativa do RB5 com a camada de areia franco do que com a camada de areia, indicando menor lixiviação na primeira camada, menos móvel para a contaminação por RB5. Além disso, as diferentes taxas de sorção para os dois solos indicam a importância do estudo do solo como um perfil heterogêneo. Palavras-chave: cinética, isotérmica, mobilidade. 1. INTRODUCTION The Agreste of the state of Pernambuco is inserted in the Brazilian semi-arid region, configuring a region marked by low rainfall, high evapotranspiration rates, and intermittent rivers with flow only in the rainy season (Braga, 2016). In the absence of surface water resources, many rural communities in this region use underground reservoirs, such as alluvial deposits, by digging wells in the dry riverbed (Braga et al., 2015). These formations attract several anthropogenic activities, increasing the contamination risk of the alluvial deposits’ water reserves. In this region of the Agreste of Pernambuco is concentrated the so-called “Textile Center”, encompassing municipalities such as Santa Cruz do Capibaribe, Toritama, Caruaru and Brejo da Madre de Deus (SEBRAE, 2013). This activity has negative impacts due to the release of untreated effluents, which have caused severe environmental contamination problems in the region. Wastewater from these industries is a complex mix of dyes and heavy-metal compounds (Shalaby et al., 2017). In textile manufacturing, the dyeing step is the most substantial process in terms of time, added value, and technical complexity (Huynh and Chien, 2018). This step includes the dyeing itself and the washing to remove the non-fiber dye, releasing 10 to 15% into wastewater (Jayanthy et al., 2014). Kharat (2015), reported cases where the indiscriminate discharge of textile effluents has affected soil and groundwater quality. In this way, some synthetic dyes are soil pollutants that concern researchers due to the toxic nature and adverse effect on life forms (Smaranda et al., 2017). Regarding this, azo dyes are carcinogenic in nature (Jayanthy et al., 2014; Stagnaro et al., 2015). This dye typology is characterized by having one or more double nitrogen bonds (- N = N-) (Jayanthy et al., 2014), and approximately half of the world's industrial production belongs to this class (Stagnaro et al., 2015). The intense textile activity in the Agreste of Pernambuco and the importance of conserving the scarce surface and groundwater in the region make necessary the development of studies to assess the impact of manufacturing activity on the subsurface. Therefore, environmental contamination can be estimated in the laboratory by batch testing, allowing the analysis of kinetics and sorption isotherm. Sorption is often used to evaluate soil retention capacity for a compost and the potential loss via leaching (Wei et al., 2019). From this perspective, this work evaluates through sorption kinetics and isotherm the Rev. Ambient. Água vol. 15 n. 2, e2491 - Taubaté 2020 Sorption of Remazol Black B dye in … 3 retention and mobility of the Remazol Black B (RB5) azo dye, which is widely used by the textile industry in the semi arid region of Pernambuco state. For this purpose, two layers of alluvial soil of the dry riverbed of the Capibaribe basin in the mesoregion of the Agreste of Pernmabuco’s state will be analyzed. 2. MATERIALS AND METHODS 2.1. Study area The studies were conducted in the High Capibaribe region, which embraces the highest portion of the Capibaribe River watershed in the state of Pernambuco. Soil samples were collected at the coordinates 7º56'57.6” S and 36º17'57.2” W in the dry riverbed, in the portion between the municipalities of Santa Cruz do Capibaribe and Brejo da Madre de Deus. Soil samples were collected from the first two soil layers with Layer 1 (CM 1) presenting a maximum thickness of 52 cm and Layer 2 (CM 2) dimension ranging between 17 and 81 cm. Subsequently, the particle-size distribution, pH in water, and Zero Charge Point (ZCP) according to the EMBRAPA (1997) methods were analyzed. The parameters of organic matter -1 -1 -1 (OM) (g g ), organic carbon (OC) (g g ) and cation exchange capacity (CEC) (cmolc dm ) were obtained by analyses of soils already made by Rabelo (2018). 2.2. Dyes and solutions In this study Reactive Black 5 (RB5) dye (Color Index - Reactive Black 5, RB5, C26H21N5Na4O19S6) was chosen as the model dye. RB5 is a reactive and anionic dye, belonging to the Azo class. RB5 is identified as a dye popularly used by the textile industry (Felista et al., 2020; El Bouraie and El Din, 2016). Large amounts of RB5 are discharged in the watercourses in developing countries (El Bouraie and El Din, 2016); also, this dye is commonly found in dyebath effluents in higher concentrations than other reactive dyes (Pekakis et al., 2006). Finally, the problem of contamination by RB5 has motivated several studies found in the national literature (Pereira et al., 2019; Cruz Filho et al., 2016; Cruz et al., 2016; Cardoso et al., 2011; Souza et al., 2010). In order to simulate the actual dyeing process conditions used in the textile industries, the RB5 solution was initially subjected to hydrolysis. In this procedure, the initial pH of the solution was adjusted to 12.0 ± 0.05, with the addition of 20% (w / v) sodium hydroxide. Then, the solution was heated for 60 minutes at 80 ± 2°C and stirred on a magnetic stirrer. Subsequently, the solution was cooled to the ambient temperature, and the pH was adjusted by adding hydrogen sulfide (0.1N) to 7.0 ± 0.05. Similar hydrolysis procedures were verified in studies developed by Cunico et al. (2015) and Albuquerque et al. (2005). 2.3. Sorption kinetics For the kinetic study, a solution of RB5 at a concentration of 25 mg L-1 was prepared by dissolving 50 mg of RB5 in 2 L of distilled water. This value is within the dye concentration range for the textile effluent according to El Bouraie and El Din (2016). After the hydrolysis process, the solution was distributed in Erlenmeyers of 100 ml and assuming the soil/solution proportion of 1:10 (5 g of soil to 50 ml of RB5 solution). All samples were prepared in triplicate and stirred at 200 rpm on an orbital shaker for the times of 0.17, 0.5, 1, 3, 5, 8, 10, 16, 24, 48, and 72 hours. The experiment was performed at a temperature of 24 ± 2°C. In addition, after the samples were removed from the shaker, they were filtered through 0.45 µm sterile membrane filters. The quantification of the dye concentration in the samples was evaluated by reading the absorbance at the wavelength identified by the scan (597 nm) using the Thermo Scientific GENESYS 30 Vis Spectrophotometer. Rev. Ambient. Água vol. 15 n. 2, e2491 - Taubaté 2020 4 Adriana Thays Araújo Alves et al. 2.4. Sorption Kinetics Modelling The results of the kinetic study were adjusted to the Pseudo-first order, Pseudo-second order, and Intra-particle diffusion models. The Pseudo-first order model is expressed according to Equation 1 (Lagergren, 1898). −푘1푡 푞푡 = 푞푒1(1 − 푒 ) (1) -1 Where 푞푒1 and 푞푡 are the amounts of dye adsorbed by soil mass (mg kg ) at equilibrium -1 and by time (h), respectively, and 푘1 (h ) is the Pseudo-first order constant. The Pseudo-second order model is expressed according to Equation 2 (Ho and Mckay, 1999). 2 푞푡 = 푘2푞푒2 푡 + 푞푒2 (2) -1 Where 푞푒2 is the amount of dye adsorbed by soil mass (mg kg ) for the second-order model -1 -1 and 푘2 (kg h mg ) is the constant of the Pseudo-second order model. The intra-particle diffusion model is expressed according to Equation 3 (Weber and Morris, 1963). 1 푞푡 = 푘푖푡2 + 푐 (3) 1 -1 Where 푘푖 (mg kg ℎ2) is the constant of the Intra-particle Diffusion model. 2.5. Sorption isotherms A RB5 solution was prepared at a concentration of 40 mg L-1 to perform the isotherm experiments. After performing the hydrolysis, the concentrations of 10; 15; 20; 25; 30; 35 mg L-1 were obtained by dissolution. The tests were prepared in triplicate, maintaining the proportion of 5 g of soil to 50 ml of solution used in the kinetics. All samples were stirred at 200 rpm on an orbital shaker until the equilibrium time determined in the kinetics was reached. Afterward, they were filtered with 0.45 µm sterile membrane filters and the dye concentrations in the samples were determined by absorbance measurement. 2.6. Sorption Isotherms Modelling Sorption isotherms were adjusted to the linear and nonlinear Freundlich models. At ambient concentrations, the sorption isotherm of organic pollutants in the soil can often be considered linear and represented by Equation 4 (Martins and Mermoud, 1999). 푞푒 = 푘퐷퐶푒 (4) -1 Where 퐶푒 is the RB5 concentration in the solution (mg L ) and 푘퐷 is the distribution coefficient for the linear model (L kg-1). Freundlich adsorption isotherm considers the surface heterogeneity and assumes that sorption occurs at sites with different sorption energies, being expressed in the nonlinear form according to Equation 5 (Freundlich and Heller, 1939). 1 n qe= KFCe (5) -1 -1 Where 퐾퐹 is the Freundlich constant (L kg ) and n is the affinity coefficient (kg L ). A considerable portion of organic compounds sorption in soils is attributed to the organic Rev. Ambient. Água vol. 15 n. 2, e2491 - Taubaté 2020 Sorption of Remazol Black B dye in … 5 content of the matrix. Therefore, it is essential to investigate the normalized sorption coefficient of the organic carbon (퐾푂퐶), which is expressed by Equation 6. 푘 퐾 = 푤 (6) 푂퐶 푓푐표 Where 푘푤 is the soil partition coefficient and 푓푐표 is the fraction of the soil organic content. Therefore, the lower the Koc value is, the higher the concentration of the compound in solution is and higher values indicate a tendency for chemical substances to be sorbed by the soil particles (Gavrilescu, 2005). 3. RESULTS AND DISCUSSION 3.1. Soil characterization The results of the analyses for the soils are shown in Table 1. For granulometric analysis, the test was performed in duplicate, while PH and ZCP were performed in triplicate, the respective standard deviations are presented. Table 1. Main characteristics of the analyzed soils. OM * OC * CEC * Layer Sand % Silt % Clay % pH in water ZCP -1 -1 -3 (g g ) (g g ) (cmolc dm ) 79.395 ± 0.35 15.71 ± 0.20 4.895 ± 0.35 CM 1 8.26 ± 0.28 5.50 ± 0.20 2.17% 1.26% 7.4 Loamy sand 95.48 ± 0.40 4.205 ± 0.35 0.315 ± 0.29 CM 2 6.01 ± 0.35 6.00 ± 0.35 1.67% 0.97% 3.3 Sand * Rabelo (2018) ± standard deviation. 3.2. Sorption Kinetics The kinetic study shows that CM 2 (Sand) reaches equilibrium time for RB5 sorption faster than CM 1 (Loamy Sand). Layers CM 1 and CM 2 achieved equilibrium at 16 and 10 hours, respectively, and the maximum sorption was 81.81 mg kg-1 for CM 1 and 21.7 mg kg-1 for CM 2. Alexandre (2019), analyzed the sorption of Direct Black 22 dye for the same soils of this study, finding an equilibrium time of 8 and 4 hours for CM 1 and CM 2, respectively. The first layer adsorbed 122 mg kg-1, while the amount adsorbed in the second layer was 40 mg kg-1. Therefore, these data corroborate with the present study regarding the higher sorption capacity of CM 1. The anionic or cationic nature of dyes can be used as the first parameter to understand the mechanisms involved in the sorption process of these compounds in soils. Depending on the soil pH, anionic dyes may bind to non-specific anion exchange sites such as Iron and Aluminum oxides (Ketelsen and Meyer-Windel, 1999). On the one hand, when pH is lower than ZCP, the matrix has a positively charged surface. On the other hand, if the matrix has a pH higher than ZCP, the surface is negatively charged (Dawodu and Akpomie, 2016; Bachratá et al., 2013). Positively charged surfaces favor the sorption of anionic species, while negatively charged surfaces favor the sorption of cationic species (Dawodu and Akpomie, 2016). In this sense, analyzing the sorption of Acid Yellow 23 dye in soils, Dawodu and Akpomie (2016) highlighted that due to the anionic nature of the dye, it will be attracted by a positively charged adsorbent surface, being the sorption optimal for pH lower than the ZCP of the soil, which was 5.8. Rev. Ambient. Água vol. 15 n. 2, e2491 - Taubaté 2020 6 Adriana Thays Araújo Alves et al. The pH of CM 1 is higher than the ZCP value, and for CM 2, the value is approximately equal, indicating that the analyzed soils have a low retention potential for the anionic RB5. The experimental data of the kinetic study with the corresponding adjustments to Pseudo- first order, Pseudo-second order and Intra-particle diffusion models for CM 1 (Figure 1 a) and CM 2 (Figure 1 b) can be seen in Figure 1. First, there is a rapid increase in sorption, which is followed by a slow rise until equilibrium is achieved, indicating the amount for which the adsorbed dye remains approximately constant. Figure 1. Kinetics studies and adjustments for the Pseudo-first order, Pseudo-second order and Intra-particle diffusion models for CM 1 (a) and CM 2 (b). The parameters concerning the adjustments of Pseudo-first order, Pseudo-second order, and Intra-particle diffusion are displayed in Table 2. Both Pseudo-first order and Pseudo-second order models describe well the experimental data for both soil layers. However, qe1 and qe2 estimated values, which were similar to the real ones, and the determination coefficients (R2), which are near to one, showed best adjustments to the Pseudo-second order model. Studying the sorption of the anionic dye Acid Yellow 23 in a Nigerian soil, Dawodu and Akpomie (2016) also found a good fit for the Pseudo-first order (R2 = 0.977) and Pseudo-second order (R2 = 0.978) models, indicating the occurrence of several simultaneous processes that are involved in sorption. In the Pseudo-second order model, chemisorption is the rate-limiting step and sorption capacity is proportional to the number of active sites occupied on the sorbent (Ho and Mckay, 1999). For intra-particle diffusion model, Rev. Ambient. Água vol. 15 n. 2, e2491 - Taubaté 2020 Sorption of Remazol Black B dye in … 7 it is observed that the lines do not pass through the origin, indicating that the intra-particle diffusion is not the only mechanism controlling the adsorption rate (Jiang et al., 2019), which is also confirmed by the low determination coefficient for both soil layers. Table 2. Kinetics parameters for RB5 sorption for CM 1 and CM 2. Model Parameter CM 1 CM 2 -1 k1 (h ) 1.1244 3.6515 -1 Pseudo-first order model qe1 (mg kg ) 78.5674 20.5762 R2 0.9886 0.9892 -1 -1 k 2 (kg h mg ) 0.0116 0.0792 -1 Pseudo-second order model qe2 (mg kg ) 83.4193 21.9957 R2 0.9997 0.9998 1 -1 7.4206 1.5372 Intra-particle diffusion ki (mg kg ℎ2) R2 0.9572 0.9525 The applicability of the Pseudo-second order model to describe RB5 sorption kinetics in both soils is validated by the linearity, as shown in Figure 2 through the plotted graph of t/qt values versus time. Figure 2. Adjustment to the Pseudo-second order model for CM 1 and CM 2. 3.3. Sorption Isotherms The parameters for the linear and nonlinear modeling are shown in Table 3. It was observed that the RB5 sorption isotherms for both soil layers were nonlinear, and they were satisfactorily described by the Freundlich model (R²> 0.9). Freundlich isotherms model also satisfactorily described the sorption of Thioflavin dye in sediments taken from the banks of the Váh River, in Šaľa city, Slovak Republic (Bachratá et al., 2013), and of Basic Yellow X-5GL, Basic Red 13, Direct Blue 86, Vat Yellow 2 and Mordant Black 11 dyes in sediments from the Qinghe River (Liu et al., 2001). Other studies Rev. Ambient. Água vol. 15 n. 2, e2491 - Taubaté 2020 8 Adriana Thays Araújo Alves et al. also reported a good correlation of the Freundlich equation with experimental data of dye sorption in soils, such as the Acid Yellow 23 (Dawodu and Akpomie, 2016), Basic Blue 9 (Sana and Jalila, 2016), Congo Red (Smaranda et al., 2011), and Acid Red 14 dye (Qu et al., 2008). Table 3. RB5 Sorption parameters for the linear and Freundlich models. Model Parameter CM 1 CM 2 푘 (L kg-1) 5.2867 0.9996 Linear 퐷 R2 0.9478 0.9082 -1 KF (L kg ) 8.6407 0.1868 Freundlich R2 0.9970 0.9962 n (kg L-1) 1.1959 0.6659 The results presented for both kD and KF confirm a more significant interaction of RB5 solution with CM 1 than with CM 2. These parameters are used to estimate the degree of pollutants sorption in soils. Therefore, higher values, such as that verified for CM 1, indicate a higher tendency of sorption in the solid matrix, and smaller values, such as CM 2, imply weaker interactions between the dye and the matrix, resulting in greater mobility. The coefficient n for CM 1 indicates sorption closer to the linear. The results of KF enabled the determination of Koc, obtaining values of 685.8 and 19.2 L kg-1 for CM 1 and CM 2, respectively. These values indicate for CM 1 a higher tendency of these particles being sorbed by the soil. The inverse effect is verified for CM 2, for which the Koc value implies a higher susceptibility to leaching losses. The graphs corresponding to Freundlich model adjustments for CM 1 and CM 2 are shown in Figure 3. Figure 3. Freundlich isotherms for CM 1 and CM 2. Considering the chemical composition of the sediment, it can be stated that its organic and inorganic components will significantly affect the sorption capacity (Bachratá et al., 2013). Regarding the organic component, Liu et al. (2001) verified a decrease in sorption of the anionic Rev. Ambient. Água vol. 15 n. 2, e2491 - Taubaté 2020 Sorption of Remazol Black B dye in … 9 dyes Mordant Black 11 and Direct Blue 86 (25% and 40%, respectively), in a fluvial soil after OC removal by H2O2 treatment. Therefore, the higher content of this component in CM 1 than in CM 2 (1.26% and 0.97% of OC for CM 1 and CM 2, respectively) and the respective maximum sorption capacities indicate the influence of soil organic component on RB5 sorption. Besides the organic content, the dye molecules, in general, have a strong affinity with clay minerals. The clay fraction of the soils was identified as predominant in the sorption of the Bright Blue anionic dyes (Ketelsen and Meyer-Windel, 1999) and RB5 (Lazaridis and Keenan, 2010). Lazaridis and Keenan (2010) analyzed the sand, silt, and clay fractions before and after RB5 sorption and they found that only the clay fraction showed a significant displacement in its absorbance peak. Therefore, suggesting that no considerable sorption phenomenon occurred for silt and sand fractions (Lazaridis and Keenan, 2010). For cationic dyes, it is expected a more significant interaction with the clay content than for the anionic dyes such as RB5. In this sense, in the sorption of three dyes in clays, Elmoubarki et al. (2015) found a higher sorption capacity for cationic dyes Methylene Blue and Malachite Green than for anionic dye Methyl Orange. This is because clay has a higher capacity for cation exchange than for anion exchange due to its negatively charged layers (Errais et al., 2012). However, the presence of kaolinite with acid surfaces favors the sorption of anionic dyes because these minerals are the main adsorbent sites for these dyes (Errais et al., 2012). Consequently, the higher retention of RB5 was verified for CM 1 and is correlated to the clay content in soils (clay content of 4.895% for CM 1 and 0.315% for CM 2). 4. CONCLUSIONS Sorption kinetics was best described by the Pseudo-second order model. The kinetic sorption rates show the influence of soil characteristics, such as organic content and clay content, on the RB5 sorption process. This difference in sorption capacity for soils demonstrates the importance of studying the soil as a heterogeneous medium, in which there are different behaviors of contaminants’ dissipation. The isotherms had a nonlinear behavior for both soil layers, with the experimental data satisfactorily adjusted to the Freundlich model. The isotherm parameters confirmed a more significant interaction of RB5 with the loamy sand layer (CM 1) than with the sand layer (CM 2), indicating a lower leaching capability in the upper layer than in the lower layer, which is more mobile for RB5 contamination. 5. ACKNOWLEDGMENTS This work was carried out with the support of the project "Transfer of Water and Mixtures of Reactive Pollutants in Anthropized Soils" (CNPq process No. 436875/2018-7) and of the Foundation for the Support of Science and Technology of the State of Pernambuco (FACEPE/CAPES process IBPG-0125-3.01/17), and by project “National Observatory of Water and Carbon Dynamics in the Caatinga Biome ONDACBC (CNPq process N° 465764/2014-2; CAPES process N° 88887.136369/2017-00; FACEPE process APQ-0498- 3.07/17). 6. REFERENCES ALBUQUERQUE, M. G. E.; LOPES, A. T.; SERRALHEIRO, M. L.; NOVAIS, J. M.; PINHEIRO, H. M. Biological sulphate reduction and redox mediator effects on azo dye decolourisation in anaerobic–aerobic sequencing batch reactors. Enzyme And Microbial Technology, v. 36, n. 5-6, 2005. https://doi.org/10.1016/j.enzmictec.2005.01.005 Rev. Ambient. Água vol. 15 n. 2, e2491 - Taubaté 2020 10 Adriana Thays Araújo Alves et al. ALEXANDRE, J. I. da S. Análise da sorção do corante DB22 em solo aluvionar para Compor um sistema alagado construído. 2019. 102f. Dissertação (Mestrado em Engenharia Civil e Ambiental) - Universidade Federal de Pernambuco, Recife, 2019. BACHRATÁ, M.; ŠUŇOVSKÁ, A.; HORNÍK, M.; PIPÍŠKA, M.; AUGUSTÍN, J. Sorption of Synthetic Dyes Onto River Sediments: A Laboratory Study. Nova Biotechnologica et Chimica, v. 12, n. 1, 2013. BRAGA, R. A. P. As águas invisíveis nos rios intermitentes. In: BRAGA, R. A. P. Águas de areias. Recife: Clã, 2016. p. 11-37. BRAGA, R. A. P.; FARIAS, C. R. de O.; SILVA, S. R. da; CAVALCANTI, E. R. Gestão e educação socioambiental na Bacia do Capibaribe. Recife: Clã, 2015. 140 p. CARDOSO, N. F.; PINTO, R. B.; LIMA, E. C.; CALVETE, T.; AMAVISCA, C. V.; ROYER, B.; CUNHA, M. L.; FERNANDES, T. H. M.; PINTO, I. S. Removal of remazol black B textile dye from aqueous solution by adsorption. Desalination, v. 269, n. 1-3, p.92-103, 2011. https://doi.org/10.1016/j.desal.2010.10.047 CRUZ FILHO, I. J. da; FERREIRA, H. K. L.; SILVA, S. K. G. da; MACHADO, S. E. F.; ZAIDAN, L. E. M. C.; LIMA, V. F. de; MARQUES, O. M.; NASCIMENTO JÚNIOR, A. J. do. Otimização do processo de remoção do corante preto de remazol B por uso de biomassa mista de Aspergillus niger van Tieghem, 1867 (Ascomycota: Trichocomaceae) e Pennisetum purpureum Schumach., 1827 (Poales: Poaceae). Revista Brasileira de Gestão Ambiental e Sustentabilidade, v. 3, n. 6, p. 375-384, 2016. http://dx.doi.org/10.21438/rbgas.030611 CRUZ, I. J. da; MARQUES, L. M.; SOUZA, K. C.; LIMA, V. F. de; MARQUES, O. M.; NASCIMENTO JÚNIOR, A. J. do. Remoção do corante Remazol Black b pelo uso da biomassa mista de Aspergillus niger e capim elefante (Pennisetum purpureum schum). Engevista, v. 18, n. 2, p. 265-279, 2016. https://doi.org/10.22409/engevista.v18i2.727 CUNICO, P.; KUMAR, A.; FUNGARO, D. A. Adsorption of Dyes from Simulated Textile Wastewater onto Modified Nanozeolite from Coal Fly Ash. Journal of Nanoscience and Nanoengineering, v. 1, n. 3, 2015. DAWODU, M. O.; AKPOMIE, K. G. Evaluating the potential of a Nigerian soil as an adsorbent for tartrazine dye: Isotherm, kinetic and thermodynamic studies. Alexandria Engineering Journal, v. 55, n. 4, 2016. https://doi.org/10.1016/j.aej.2016.08.008 EL BOURAIE, M.; EL DIN, W. S. Biodegradation of Reactive Black 5 by Aeromonas hydrophila strain isolated from dye-contaminated textile wastewater. Sustainable Environment Research, v. 26, n. 5, 2016. https://doi.org/10.1016/j.serj.2016.04.014 ELMOUBARKI, R.; MAHJOUBI, F. Z.; TOUNSADI, H.; MOUSTADRAF, J.; ABDENNOUR, M.; ZOUHRI, A.; ALBANI, A. El.; BARKA, N. Adsorption of textile dyes on raw and decanted Moroccan clays: Kinetics, equilibrium and thermodynamics. Water Resources And Industry, v. 9, 2015. https://doi.org/10.1016/j.wri.2014.11.001 EMBRAPA. Manual de Métodos de Análise de Solo. 2. ed. Rio de Janeiro: Embrapa-cnps, 1997. 212 p. Rev. Ambient. Água vol. 15 n. 2, e2491 - Taubaté 2020 Sorption of Remazol Black B dye in … 11 ERRAIS, E.; DUPLAY, J.; ELHABIRI, M.; KHODJA, M.; OCAMPO, R.; BALTENWECK- GUYOT, R.; DARRAGI, F. Anionic RR120 dye adsorption onto raw clay: Surface properties and adsorption mechanism. Colloids And Surfaces A: Physicochemical and Engineering Aspects, v. 403, 2012. https://doi.org/10.1016/j.colsurfa.2012.03.057 FELISTA, M. M.; WANYONYI, W. C.; GILBERT, O. Adsorption of Anionic Dye (Reactive Black 5) Using Macadamia Seed Husks: Kinetics and Equilibrium Studies. Scientific African, in press, 2020. https://doi.org/10.1016/j.sciaf.2020.e00283 FREUNDLICH, H.; HELLER, W. The Adsorption ofcis- and trans-Azobenzene. Journal of the American Chemical Society, v. 61, n. 8, 1939. GAVRILESCU, M. Fate of Pesticides in the Environment and its Bioremediation. Engineering In Life Sciences, v. 5, n. 6, 2005. https://doi.org/10.1002/elsc.200520098 HO, Y. S.; MCKAY, G. Pseudo-second order model for sorption processes. Process Biochemistry, v. 34, n. 5, 1999. https://doi.org/10.1016/S0032-9592(98)00112-5 HUYNH, N.; CHIEN, C. A hybrid multi-subpopulation genetic algorithm for textile batch dyeing scheduling and an empirical study. Computers & Industrial Engineering, v. 125, 2018. https://doi.org/10.1016/j.cie.2018.01.005 JAYANTHY, V.; GEETHA, R.; RAJENDRAN, R.; PRABHAVATHI, P.; SUNDARAM, S. K.; KUMAR, S, D.; SANTHANAM, P. Phytoremediation of dye contaminated soil by Leucaena leucocephala (subabul) seed and growth assessment of Vigna radiata in the remediated soil. Saudi Journal Of Biological Sciences, v. 21, n. 4, 2014. https://doi.org/10.1016/j.sjbs.2013.12.001 JIANG, S.; YU, T.; XIA, R.; WANG, X.; GAO, M. Realization of super high adsorption capability of 2D δ-MnO2 /GO through intra-particle diffusion. Materials Chemistry and Physics, v. 232, p.374-381, 2019. https://doi.org/10.1016/j.matchemphys.2019.05.004 KETELSEN, H.; MEYER-WINDEL, S. Adsorption of brilliant blue FCF by soils. Geoderma, v. 90, n. 1-2, 1999. https://doi.org/10.1016/S0016-7061(98)00119-0 KHARAT, D. S. Treatment of textile industry effluents: limitations and scope. Journal of Environmental Research and Development, v. 9, n. 4, 2015. LAGERGREN, S. About the theory of so-called adsorption dissolved substances. Kungliga Svenska Vetenskapsakademiens Handlingar, v. 24, n. 4, 1898. LAZARIDIS, N. K.; KEENAN, H. E. Chitosan beads as barriers to the transport of azo dye in soil columns. Journal of Hazardous Materials, v. 173, n. 1-3, 2010. https://doi.org/10.1016/j.jhazmat.2009.08.062 LIU, R.; LIU, X.; TANG, H.; SU, Y. Sorption Behavior of Dye Compounds onto Natural Sediment of Qinghe River. Journal of Colloid and Interface Science, v. 239, n. 2, 2001. MARTINS, J. M. F.; MERMOUD, A. Transport of rimsulfuron and its metabolites in soil columns. Chemosphere, v. 38, n. 3, 1999. https://doi.org/10.1006/jcis.2001.7597 PEKAKIS, P. A.; XEKOUKOULOTAKIS, N. P.; MANTZAVINOS, D. Treatment of textile dyehouse wastewater by TiO2 photocatalysis. Water Research, v. 40, n. 6, p.1276-1286, 2006. https://doi.org/10.1016/j.watres.2006.01.019 Rev. Ambient. Água vol. 15 n. 2, e2491 - Taubaté 2020 12 Adriana Thays Araújo Alves et al. PEREIRA, L. de O.; MOURA, S. G. de.; COELHO, G. C. M.; OLIVEIRA, L. C. A.; ALMEIDA, E. T. de; MAGALHÃES, F. Magnetic photocatalysts from industrial residues and TiO2 for the degradation of organic contaminants. Journal of Environmental Chemical Engineering, v. 7, n. 1, p.1-12, 2019. https://doi.org/10.1016/j.jece.2018.102826 QU, B.; ZHOU, J.; XIANG, X.; ZHENG, C.; ZHAO, H.; ZHOU X. Adsorption behavior of Azo Dye C. I. Acid Red 14 in aqueous solution on surface soils. Journal of Environmental Sciences, v. 20, n. 6, 2008. https://doi.org/10.1016/S1001- 0742(08)62116-6 RABELO, A. E. C. G. C. Retenção e mobilidade da sulfadiazina em um aluvionar do Alto do Capibaribe. 2018. 76 p. Dissertação (Mestrado em Tecnologias Energéticas e Nucleares) - Universidade Federal de Pernambuco, Recife, 2018. SANA, D.; JALILA, S. Combined effect of unsaturated soil condition and soil heterogeneity on methylene blue adsorption/desorption and transport in fixed bed column: Experimental and modeling analysis. Journal of King Saud University – Science, v. 28, n. 4, 2016. https://doi.org/10.1016/j.jksus.2016.01.004 SEBRAE. Estudo econômico do arranjo produtivo local de confecções do Agreste Pernambucano. Recife, 2013. 151 p. SHALABY, N. H.; EWAIS, E. M. M.; ELSAADANY, R. M; AHMED, A. Rice husk templated water treatment sludge as low cost dye and metal adsorbent. Egyptian Journal of Petroleum, v. 26, n. 3, 2017. https://doi.org/10.1016/j.ejpe.2016.10.006 SMARANDA, C.; GAVRILESCU, M.; BULGARIU, D. Studies on Sorption of Congo Red from Aqueous Solution onto Soil. International Journal of Environmental Research, v. 5, n. 1, 2011. https://dx.doi.org/10.22059/ijer.2010.303 SMARANDA, C.; POPESCU, M. C.; BULGARIU, D.; MĂLUŢAN, T.; GAVRILESCU, M. Adsorption of organic pollutants onto a Romanian soil: Column dynamics and transport. Process Safety and Environmental Protection, v. 108, 2017. https://doi.org/10.1016/j.psep.2016.06.027 SOUZA, S. M. de A. G. U. de; BONILLA, K. A. S.; SOUZA, A. A. U. de. Removal of COD and color from hydrolyzed textile azo dye by combined ozonation and biological treatment. Journal of Hazardous Materials, v. 179, n. 1-3, p. 35-42, 2010. https://doi.org/10.1016/j.jhazmat.2010.02.053 STAGNARO, S. M.; VOLZONE, C.; HUCK, L. Nanoclay as Adsorbent: Evaluation for Removing Dyes Used in the Textile Industry. Procedia Materials Science, v. 8, 2015. https://doi.org/10.1016/j.mspro.2015.04.112 WEBER, W. J.; MORRIS, J. C. Kinetics of adsorption on carbon from solution. Journal of Sanitary Engineering, Division ASCE, v. 89, n. 2, 1963. WEI, Z.; YAN, X.; LU, Z.; WU, J. Phosphorus sorption characteristics and related properties in urban soils in southeast China. Catena, v. 175, 2019. https://doi.org/10.1016/j.catena.2018.12.034 Rev. Ambient. Água vol. 15 n. 2, e2491 - Taubaté 2020 Ambiente & Água - An Interdisciplinary Journal of Applied Science ISSN 1980-993X – doi:10.4136/1980-993X www.ambi-agua.net E-mail: [email protected] On characteristic hydraulic times through hydrodynamic modelling: discussion and application in Patos Lagoon (RS) ARTICLES doi:10.4136/ambi-agua.2456 Received: 19 Aug. 2019; Accepted: 12 Feb. 2020 Laura Aguilera* ; Ana Lígia Favaro Dos Santos ; Paulo Cesar Colonna Rosman Área de Engenharia Costeira. Programa de Engenharia Oceânica. Instituto Alberto Luis Coimbra de Pós Graduação de Engenharia. Universidade Federal do Rio de Janeiro (UFRJ), Centro de Tecnologia, Bloco C, S/N, CEP: 21941-972, Rio de Janeiro, RJ, Brazil. E-mail: [email protected], [email protected] *Corresponding author. E-mail: [email protected] ABSTRACT Although the analyses of characteristic hydraulic times are important diagnostic tools for studying water mass exchanges and identifying areas prone to stagnation that are potentially subjected to eutrophication effects, their concepts and uses are often misinterpreted. This paper compares similarities and differences between widely used characteristic hydraulic times, CHT, known as Residence Time, Times of Water Renewal Rates and Water Age. A proper definition for each of these characteristic hydraulic times is stated to avoid the existing confusion with multiple concepts in the literature. Methodologies to compute these CHT through hydrodynamic modelling systems are presented and, in order to enhance understanding, applied to three idealized cases in steady flow channels: (1) Channel with uniform flow; (2) Channel with a lateral inflow; and (3) Channel with a lateral embayment. Finally, a practical example is discussed by applying the methodologies to the Patos Lagoon (RS). The results for the idealized channel cases are non-intuitive and this theoretical discussion clarifies the interpretation and uses of different timescales and outlines the Water Age as the more versatile and multifunctional timescale if compared to the others addressed here. The results for the Patos Lagoon exemplify the valuable information that CHT can offer for environmental management in natural water bodies. Keywords: environmental hydrodynamics, hydrodynamic modelling, transport timescales. Sobre tempos hidráulicos característicos através de modelagem hidrodinâmica computacional: discussão e aplicação à Lagoa dos Patos (RS) RESUMO Embora a análise de tempos hidráulicos característicos seja uma ferramenta importante para estudar trocas de massas de água e identificar áreas propensas a estagnação de águas, que são potencialmente vulneráveis a efeitos de eutrofização, seus conceitos e usos são interpretados de forma errada com frequência. Este artigo compara as diferenças e similaridades entre tempos hidráulicos característicos, CHT, amplamente utilizados, tais como: Tempo de Residência, Tempo de Taxas de Renovação e Idade da Água. Definições precisas de cada um This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 Laura Aguilera et al. destes tempos característicos são incluídas neste trabalho com o intuito de evitar confusão entre os múltiplos conceitos presentes na literatura. São apresentadas metodologias para o cálculo destes CHT utilizando sistemas de modelagem hidrodinâmica e, a fim de aprimorar o entendimento, aplicadas a três casos idealizados em canais de fluxo constante: (1) Canal com fluxo uniforme; (2) canal com um afluxo lateral; (3) Canal com uma baia lateral. Posteriormente, um exemplo prático é discutido aplicando as metodologias à Lagoa dos Patos (RS). Os resultados para os casos de canais idealizados não são intuitivos. A discussão teórica esclarece a interpretação e os usos dos diferentes tempos característicos e destaca a Idade da Água como o mais versátil e multifuncional, se comparada com os outros CHT abordados neste trabalho. Os resultados da Lagoa dos Patos são um exemplo do grande valor das informações que os CHT oferecem para a gestão ambiental em corpos hídricos naturais. Palavras-chave: hidrodinâmica ambiental, modelagem hidrodinâmica, tempos hidráulicos característicos. 1. INTRODUCTION The analysis of characteristic hydraulic times (CHT) has been used as an important diagnostic tool. These analyses are helpful to track the water mass exchange (Monsen et al., 2002), giving us an important knowledge of the hydrodynamics processes that helps water bodies to recover from local pollution. Currently, transport models are the main tool used worldwide to develop CHT analysis (Bacher et al., 2016). One can find numerous examples in the literature of CHT studies on water bodies pressured by the surrounding population or by the presence of industrial activity, that usually present environmental risks. Du and Shen (2016) studied the Residence Time in the Chesapeake Bay, the largest estuary in the United States and very important for local economy and ecology. Also, Ying et al. (2018) and Qi et al. (2016) used CHT to study, respectively, the quality of water in deteriorated bays due to anthropogenic influences and deteriorated lakes that face an eutrophication problem. Water timescales analysis has been also developed in important lagoons like the Lagoon of Venice in the northeast of Italy (Viero and Defina, 2016), or reservoirs like Jirau Reservoir which shelters the Jirau hydropower system (Rosman, 2018), on Madeira River in the Brazilian Amazon Region. Port zones have also been investigated using CHT, assisting in harbor environmental management as stated by Grifoll et al. (2014), where the authors analyzed the water renewal and mixing of the Barcelona harbor zone in the northwest Mediterranean Sea. Despite the extensive use of CHT analysis, there is no consensus in definitions, concepts and methodologies. As a result, several definitions of characteristic hydraulic timescales have been published (Bolin and Rodhe, 1973; Zimmerman, 1976; Monsen et al., 2002; Delhez et al., 2014; Cucco and Umgiesser, 2015; Liu et al., 2017; Huguet et al., 2019). There are several concepts that are different from each other but are closely related between them, thus very precise definitions are necessary to obtain correct result interpretations. The purpose of this study is to contribute towards a consensus for concepts and methodologies to calculate CHT and discuss correct interpretations of the results to stimulate their applications in complex natural water bodies using hydrodynamic computational models. The specific objectives were: (1) compare transport time scales widely used to measure water retention and scalar quantities transported with water, focusing on the similarities and differences between the concepts of Residence Time, Times of Renewal Rates and Water Age; (2) describe and present clearly and accurately the procedures for computing these concepts; (3) calculate Residence Time, Times of Renewal Rates and Water Age applied to idealized cases to identify the influence of inflows and stagnation water areas in these CHT; (4) calculate Residence Time, Times of Renewal Rates and Water Age in a natural water body, specifically Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 On characteristic hydraulic times through hydrodynamic modelling … 3 in the Patos Lagoon (RS); and (5) identify challenges in analyzing results of Residence Time, Times of Renewal Rates and Water Age in natural water bodies. It is important to clarify that the objective of presenting CHT results in Patos Lagoon is to discuss correct interpretation of the results for natural water bodies. 2. MATERIALS AND METHODS We adopted in this work the following definitions: a) Residence Time (RT): given a domain of interest in a water body with particles positioned at various locations in an initial time, the RT for each particle is the time it takes to leave the specified domain as it is passively transported by local currents; b) Times of Renewal Rates (TRR%) represents the time it takes to attain a water renewal of X% in different regions of the water body; and, c) the Water Age (WA) indicates, for a given position of the domain, the average time the water parcels that are in that position remain in the domain of interest as the flow circulates through the domain. The mathematical models for Residence Time, Times of Renewal Rates and Water Age hereby presented were implemented and applied to three idealized channel cases and a natural water body using SisBaHiA®, a professional well-tested computational system for hydrodynamic modelling registered by COPPE/UFRJ, http://www.sisbahia.coppe.ufrj.br/. This computational system has been successfully used in different projects and scientific research (González-Gorbeña et al., 2015; Peixoto et al., 2017; Rosman, 2018; Silva et al., 2019). Nevertheless, the following methodologies are not restricted to be used with SisBaHiA®, and can be implemented in any other hydrodynamic numerical model. In this work, the following SisBaHiA® models were adopted for numerical simulations: the Eulerian Transport Model (ETM) to calculate the TRR% and the WA; and the Lagrangian Transport Model (LTM) to calculate the RT. All transport models were driven by hydrodynamic models included in SisBaHiA®. The governing equations for such model adopt a filtering technique approach similar to Large Eddy Simulation to define turbulence stresses (Bedford and Dakhoul, 1982; Smagorinsky, 1963; Leonard, 1975; Aldama, 1985; Rosman, 1987). The spatial discretization is optimized for natural water bodies and uses mostly biquadratic quadrilateral finite elements with nine nodes but can also include quadratic triangular finite elements with six nodes. The spatial discretization is up to fourth order, depending on the mesh irregularity. The temporal discretization uses second order implicit finite differences scheme, mixing Crank-Nicolson (Crank and Nicolson, 1947) and Implicit Factored schemes (Beam and Warming, 1978). The SisBaHiA® ETM and LTM solve the advective-diffusive transport processes with kinetic reactions and adopt filtering techniques to define turbulent diffusivities. The ETM is suitable to simulate the scalar transport of dissolved substances in the water column, like generic substances, contaminants or any order parameter that indicates water quality. The LTM is ideal to simulate the scalar transport of substances that are floating, mixed or occupying only one layer in the water column. Therefore, the LTM model is capable of simulating small-scale clouds of contaminants and plumes. Ample details of SisBaHiA® models, equations and numerical schemes are in Rosman (2019). All the simulations carried out in this paper used the Hydrodynamic 2DH Model, where the quantity conservation equations motion and the continuity equation are vertically averaged. 2.1. Residence Time Simulation The most common characteristic hydraulic time is the Residence Time (RT). However, this is a term that has different meanings depending on the scientific community or work. The application of computational modelling allows the definition of the RT as a function varying in space for different hydrodynamic conditions. Although there are many concepts applied to the RT terminology, most of them considered it as the required time for a particle to traverse a given Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 4 Laura Aguilera et al. domain (Zimmerman, 1976; Monsen et al., 2002; Delhez et al., 2014; Du and Shen, 2016). Bacher et al. (2016) presented a review of articles that use hydrodynamic modelling to calculate Residence Time with lagrangian and eulerian approaches. Here, to calculate the RT within a predefined region of the modelling domain, the LTM receives information directly from the hydrodynamic model. Initially, the predefined domain is filled with neutral particles. The particles represent centroids of water mass parcels inside the domain and therefore, they do not occupy space. The model enumerates and associates every particle with its initial position and release instant. The LTM of RT considers advective and dispersive processes of particles but does not compute turbulent diffusion of water masses among particles. The total simulation time is defined to characterize the period of interest, during which the local currents transport all the particles. Whenever a particle exits the predefined domain, its RT is recorded in its launch position. Hence, at the end of the simulation, the value of the RT of each particle is registered at the launching position of the particle inside the predefined domain. Particles that remained within the domain until the end of the simulation receive an RT equal to the duration of the simulation. 2.2. Times of Renewal Rates Simulation For heterogeneous and varied water bodies, it is better to use the eulerian approach, which permits the analyses of parcels of water at different locations over time. In this approach, the water flux passes through a control volume that is considered an observation point. For this reason, if the goal is to analyze the characteristic time for water renewal, it is recommended that the Times of Renewal Rates (TRR%) be computed directly at different points over time, to obtain the time evolution of the renewal rates at different points of the study domain (Roversi et al., 2016; Rosman, 2018). Following the usual hierarchy of the models, an ETM that calculates TRR% receives information directly from a hydrodynamic model. The TRR% simulation assumes a reference value of Water Renewal Rate, WRR, equal to 0% for the waters that are inside the domain of interest at the initial simulation instant. For renewal purposes, incoming waters, i.e., waters that enter the domain by the open boundaries or through other inflows, such as rivers, have a reference value equal to 100%. As new water with 100% reference value mixes with initial water of 0% reference value an intermediary value is computed, indicating the percentage of mixing at any given point in time. To represent these two conditions, a generic substance with concentration C is used as a tracer for new water. Consequently, at the beginning of the simulation, all the water enclosed within the domain of interest is considered old and is prescribed with concentration C = 0. All new water inflows in the domain after the initial time are considered new water with concentration C = 100. Then, due to the advection, dispersion and diffusive processes, the percentage of fresh or new water in the domain will be directly proportional to this generic substance concentration, varying from 0% to 100%. The values resulting from these simulations represent the percentage of the mixing of new and old waters in each position of interest, delimited by the predefined domain. The WRR will be different at each point of the domain because it depends on the magnitudes of the currents and turbulence in different places and times, as a function of the advective-diffusive transport. The Times of Renewal Rates, TRR%, are the characteristic hydraulic times associated with the concept of water renewal. It means the necessary time, with respect to the initial modelling time, for a water parcel to reach a specific value of Water Renewal Rate, WRR. 2.3. Water Age Simulation The Water Age is an extended and very discussed concept in literature with different Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 On characteristic hydraulic times through hydrodynamic modelling … 5 methodologies (Deleersnijder et al., 2001; Li and Shen, 2015; Qi et al., 2016; Viero and Defina, 2016; Huguet et al., 2019). Here, the analysis of Water Age allows us to analyze the average time that the water remains in the predefined domain over time. This time is estimated from the decay of an age-marker passive substance present in water. To determine the decay time, a first order decay kinetic reaction of the age-marker substance is mandatory, with a constant rate of k > 0 and without other effects of losses and gains of mass. To conceptualize the calculation, consider a uniform well-mixed volume of water in the whole domain, with initial concentration C0 for the age-marker substance. Considering a first- order decay kinetics, the time variation of the concentration of the age-marker substance, C (t), is given by Equation 1: 푑퐶 = −푘퐶 (1) 푑푡 Whose analytical solution leads to Equation 2: 퐶(푡) = 퐶0 exp(−푘푡) (2) and hence Equation 3: 퐶 −푙푛( ) 푡 = 퐶0 (3) 푘 Once the initial concentration C0 and a later concentration C (t) are known, the decay time elapsed between the two concentration values defines the WA at the recorded time of C (t), in respect to the initial condition. The k unit is the inverse of time and it is easier to understand its magnitude by an equivalent time, like the well-known half-life time denoted as T50. For example, it is more intuitive to understand that every two days a given concentration will be reduced by 50% than to extract 푙푛(0.5) this information from a reaction rate of k = -0.347/day. Note that 푇 = − . Another very 50 푘 useful equivalent time is T90, which is the time it takes for a 90% concentration reduction due to decay processes. Note that T90 is equivalent to an order of magnitude decay, thence ln(0.1) 푘 = − . 푇90 When considering a water body in which new water with C = C0 inflows in multiple points at different times and outflows of water with different decay periods might occur at different points and times, it becomes evident that the C will be a function of space and time. Therefore, the WA will also be a function varying in space and time. Hence, at a given position and instant, due to turbulent advective-diffusive transport mechanisms, the WA function value represents an average age for the local water mixture, which is composed of water parcels with different ages, given by Equation 4: 퐶(푥,푦,푡) − ln( ) 푊 (푥, 푦, 푡) = 퐶0 (4) 퐴 푘 Regarding the decay kinetics, the value of WA does not depend on the value of the decay rate k, because the resulting values of C are consonant with k. However, in natural water bodies, with space-time varying flows, different values of k will cause different concentration gradients. In the mass balance equation for the decaying age-marker substance, the turbulent advective- diffusive balancing fluxes depend on the concentration gradients, and due to that, the resulting WA can differ slightly for different values of the decay rate. For this reason, it is important to prescribe a suitable k value to obtain proper results for water age function WA (x, y, t). Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 6 Laura Aguilera et al. As the numerical accuracy is limited, the decay constant k must be carefully chosen in terms of the equivalent T90. For every elapsed T90 in a simulation, a decay of one order of magnitude occurs, which involves a decimal place. If T90 is too large in relation to the duration of the modelling, the decay may be so small that the values of C will be always very close to C0. On the other hand, if the given T90 is too small in relation to the duration of the modelling, the values of C will approach zero rapidly, the gradients of C will be more pronounced near the inputs and the effects of advective-diffusive balancing fluxes terms will have more influence on the estimation of WA. Both cases may generate inaccuracy. For best results, suitable values of k should have an equivalent T90 between half and double the duration of the simulation. ® To calculate the WA with SisBaHiA , the ETM receives information directly from a hydrodynamic model. A primary initial condition C (x, y, t0) = C0 = 1 is set throughout the domain. Therefore, at the beginning WA= 0, since ln (1) = 0 in all locations. During the simulation time, the new waters that enter the domain by the open boundaries or through other inflows, such as rivers, have age zero and, therefore, must have age-marker substance concentration equal to one, i.e., C (xi, yi, t) = C = 1. As the initial waters and the new waters with WA= 0 are mixed and transported in the system domain, the value of C decreases at each point as a function of the decay process. Thus, the value of WA becomes different at each point because it depends on the magnitude of the currents and the turbulence at each location during the simulation time. An important consideration about the hydrodynamic models linked with transport models for the analysis of Water Age is that precipitation and evaporation should not be included. These two processes produce a change in the water volume and can lead to distortions in the result of Water Age due to dilution or intensification of the concentration of the age-marker substance used to calculate WA. In natural systems where it is necessary to include these effects, such as lakes, for example, equivalent lateral flows could be used to incorporate the mass of the reference substance, or infiltration and exfiltration processes. The total simulation time to analyze Water Age should be enough for the simulation to achieve a dynamic equilibrium. An appropriate duration should be approximately the time required for a renewal of at least 50% of the water of the system that is being modelled. This duration can be estimated doing a previous modelling of TRR%. 2.4. Study Cases For the idealized tests, three processes were approached using steady flow situations: (a) water exchanges in a uniform channel; (b) the effect of lateral inflows; and (c) the effect of water stagnation areas. Therefore, to analyze CHT for these cases, three numerical steady flow tests were developed: Test 1 - Channel with uniform flow; Test 2 – Channel with a lateral inflow; and, Test 3 – Channel with a lateral embayment, to represent a stagnant prone zone. The simple geometry of all tests allows an easy and intuitive interpretation of the results, facilitating the observation of the influence of each variable and, in this case, the physical result of water renewal using the concepts of Residence Time, Times of Renewal Rates and Water Age. All tests employed similar computational domain and mesh discretization, with changes only to include a lateral inflow in Test 2 and a lateral embayment in Test 3. Next sections describe the characteristics of each test, which were modelled using SisBaHiA®. For all tests, the respective channel has an equivalent bottom roughness amplitude of ½ 0.02m, which results in Chézy coefficient values 퐶ℎ ≅ 50m /s. Test 1. Channel with uniform flow This test considers a straight channel with 10km extension and 600m width. The initial conditions were a predefined water level gradient and homogeneous water column, H = 2m. At Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 On characteristic hydraulic times through hydrodynamic modelling … 7 3 the upstream boundary, there is an inflow of Q1=300m /s uniformly distributed, and at the downstream boundary the water level is given as –0.125m. The channel’s bathymetry has a slope to result in a uniform and steady flow in the channel, with a depth averaged velocity of 0.25m/s. Figure 1 schematizes Test 1, whose domain was discretized with a quadratic finite element mesh with 300 quadrilateral elements of 200m × 100m, v. Figure 2. Figure 1. Idealized modelled channel scheme for Test 1. Figure 2. Left: Modelling domain of the channel for Test 1 to Test 3 with the finite element mesh, bathymetry, and the position of Station A used to present the results. Axes represent local coordinates in metres. In the figure, the elements are shown with internal lines connecting the 9 nodes of each element. Right: Modelling domain of Patos Lagoon with the finite element mesh, bathymetry, and the position of stations A-B used to present the results. Axis in UTM coordinates (WGS84, 22S). Test 2. Channel with a lateral inflow Test 2 was carried out with the same modelling domain and the same initial conditions 3 used in Test 1. To simulate a lateral inflow on the mainstream, a constant inflow of Q2=200m /s was introduced in the center of the left margin of the channel, as shown in Figure 2. The resulting velocity field for this test is steady and varied along the channel. Test 3. Channel with a lateral embayment Test 3 considers the same channel with a 10km extension and a 600m width but has a lateral embayment in the center of the channel, with a width of 600m and a length of 1000m. Figure 2 presents the discretized domain, with a quadratic mesh of 336 quadrilateral finite elements of 200m × 100m. The initial conditions were the same as those established in Test 1, with a constant and spatially distributed discharge of Q1=300m³/s upstream, the water level Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 8 Laura Aguilera et al. fixed at –0.125m at the downstream boundary. The resulting velocity field is steady and varied along the channel. For all the idealized tests, the total simulation time was 24h. For Test 1, the travel time along the channel is approximately 11h but the total simulation time was extended to 24h because Test 3 requires even longer to fully renovate. It is worth mentioning that for all the idealized tests the time step of the hydrodynamic model was 60s, with a maximum Courant number of 6.5. To compute the RT with the LTM for all the idealized tests, the entire domain was filled with neutral particles one-metre apart from each other. Patos Lagoon study case Patos Lagoon is located in the state of Rio Grande do Sul, Brazil, and extends from latitudes 29.99° S to 32.20° S with mean longitude of 51.40° W, Figure 3. It is the largest choked coastal lagoon in the world (Kjerfve, 1986), with over 300km in length and an average width of 40km, its surface covers about 10360km2. The lagoon receives waters from an approximately 200000km2 drainage basin (Seeliger et al., 1997). Socioeconomic activities such as agriculture and extensive livestock farming have been developed around the lagoon (Fernandes, 2001). Figure 3. Localization and satellite view of Patos Lagoon (Lansat 8 OLI, 2016). The Lagoon is connected to the ocean through a channel located at its southern end, the Rio Grande Channel (Marques et al., 2009). The Port of Rio Grande, the second most important port in Brazil for the development of Brazilian international trade (Rio Grande do Sul, 2019), is near the mouth of the lagoon at the Atlantic Ocean. Patos Lagoon is navigable by vessels from the mouth to Guaíba Lake, northwest of the lagoon (Martelo et al., 2019). The so-called Guaíba Lake is the main source of fresh water supply to the metropolitan area of Porto Alegre, the State capital, with a population of about 4.3 million inhabitants (Bendati et al., 2000). Studies of hydraulic timescales could characterize areas prone to stagnation and indicate critical measurement points for quality monitoring programs. The delimitation of zones whose waters are mostly renewed by riverine or tidal flows are some of the relevant results that could be extracted from the modelling of CHT in Patos Lagoon. Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 On characteristic hydraulic times through hydrodynamic modelling … 9 The computation of CHT to Patos Lagoon serves as a guide for applications and results interpretations for other studies. Patos Lagoon was chosen to compute CHT for the following reasons: ● Seasonal changes significantly modify its hydrodynamic circulation, due to changing winds, river discharges and storm surges; ● It has a connection with the sea and, therefore, a tidal influence area; ● There are important economic and industrial activities in its basin; ● In terms of CHT, there are just a few studies related to Residence Time of the lagoon, in a traditional way, which differs significantly from what we present ahead (Moller, 1996; Fernandes, 2001). The adopted modelling domain of Patos Lagoon, shown in Figure 2, and the hydrodynamic model for the Patos Lagoon is the same as that which was calibrated and validated for the hydro- sedimentological analysis concerning the National Dredging Plan of the National Secretary of Ports, of the Brazilian Federal Government (COPPETEC, 2015). The modelling domain of Patos Lagoon includes all the lagoon and vicinal coastal areas. It has a variable depth distribution, with an average of 6m, making the lagoon a very shallow water body, tending to be vertically well-mixed. The entrance channel is about 22km long, 2km wide and approximately 12m deep. The main port terminals are in this channel, in which the water column can be vertically stratified by saline intrusion. Bathymetry data, derives from nautical charts of the Directorate of Hydrography and Navigation of the Brazilian Navy, and other available data from surveys in the channels, and it is referred to mean sea level at Rio Grande Port. The sediment characterization of the Patos Lagoon and the most distant areas of the navigation channels is predominantly silty, with fractions of sand and clay (Toldo Jr. et al., 2005). In the port areas, available sediment data from surveys were used (DNIT, 2007; FURG, 2008). The discretization of the domain used 1982 quadratic finite elements, containing 8149 calculation nodes. In Figure 2, the mesh grid is shown with internal lines connecting the 9 nodes of each quadrangular element and the 6 nodes of each triangular element. For a better characterization of the hydrodynamics and water renewal, this study considers two seasonal scenarios: a Summer/Dry scenario and a Winter/Wet scenario, from 12/21/2010 to 03/20/2011 and 06/21/2011 to 09/23/2011, respectively. For both scenarios, the modelling includes effects of astronomical tides and storm surges, the main tributary rivers and local winds. Due to the importance of waves generated by local winds in Patos Lagoon, the hydrodynamic model was coupled with the wave generation model . Storm surge effects in the mean water level were obtained from averaging daily measurements. The astronomical tide levels, generated from the main harmonic constants of a tidal station, were also considered despite their minor influence on the hydrodynamic regime. Both stations were located at the end of the Rio Grande Channel. The NCEP Reanalysis Model (Kistler et al., 2002) provided the wind data used in this modelling, for 25 points distributed along the modelling area at a resolution of 0.5º. For the period covered, the northeast quadrant winds are predominant, and the highest velocities were 16m/s. When cold fronts hit the study area, winds of the southwest quadrant were observed. These events generate a set-up and set-down mechanism of oscillation with the nodal line in the mid lagoon area. This oscillation has the same period of the passages of frontal systems for this region, 3 to 10 days, which occurs more frequently in winter. Figure 4 shows the sea level boundary condition and the wind regime for the two scenarios. The modelling considers the inflows of the three main tributaries: daily flow data from ANA (2015) for Jacuí River and Camaquã River, and a mean annual value for São Gonçalo Channel (Bordas et al., 1984; Hartman and Harkot, 1990; Vaz et al., 2006). Jacuí River is the Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 10 Laura Aguilera et al. river with higher discharge seasonal changes; it has a maximum discharge approximately of 1600m3/s for the Dry scenario and 16000m3/s for the Wet scenario. For the simulation of CHT in Patos Lagoon, the total simulation time was 3 months for each scenario, the time step of the hydrodynamic model was 100s, with a maximum Courant number of 26. To compute the RT with the LTM for the Patos Lagoon simulation, the entire domain was filled with around 13100 neutral particles, no more than 1000m apart. Figure 4. Sea level boundary condition and wind regime for Dry and Wet Season scenarios. 3. RESULTS AND DISCUSSION 3.1. Residence Time Figure 5 shows the isolines maps for the three idealized tests at the end of the RT simulation. At the end of the simulation, the particles that have not left the channel have a RT value of 24h. As it can be seen, the RT presents different values along the channel. For all cases, as expected, next to the open boundary the water RT is minimum. For Test 1 and Test 2, the Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 On characteristic hydraulic times through hydrodynamic modelling … 11 water in the upstream of the channel has the maximum RT. For Test 3 the maximum RT is within the lateral stagnant embayment. Comparing Test 1 and Test 2, the influence of the lateral inflow is noticeable. The lateral inflow imparts a faster flow in the downstream half of the channel, resulting in a RT lower at such half of the channel in Test 2 if compared to Test 1. The lateral inflow creates a backwater upstream of the confluence, which hinders the flow, making the RT higher in the upstream half of the channel if compared to Test 1. This is a relevant aspect, because when planning a monitoring campaign, it is important to consider relevant inflows entering the mainstream. Figure 5. Above: Maps of isolines of Residence Time, for the end of the 24h simulation for Test 1 to Test 3. Below: Maps of isolines of Residence Time for the end of the three-month simulation for the Dry and Wet scenarios in Patos Lagoon. In Test 3, the left margin upstream of the lateral embayment presents values of RT higher than the right. This happens because particles flowing in the left margin are tapped in the lateral embayment. These particles are retained in the stagnation area and require more time to leave the channel. In the lateral embayment yet, particles remain trapped in this region during the 24h of simulation, so the RT = 24h. The RT analysis shows that stagnation areas in relatively low flows, like the one presented in the idealized channel, can confine water. In nature, this represents regions with low water renovation that are prone to trophic processes. In the case of Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 12 Laura Aguilera et al. Test 3, results showed particles retained at the stagnation area during the whole simulation time. This is not a completely realistic situation compared with eddy areas in natural flows, where diffusive processes would cause mixing with water parcels outside of the eddy area. The results of Patos Lagoon in Figure 5, at the final time of the RT simulation for the Dry and Wet season scenarios, show that the particles that did not exit the lagoon after the 90-day simulation period got a RT value of 90 days. For both scenarios, the northern region has a higher RT than the rest of the lagoon, but the isolines maps show relevant seasonal differences. For the Dry scenario, all the particles that were at the initial time in the north region do not leave the lagoon after 90 days. For the Wet scenario, the RT value decreases from 90 days to approximately 70 days in the northwest region. As stated in the idealized channel Test 2, river discharge is not represented in RT simulations as new water entering the modelling domain. Although, the influence of significantly higher values of Jacuí River discharges during the wet season are noticeable. The stronger velocities induced by Jacuí River allow the particles of the northwest region to reach the middle lagoon area. In the middle of the lagoon, the influence of frontal systems forces the entrance of sea water, increasing the magnitude of the velocities and allowing the particles located in the southern areas to exit the lagoon through the Rio Grande Channel. Smaller river discharges that have no relevant influence on the hydrodynamics, such as the Camaquã River, do not influence significantly the final result of RT. Tidal influence is observed comparing the Dry and Wet RT results in the saline intrusion area. For Dry scenario, when river discharges of Jacuí River are smaller, tidal entrance is not restrained and the isolines of RT < 20 days are located in a more internal zone of the lagoon. The preferential flow course is on the right of Rio Grande Channel and, consequently, the RT of the little estuarine arms located at the left of the channel is higher. For the Wet scenario, Jacuí higher discharges imply stronger opposition to tidal entrance and, therefore, values of RT < 20 days are limited to a narrower estuarine area. In this scenario, the difficulty of tidal flow to enter the lagoon induces the flow to pass through the estuarine channels, reducing the RT in this area if compared to the Dry scenario. In the northwest region, for both scenarios, RT is 90 days. This means that the particles that were initially in that region remain in the lagoon domain. However, from RT results, one cannot know to where those particles were transported. Even though, if particles are retained in this natural embayment, the result would not be a completely realistic situation in eddy areas in natural flows, where diffusive processes would cause mixing with water parcels outside of the eddy area. Since a particle represents the centroid of a water mass distribution, it is important to remember that lagrangian modelling of RT considers advective and dispersive processes of particles but does not compute turbulent diffusion of water masses among particles. Therefore, in heterogeneous water bodies such as the Patos Lagoon, particles transported just by advective and dispersive processes could result in nonrealistic mixing situations, due to the lack of proper turbulent diffusion. 3.2. Times of Renewal Rates To present the results of the Times of Renewal Rates models, Figure 6 shows isolines maps of renewal rate at a specific TRR%. For this study and the idealized cases, the time of TR50% at the downstream station A, v. Figure 2 was chosen. A TR50% at Station A is the time when 50% of the water at A entered the modelling domain after the initial simulation time. Consequently, the other 50% is from waters that were already in the channel at the initial time, but certainly not in the same place as Station A. For the idealized cases, Figure 6 shows that the isolines of Renewal Rate, for the time of TR50% at Station A, for Test 1 and Test 2 are very similar, but the effects of the lateral inflow in Test 2 are noticeable. For Test 1, water renewal is homogeneous along the channel section at Station A. For Test 2, due to the lateral inflow, the Renewal Rate along the section of Station Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 On characteristic hydraulic times through hydrodynamic modelling … 13 A varies from 45% in the right margin of the channel to 80% in the left margin. For Test 3, the isolines show that a plume of water with lower Renewal Rates exits the lateral embayment and arrives at the end of the channel producing a variation of Renewal Rate from 10% to 60% across the channel section of Station A. Figure 6. Above: Map of isolines at the time TR50% at the center of the outflow section of the channel, Station A, for Test1 (TR50%= 11.1h), Test 2 (TR50%= 9.8h), and Test3 (TR50% = 11.4h). Below: Map of isolines at the time TR50% at the center of the lagoon, Station B, for the Dry scenario (TR50% = 41 days), and the Wet scenario (TR50% = 39 days). For the Patos Lagoon case, Figure 7 represents the isolines maps of renewal rate at the specific TR50% in station B located in the middle of the lagoon, as depicted in Figure 2. The higher discharge of Jacuí River in the Wet scenario is responsible for almost 100% of water renewal of Guaíba Lake, the embayment that receives this affluent. Jacuí River is also responsible for the greater water renovation of the north half of the lagoon, 20% higher for the Wet scenario if compared with Dry scenario. Observing the results of the natural northeast embayment for both scenarios, the influence of higher Jacuí River discharges accelerates water renewal up to TR50% = 40 days approximately. From this result, one can conclude that water Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 14 Laura Aguilera et al. parcels that initially were in this embayment at the beginning of the simulation, were mixed with more renovated waters that come from Jacuí River. This information, which cannot be derived from the RT results, is important for management and monitoring decisions. The saline intrusion region does not present relevant seasonal changes. Water renewal in this area occurs due to tidal and storm surge effects and water 100% renovated discharges of the two main river tributaries of this region. Notice that the isoline of more than 90% renovated near São Gonçalo Channel is more far away from the mouth of the channel in the Dry scenario than in the Wet scenario. This is the case because the intense discharge of Jacuí River blocks the flow of São Gonçalo Channel during the Wet scenario. Figure 7. Above: Map of isolines of Water Age at the end of the 24h simulation for Test 1 to Test 3. Below: Map of isolines of Water Age at the end of the three- month simulation for the Dry and Wet scenarios in Patos Lagoon. 3.3. Water Age During the Water Age simulation, as hydrodynamic circulation progresses, parcels of newer waters are mixed with older ones. Advection, diffusion and decay processes continue varying WA in space and time, so the value of WA becomes varied and variable. Figure 7 presents the WA spatial results at the end of 24h of simulation for the idealized cases. For each case, these results represent the average age of the water mixture at each point. As the inflows enter on the channels with WA = 0, the water parcels next to them, with WA > 0, Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 On characteristic hydraulic times through hydrodynamic modelling … 15 are mixed and renewed rapidly, decreasing the resulting WA of the mixture. This is noticed at the left of Figure 7, at the beginning of the channel for the three tests and at the center for Test 2 case, where there is an additional lateral inflow. The influence of the lateral inflow is noticed in the results of Test 2, where there are newer waters at the right margin of the channel. This analysis, together with those previously presented for Test 2 in the RT and TRR% sections, shows the importance of properly considering inflows in characteristic hydraulic time analyses in natural water bodies where rivers have a significant influence. At the final time of the simulation, where equilibrium is reached, both embayment margins present approximately values of WA=20h. For the modelling cases addressed here, the equilibrium is static because the flux is steady. The WA simulation considers the diffusion processes, so the water mixing is better represented in the results than in the Residence Time analyses. The Patos Lagoon maps of Figure 7 present the WA spatial results at the end of the three- month simulation for each scenario. The results show clearly the influence of river inflows in the northern part, and the influence of tides in the southern part. This limit is clear in the 32- day isoline in the central part of the lagoon for WA results. For both scenarios, as observed in Test 2 for the idealized channel, as the river inflows reach the lagoon with WA = 0, they mixed with water parcels with WA > 0 and renewed rapidly the surrounding areas. The water renewal is, therefore, highly related to the river discharge. Seasonal changes of Jacuí River discharges modifies WA in the northwest of the Patos Lagoon from 45 days for Dry scenario, to 35 days for the Wet scenario. As pointed out in the previous results, in the northeast of the lagoon there is a natural embayment that hinders water renewal. Water parcels positioned in this area did not mixed easily with the surrounding water parcels. This information is evident observing the Wet scenario results, since WA is 50 days in the embayment area and 37 days outside it. In the southern half of the lagoon, water renewal is more influenced by tidal effects. Comparing the results of WA in this region, there are no relevant differences between the two seasonal scenarios. Therefore, one could say that the most important seasonal differences in Water Age are mainly ruled by the seasonal Jacuí River discharge variations. In natural flows, there is no static equilibrium as occurs in steady flows. The equilibrium is dynamic, and, after enough time of simulation, the water age fluctuates around a value depending on the fluctuations of the main hydrodynamic forcing effects, such as tides or river flows fluctuations, for example. After three months of simulation for both scenarios, only the south of the lagoon and the Jacuí River region reached the dynamic equilibrium. The north and the northeast of the lagoon did not reach it, meaning that these areas would achieve higher values that 55 days of WA at their dynamic equilibrium, which makes this area especially vulnerable to eutrophication effects. Consequently, this region of Patos Lagoon must be monitored as it is more vulnerable to trophic processes. 4. CONCLUSIONS The results presented in this paper showed that, even in idealized situations with simple domains and controlled flux alterations, non-intuitive results for CHT arise. Therefore, a clear understanding of the concepts regarding different CHT, and the methodologies adopted to compute each case are of paramount importance. When considering the same idealized test, even though the Residence Time, the Times to Renewal Rates and the Water Age analyses represented the same hydrodynamics conditions, the isolines results are visually quite different for each case. These different results conform to the definitions of each concept and the methodology used to compute them. However, if the result interpretation is addressed careless or without a good understanding of the concepts and methodologies behind the characteristic hydraulic times, it could lead to wrong conclusions due to mistaken interpretations. Identifying Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 16 Laura Aguilera et al. correctly the regions with lower WRR and higher WA and RT is important because they indicate likely stagnant areas potentially vulnerable to eutrophication effects. This explains the importance of presenting the idealized channel results and discussions included in this paper before presenting the CHT results for Patos Lagoon. A discussion about lagrangian and eulerian approaches to compute characteristic hydraulic times has also been addressed. The application of the CHT modelling in Patos Lagoon, a heterogeneous water body, the traditional concept of Residence Time, even using the lagrangian approach that allows RT varying in space and time, showed that it is not ideal. The methodology adopted here considered neutral particles, which do not represent diffusion processes that is important in stagnation areas. The eulerian approach at the applied CHT model proved to be a better option since diffusivity is considered. If the objective is to analyze the time it takes for a given point of the modelling domain to reach a certain water renewal, it is recommended to use the Times of Renewal Rates. However, if the objective is to analyze for how long, on average, the waters remain in the predefined domain over time, it is recommended to apply the Water Age concept presented here. The Water Age concept proved to be a versatile and multifunctional characteristic hydraulic time in the idealized tests and in Patos Lagoon. A good understanding of the concept and computation of WA allows, depending on the characteristics of the case, an estimation of the Travel Time, Residence Time or Time of 50% of Renewal Rate of Waters of a region. Monitoring campaign decisions such as the number of sampling sites or the sampling time should be made after Water Age analyses, to see stagnation areas where relevant biogeochemical processes could occur. After analyzing the WA results for Patos Lagoon, the north and northeast areas were highlighted as the areas where quality monitoring is more needed. These results are useful to make decisions that could save funds in monitoring campaigns. Therefore, the use of WA as the characteristic hydraulic time is recommended rather than the other concepts addressed here. However, it has been also presented that each CHT gives diverse information, related to its own CHT definition and computation methodology, about the processes involved in water renewal. Consequently, for a better understanding of renewal processes in natural water bodies, it would be recommended that more than one CHT be analyzed. Finally, this study contributed to clarify widely used CHT concepts that have been frequently used without a unified definition in the literature, leading to misleading interpretations. The results presented here for Residence Time, Times to Renewal Rates and Water Age for simple and intuitive hydrodynamics conditions helped to describe the meaning and the correct interpretation of the results associated with the idealized tests and Patos Lagoon. The results presented for the CHT analysis in Patos Lagoon exemplifies the useful information that can be extracted from CHT analysis and the advantages of using CHT as a prerequisite for the development of water quality monitoring campaigns in natural water bodies. Thus, this work intends to serve as a guide for future application and results interpretation of these concepts in environmental management and monitoring programs. For a more precise characterization of the RT, TRR and WA in Patos Lagoon, a revision and actualization of the environmental data used for the modelling must be done, in addition to a calibration and validation process using water level and/or current data measured at different points of the lagoon. 5. ACKNOWLEDGES This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001; and by the COPPETEC Foundation. Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 On characteristic hydraulic times through hydrodynamic modelling … 17 6. REFERENCES ALDAMA, A. A. Theory and applications of two- and three-scale filtering approaches for turbulent flow simulation. 1985. Ph.D. (Thesis) - Department of Civil Engineering, Massachusetts Institute of Technology, Cambridge, 1985. ANA. Website. 2015. Available at: https://www.ana.gov.br/. Access: Jan. 2020. BACHER, C.; FILGUEIRA, R.; GUYONDET, T. Probabilistic approach of water residence time and connectivity using Markov chains with application to tidal embayments. Journal of Marine Systems, v. 153, p. 25–41, 2016. https://doi.org/10.1016/j.jmarsys.2015.09.002 BEAM, R. M.; WARMING, R. F. An Implicit Factored Scheme for the Compressible Navier- Stokes Equations. AIAA Journal, v. 16, n. 4, p. 393–402, 1978. https://doi.org/10.2514/3.60901 BEDFORD, K.; DAKHOUL, Y. Applying LES Turbulence Modeling to Open Channel Flow. In:APPLYING RESEARCH TO HYDRAULIC PRACTICE, 17-20 Aug. 1982, Jackson, Mississippi. Proceedings[...] Jackson: ASCE, 1982. BENDATI, M. M.; SCHWARZBACH, M. S. R.; MAIZONAVE, C. R. M.; ALMEIDA, L. B.; BRINGHENTI, M. L. Avaliação Da Qualidade Da Água Do Lago Guaíba (Rio Grande Do Sul, Brasil) Como Suporte Para a Gestão Da Bacia Hidrográfica. In: CONGRESSO INTERAMERICANO DE ENGENHARIA SANITÁRIA E AMBIENTAL, 27., 2000, Porto Alegre. Anais[...] Porto Alegre: ABES, 2000. BOLIN, B.; RODHE, H. A note on the concepts of age distribution and transit time in natural reservoirs. Tellus, v. 25, n. 1, p. 58–62, 1973. https://doi.org/10.1111/j.2153- 3490.1973.tb01594.x BORDAS, M. P.; CASALAS, A. B.; SILVEIRA, GONÇALVEZ, M. Circulação e dispersão em sistemas costeiros e oceânicos. Caso da Lagoa dos Patos. Relatório Técnico. Porto Alegre: IPH/UFRGS, 1984. COPPETEC. Projeto 16861: Modelo matemático aprimorado de quantificação de assoreamento dos acessos aquaviários nos portos contemplados - Porto de Rio Grande - RS. Rio de Janeiro, 2015. CRANK, J.; NICOLSON, P. A practical method for numerical evaluation of solutions of partial differential equations of the heat-conduction type. Advances in Computational Mathematics, v. 6, n. 2, p. 207–226, 1947. https://doi.org/10.1017/S0305004100023197 CUCCO, A.; UMGIESSER, G. The Trapping Index: How to integrate the Eulerian and the Lagrangian approach for the computation of the transport time scales of semi-enclosed basins. Marine Pollution Bulletin, v. 98, n. 1–2, p. 210–220, 2015. https://doi.org/10.1016/j.marpolbul.2015.06.048 DELEERSNIJDER, E.; CAMPIN, J. M.; DELHEZ, E. J. M. The concept of age in marine modelling I. Theory and preliminary model results. Journal of Marine Systems, v. 28, n. 3–4, p. 229–267, 2001. https://doi.org/10.1016/S0924-7963(01)00026-4 DELHEZ, É. J. M.; DE BRYE, B.; DE BRAUWERE, A.; DELEERSNIJDER, É. Residence time vs influence time. Journal of Marine Systems, v. 132, p. 185–195, 2014. https://doi.org/10.1016/j.jmarsys.2013.12.005 Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 18 Laura Aguilera et al. DNIT. EIA-RIMA para obras de dragagem de aprofundamento do Canal de Acesso ao Porto de Rio Grande - Volume II - Caracterização do meio físico. Rio Grande do Sul, 2007. DU, J.; SHEN, J. Water residence time in Chesapeake Bay for 1980–2012. Journal of Marine Systems, v. 164, p. 101–111, 2016. FERNANDES, E. H. L. Modelling the Hydrodynamics of the Patos Lagoon, Brazil. PhD (Thesis) - Faculty of Science and Technology, University of Plymouth, Plymouth, 2001. FURG. Relatório das Sondagens Geológicas para o EIA/RIMA - Dragagem de aprofundamento dos canais de acesso e bacias de evolução do Porto Novo (RS) e Porto de São José do Norte. Rio Grande do Sul, 2008. GONZÁLEZ-GORBEÑA, E.; ROSMAN, P. C. C.; QASSIM, R. Y. Journal of Ocean Engineering and Marine Energy, v. 1, n. 4, p. 421–433, 2015. https://doi.org/10.1007/s40722-015-0031-5 GRIFOLL, M.; JORDÀ, G.; ESPINO, M. Surface water renewal and mixing mechanisms in a semi-enclosed microtidal domain. The Barcelona harbour case. Journal of Sea Research, v. 90, p. 54–63, 2014. https://doi.org/10.1016/j.seares.2014.02.007 HARTMANN, C.; HARKOT, P. F. C. Influência do Canal de São Gonçalo no aporte de sedimentos para o estuário da Laguna dos Patos - RS. Revista Brasileira de Geociâncias, v. 20, p. 329–332, 1990. HUGUET, J.-R.; BRENON, I.; COULOMBIER, T. Characterisation of the Water Renewal in a Macro-Tidal Marina Using Several Transport Timescales. Water, v. 11, n. 10, p. 2050, 2019. https://doi.org/10.3390/w11102050 KISTLER, R. COLLINS, W.; SAHA, S.; WHITE, G.; WOOLLEN, J.; KALNAY, E.; CHELLIAH, M.; EBISUZAKI, W.; KANAMITSU, M.; KOUSKY, V.; VAN DEN DOOL, H.; JENNE, R.; FIORINO, M. The NCEP–NCAR 50–Year Reanalysis: Monthly Means CD–ROM and Documentation. Bulletin of the American Meteorological Society, v. 82, n. 2, p. 247–267, 2002. KJERFVE, B. Comparative Oceanography of Coastal Lagoons. Marine Biology and Coastal Research, p. 63–81, 1986. https://doi.org/10.1016/B978-0-12-761890-6.50009-5 LEONARD, A. Energy cascade in large-eddy simulations of turbulent fluid flows. Advances in Geophysics, v. 18, part A, p. 237–248, 1975. https://doi.org/10.1016/S0065- 2687(08)60464-1 LI, X.; SHEN, Y. Numerical simulation of the impacts of water level variation on water age in Dahuofang Reservoir. Frontiers of Earth Science, v. 9, n. 2, p. 209–224, 2015. https://doi.org/10.1007/s11707-014-0460-9 LIU, R. et al. Numerical Study on the Influences of Hydrodynamic Factors on Water Age in the Liao River Estuary, China. Journal of Coastal Research, v. 80, p. 98–107, 2017. https://doi.org/10.2112/SI80-014.1 MARQUES, W. C. FERNANDES, I. O.; MONTEIRO, M. H.; MOLLER, O. O. Numerical modeling of the Patos Lagoon coastal plume, Brazil. Continental Shelf Research, v. 29, n. 3, p. 556–571, 2009. https://doi.org/10.1016/j.csr.2008.09.022 Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 On characteristic hydraulic times through hydrodynamic modelling … 19 MARTELO, A. F.; TROMBETTA, T.B.; LOPES, B.V.; MARQUES, W.C.; MÖLLER, O. O. Impacts of dredging on the hydro morphodynamics of the Patos Lagoon estuary, southern Brazil. Ocean Engineering, v. 188, p. 106325, 2019. https://doi.org/10.1016/j.oceaneng.2019.106325 MOLLER, O. O. Hydrodynamique de la Lagune dos Patos (30° S, Bresil). [S.l.]: L’Universite Bordeaux I, 1996. MONSEN, N. E.; CLOERN, J. E.; LUCAS, L. V.; MONISMITH, S. G. A comment on the use of flushing time, residence time, and age as transport time scales. Limnology and Oceanography, v. 47, n. 5, p. 1545–1553, 2002. PEIXOTO, R. DOS S.; ROSMAN, P. C. C.; VINZON, S. B. A morphodynamic model for cohesive sediments transport. RBRH, v. 22, 2017. https://doi.org/10.1590/2318- 0331.0217170066 QI, H.; LU, J.; CHEN, X. SAUVAGE, S.; SANCHES-PÉREZ, J. M. Water age prediction and its potential impacts on water quality using a hydrodynamic model for Poyang Lake, China. Environmental Science and Pollution Research, v. 23, n. 13, p. 13327–13341, 2016. RIO GRANDE DO SUL. Portos do Rio Grande do Sul. 2019. Available at: http://www.portosrs.com.br/site/index.php. Access: Jan. 2020. ROSMAN, P. C. C. Modeling Shallow Water Bodies Via Filtering Techniques. [S.l.]: MIT, 1987. ROSMAN, P. C. C. Characteristic Hydraulic Times of the Jirau Hydropower Reservoir on the Madeira River – Braziliam Amazon Region. In: SILVA, R. C. V.; TUCCI, C. E. M.; SCOTT, C. A. (Eds.). Water and Climate - Modeling in large basins. [S.l.] Brazilian Water Resources Association, 2018. p. 95–132. ROSMAN, P. C. C. Referência Técnica do SisBaHiA®. Rio de Janeiro: Fundação Coppetec; COPPE, 2019. ROVERSI, F.; ROSMAN, P. C. C.; HARARI, J. Water renewal analysis of the Santos Estuarine System using computational modeling. Revista Ambiente & Água, v. 11, n. 3, p. 566- 585, 2016. http://dx.doi.org/10.4136/ambi-agua.1770 SEELIGER, U.; ODEBRECHT, C.; CASTELLO, J. P. (Eds.). Subtropical Convergence Environments. The Coast and Sea in the Southwestern Atlantic. Rio Grande: Springer, 1997. SILVA, R. A. G.; GALLO, M. N.; ROSMAN, P. C. C.; NOGUEIRA, I. C. M. Tidal inlet short- term morphodynamics analysed through the tidal prism longshore sediment transport ratio criterion. Geomorphology, v. 351, 2019. https://doi.org/10.1016/j.geomorph.2019.106918 SMAGORINSKY, J. General Circulation Experiments with the Primitive Equations. I. The basic experiment. Monthly Weather Review, v. 91, 1963. https://doi.org/10.1175/1520- 0493(1963)091%3C0099:GCEWTP%3E2.3.CO;2 TOLDO JR., E. E.; DILLENBURG, S. R.; CORRÊA, I. C. S.; ALEMIDA, L. E. S. B.; WESCHENFELDER, J. Sedimentação na Lagoa dos Patos e os Impactos Ambientais. In: CONGRESSO DA ASSOCIAÇÃO BRASILEIRA DE ESTUDOS DO QUATERNÁRIO, 16., 2017, Bertioga. Anais[...] Guarapari: ABEQUA, 2005. Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 20 Laura Aguilera et al. VAZ, A. C.; MÖLLER JR., O. O.; DE ALMEIDA., T. L. Análise quantitativa da descarga dos rios afluentes da Lagoa dos Patos. Atlântica, v. 28, n. 1, p. 13–23, 2006. VIERO, D. P.; DEFINA, A. Water age, exposure time, and local flushing time in semi-enclosed, tidal basins with negligible freshwater inflow. Journal of Marine Systems, v. 156, p. 16–29, 2016. https://doi.org/10.1016/j.jmarsys.2015.11.006 YING, C.; LI, X. LIU, Y.; YAO, W.; LI, R. Numerical study of water residence time in the Yueqing Bay based on the eulerian approach Numerical study of water residence time in the Yueqing Bay based on the eulerian approach. IOP Conference Series: Earth and Environmental Science PAPER, v. 153, n. 8, 2018. ZIMMERMAN, J. T. F. Mixing and flushing of tidal embayments in the western Dutch Wadden Sea part I: Distribution of salinity and calculation of mixing time scales. Netherlands Journal of Sea Research, v. 10, n. 2, p. 149–191, 1976. https://doi.org/10.1016/0077- 7579(76)90013-2 Rev. Ambient. Água vol. 15 n. 2, e2456 - Taubaté 2020 Ambiente & Água - An Interdisciplinary Journal of Applied Science ISSN 1980-993X – doi:10.4136/1980-993X www.ambi-agua.net E-mail: [email protected] Presence of pesticides, mercury and trihalomethanes in the water supply systems of Ibagué, Colombia: threats to human health ARTICLES doi:10.4136/ambi-agua.2477 Received: 25 Sep. 2019; Accepted: 16 Feb. 2020 Blanca Lisseth Guzmán Barragán1* ; Manuel Alejandro Gonzalez Rivillas2 ; Manuel Salvador Cuero Villegas3 ; Jose David Olivar Medina2 1Facultad de Ciencias Agropecuarias. Universidad de Ciencias Aplicadas y Ambientales (U.D.C.A), Calle 222, N° 55-37, Postal Code: 111166, Bogotá, Cundinamarca, Colombia 2Ibagué Saludable. Alcaldía de Ibagué. Secretaría de Salud Municipal de Ibagué, Calle 9 N° 2-59, Ibagué, Tolima, Colombia. E-mail: [email protected], [email protected] 3Ciencias Biologicas. Universidad del Tolima (UT), Calle 42, S/N, Postal Code: 730006299, Ibagué, Tolima, Colombia. E-mail: [email protected] *Corresponding author. E-mail: [email protected] ABSTRACT Chemical contamination of the water supply system caused by anthropic activities can cause adverse health effects. This study determined the presence of toxic metals, organic substances, pesticides and trihalomethanes in the water supply systems of the urban area of Ibague City. The economic and sanitary activities located in the 25 surface streams of the 32 water supply systems of the municipality were characterized. A total of 25 water samples were taken from the surface streams, and 35 samples in the water network of each drinking water service provider for the identification of pesticides (carbamates, organochlorines, organophosphorus), mercury, arsenic, cyanide, lead, cadmium, antimony, cobalt, selenium, silver, nickel and hydrocarbons. The presence of trihalomethanes was sampled after the treatment process given. A total of 775 economic and sanitary activities were detected in the surface streams of the water supply systems, highlighting the human settlements, agricultural and tourist activities impact on the water sources. Organochlorine pesticides (0.009-0.109 mg/L), mercury (0.001-0.004 mg/L) were identified in the water supply system in concentrations higher than those permitted by local regulation. Concentrations of trihalomethanes (0.064-1.260 mg/L) were detected in 68.7% of the water supply systems with treatment. The presence of chemical contaminants occurs mainly in communities with water supply systems of low complexity with high anthropic affectation. It is necessary to strengthen the assessment of hazards and risk by health surveillance, as well as intersectoral intervention for the protection of water sources and the improvement of water treatment technologies. Keywords: environmental health, mercury, pesticides, trihalomethanes, water contamination. Presença de pesticidas, mercúrio e trialometanos na água para consumo humano em Ibagué, Colômbia: ameaças à saúde humana RESUMO A contaminação química do abastecimento da água causada por atividades antrópicas pode causar efeitos adversos à saúde. O presente estudo propõe determinar a presença de metais This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 Blanca Lisseth Guzmán Barragán et al. tóxicos, substâncias orgânicas, pesticidas e trihalometanos dos sistemas de abastecimento da cidade de Ibague, Colômbia. Foram caracterizadas as atividades econômicas e sanitárias presentes em 25 fontes de água superficial de 32 sistemas de abastecimento de água da área urbana do município. Se coletaram 25 amostras de água das fontes superficiais de água e 35 amostras do sistema de abastecimento de água para identificação de pesticidas (carbamatos, organoclorados, organofosforados), mercúrio, arsênico, cianeto, chumbo, cádmio, antimônio, cobalto, selênio. prata, níquel e hidrocarbonetos. A presença de trihalometanos foi avaliada no pós-tratamento. No total, 775 atividades econômicas e sanitárias foram detectadas nas fontes de água superficial do sistema de abastecimento de água, destacando o impacto dos assentamentos humanos, das atividades agrícolas e turísticas nas fontes de água. Pesticidas organoclorados (0,009-0,109 mg / L), mercúrio (0,001-0,004 mg / L) foram identificados no sistema de abastecimento de água em concentrações superiores às permitidas pelos regulamentos. Concentrações de trihalometanos (0,064-1,260 mg / L) foram detectadas em 68,7% do sistema de abastecimento de água com tratamento. A presença de contaminantes químicos ocorre principalmente no abastecimento de água comunitaria de baixa complexidade com alta afetação antrópica. É necessário fortalecer a avaliação de perigos e riscos pela vigilância sanitária, bem como a intervenção intersetorial para a proteção de fontes de água e o aprimoramento das tecnologias de tratamento de água. Palavras-chave: contaminação da água, mercúrio, pesticidas, saúde ambiental, trihalometanos. 1. INTRODUCTION Water quality is an essential component of public health. Chemical contamination of water sources is increasing; 30% of sweet water is used by industry and municipalities, generating large areas of highly contaminated wastewater. Anthropogenic activities, such as industry, agriculture, and discharge of large amounts of organic and inorganic toxic fuels, increase the health risks associated with these substances (Schwarzenbach et al., 2010, Fawell and Nieuwenhuijsen, 2003). Industrial pollutants intensify the contamination of water systems because treatments that control infectious agents are not effective in removing many toxic chemicals from drinking water (Landrigan, 2018). In Colombia, the quality of water supply is regulated by Decree No. 1575/2007 and Resolution No. 2115/2007 (Colombia, 2007). In routine surveillance, some chemical substances are monitored, among them: zinc, calcium, phosphates, manganese, molybdenum, sulfates, chlorides, iron, aluminum, calcium, fluorides, nitrites, nitrates and magnesium. However, toxic chemicals, such as pesticides, mercury, arsenic, cyanide, lead, cadmium, antimony, cobalt, selenium and silver, are not routinely monitored by Colombian sanitary surveillance. In these cases, the toxic chemical substances are subject to surveillance if anthropic activities associated with the release of these substances are identified in water sources of the water supply system and their presence confirmed in the water supply according to Resolution No. 4716/ 2010 (Colombia, 2010). The increase in local agriculture, industry, mining, and increasing urbanization in Colombia implies an increase in potentially toxic substances in the water. An evaluation of the progress towards the goals for drinking water access of the Millennium Development Goals (MDGs) for Colombia shows a level of partial compliance with the established goals. By 1990, 88% of the total population had safe water sources, distributed in 97% of the urban population and 69% of the population in the rural areas, for which a goal of 99.2% and 78.1% respectively was established. By 2014, 91% of the population had access to safe water sources, 97% in urban areas and rising to 74% in rural areas, evidencing enormous inequities in the provision of the public service of safe water between these sectors, as well as critical territorial gaps that deserve Rev. Ambient. Água vol. 15 n. 2, e2477 - Taubaté 2020 Presence of pesticides, mercury and trihalomethanes in … 3 priority attention (UN, 2015). It is essential to understand that safe sources of water are defined as connections to the water supply, pipe, well, pump, bottled water, tank car, and public battery. In this definition, there is no emphasis on the evaluation of potability standards. Therefore, many safe water sources must be monitored for quality to determine their true impact on health. The monitoring of water quality carried out in 1,067 municipalities (96.8%) of Colombia in 2014 pointed out the problems of water quality, considering that only 195 (18.3%) met the standards established by the Colombian regulations presenting an acceptable IRCA (Water Quality Risk Index) of 502 (47%) within the partial compliance range, and 370 (34.7%) did not comply with the established standards (Guzman et al., 2015). The present study evaluated the presence of toxic metals, organic substances, pesticides and trihalomethanes in the water supply system of the urban area of the municipality of Ibagué, Colombia, considering the sanitary surveillance guidelines established in Resolution No. 4716/ 2010 in order to discuss its contributions and challenges. 2. METHODOLOGY 2.1. Study area The study was conducted in the city of Ibague located in the center-west of Colombia, on the central mountain range coordinates 4°26'16" N, 75°12'02" W at an altitude of 1,285 meters above sea level, with average annual total rainfall of 1,691 mm, and temperatures between 20º and 28ºC (IDEAM, 2017). The city has a territorial extension of 1,439 km², administratively divided in 13 communes in the urban area and 17 rural settlements, with a total of 558,805 inhabitants according to projections of the National Administrative Department of Statistics - DANE 2018 (Colombia, 2011). It has a total of 32 water supply systems in the urban area. The municipal water supply and sewerage service company serves 80% of the population, and 31 low complexity community-type water supplies, which serve 20% of the population in those sites of difficult access; only 16 water supplies have treatment plants built and operating. The water supply consists of 25 surface water sources that belong to the basins of Rio Totare, Rio Coello and Rio Opia. 2.2. Characterization of economic and sanitary activities in water sources The activities that affect the quality of the surface water source of the water supply system were identified, for which a survey was carried out with the environmental authorities and the water supply service companies. Subsequently, a characterization of the economic and sanitary activities present upstream of the intake was carried out through field visits by inspectors. To this purpose, a technical sheet was prepared which allowed the gathering of the economic and sanitary information of the water source: type of activities, coordinates, possibly associated chemical inputs, and occasional discharges. The characterization of the activities was carried out between September and December of 2017. During this period three trips were made through the water basin: one through the main channel of the basin and two through routes by the water dividing lines that delimit each basin (left and right limits of the basin), trying to cover the greatest of area. Subsequently, technical sheets were completed, and the activities were geo- referenced using Trimble GPS equipment SPS780 with a TSC2.SC.900 antenna. The information collected was systematized, and the coordinates were graphically mapped within the geodetic network of the Instituto Geográfico Agustín Codazzi-GAC using ArcGis software with its Arsmap 10.5 application. 2.3. Sampling A total of 60 water samples were taken: 25 samples, one in each surface water source of the pump intake, and 35 starting points of the distribution networks of the water supply system. Rev. Ambient. Água vol. 15 n. 2, e2477 - Taubaté 2020 4 Blanca Lisseth Guzmán Barragán et al. Four samples of the municipal water supply were taken due to the population served, and one sample for the communal water supply. The sampling was carried out in December 2017, following the guidelines for taking and presenting samples (APHA et al., 2005; Instituto Nacional de Salud, 2011), considering the specifications of each characteristic (see Table 1). The temperature and pH were measured in the samples taken. The reading of the free residual chlorine was included in the treated samples. The samples were then stored in refrigerators to keep them at temperatures from 2°C to 4°C, to be transported to the reference laboratory in Bogotá DC, considering the chain of custody, biosecurity measures and preservation conditions for transportation in order to guarantee the integrity of the sample. Table 1. Preservation of the samples. COMPOUND PRESERVATION Arsenic, cadmium, mercury, nickel, HNO3 was added until pH <2 was obtained and cooled to silver, lead, selenium, antimony, cobalt, ≤ 6°C carbamate Hydrocarbons Addition of HCl or H2SO4 until pH ≤ 2, Refrigerate at ≤ 6°C Free cyanide NaOH until pH ≤ 12. Refrigerate at ≤ 6°C Organochlorine pesticides Refrigerate at 4°C to 6°C. If additional chlorine is present (sodium thiosulfate 0,92 mL at 10%), adjust pH from 5 to 8 with either NaOH or H2SO4 Organophosphorus pesticides Refrigerate at 4°C to 6°C. Adjust pH from 5 to 8 with either NaOH or H2SO4 Trihalomethanes Cool to ≤ 2°C 2.4. Laboratory analysis The samples were processed in the Laboratory of Analysis of Water and Soils of Colombia ANASCOL S.A.S., a laboratory accredited by the Institute of Hydrology, Meteorology and Environmental Studies - IDEAM and the Interlaboratory Program of Quality Control of Drinking Waters -PICCAP. The parameters were analyzed in both raw and treated water; trihalomethanes were only analyzed in treated water (see Table 2). The methodologies for analyzing the selected characteristics were carried out according to the guidelines of the "Standard Methods for the Examination of Water and Wastewater," Edition 21 (21). The samples were processed in December 2017 and January 2018. The minimum values detectable by the techniques used are presented in Table 2; the results obtained were evaluated considering the minimum values acceptable by the resolution N° 2115/2007 of Colombia. The analysis of the presence of contaminants was carried out for the treated water supply systems and is not treated separately, considering the samples in the surface water source and in the supply network. Rev. Ambient. Água vol. 15 n. 2, e2477 - Taubaté 2020 Presence of pesticides, mercury and trihalomethanes in … 5 Table 2. Analytical characteristics and methodology for the analysis of the chemical water quality of the urban water supply of Ibagué, Colombia, 2017. MDV MVA VARIABLE METHOD * ** (mg/L) (mg/L) TOXIC METAL Atomic Absorption Spectrophotometry - Manual hydride Arsenic 0.01 0.01 generation. SM3114B Digestion Nitric Acid-SM 3030 E-Atomic Absorption Cadmium 0.001 0.003 Spectrophotometry direct flame Air-Acetylene. SM 3111B Mercury Atomic Absorption Spectrophotometry - Cold Vapor. SM3112B 0.001 0.001 Digestion Nitric Acid-SM 3030 E-Atomic Absorption Nickel 0.005 0.02 Spectrophotometry direct flame Air-Acetylene. SM 3111B Nitric Acid Digestion-SM 3030 E- Atomic Absorption Silver 0.02 NR Spectrophotometry direct flame Air-Acetylene. SM 3111B Nitric Acid Digestion-SM 3030 E- Atomic Absorption Lead 0.005 0.01 Spectrophotometry direct flame Air-Acetylene. SM 3111B Atomic Absorption Spectrophotometry - Manual hydride Selenium 0.0005 0.01 generation. SM3114B Digestion Nitric Acid-SM 3030 E-Atomic Absorption Antimony 0.3 0.02 Spectrophotometry direct flame Air-Acetylene. SM 3111B SM 3030 E SM 3113 B Digestion - AA - Graphite Oven Cobalt 0.001 NR (Electrothermal) ORGANIC SUBSTANCES Dissociable cyanide Distillation - Volumetric. SM 4500CN - A. B. C. D. I 0.4 0.05 Partition - Infrared / Determination Hydrocarbons. NTC 3362: Hydrocarbons 1 0.01 2011-11-30 Numeral 4. Method C / Numeral 7. Modified Method F. PESTICIDES China National Standard Method GB / T 5009.104-2003 Liquid- Carbamates 0.01 0.0001 liquid extraction, CG / NPD Liquid-Liquid Extraction. EPA 3510 C. Revision 3. December Organochlorine 1996- Gas Chromatography with Electron Capture Detector (GC 0.005 0.0001 pesticides / ECD). EPA 8081B. Revision 2. February 2007 Liquid Liquid Extraction US-EPA 3510C Revision 3. December Organophosphorus 1996-Gas chromatography with Nitrogen-Phosphorus detector 0.0025 0.0001 pesticides (GC / NPD). US-EPA 8141B Revision 2. February 2007. DISINFECTION SUB-PRODUCTS SM 6232B Gas chromatography with electron capture detector Trihalomethanes 0.004 0.2 (GC / EDC). US-EPA 8081 B. Revision 2. February 2007. *MDV: Minimum Detectable Value **MVA: Acceptable Maximum Value according to Resolution N° 2115/2007 of Colombia. 3. RESULTS AND DISCUSSION The laboratory results identified the presence of cadmium, mercury, and nickel in water sources and the supply network of some water supply at the established detectable concentrations. No arsenic, barium, molybdenum, silver, lead, selenium, molybdenum, cobalt, hexavalent chromium, surfactants, dissociable cyanide, hydrocarbons, carbamates and Rev. Ambient. Água vol. 15 n. 2, e2477 - Taubaté 2020 6 Blanca Lisseth Guzmán Barragán et al. organophosphorus pesticides were detected. The reference values for cadmium, nickel and antimony were below the VMA levels established by Colombia (see Table 3). Table 3. Results of the chemical analyses in water sources and supply network of the water supply system of the urban area of Ibagué, 2017. Water supply system Water supply Results MVA with presence of the system above Characteristic UNI1 (Min - Max) COL2 Characteristic MVA COL WS3 SN4 WS SN WS SN Cadmium mg/L 0.003 0.0015 0.0016 0.001-0.001 3 10 0 0 Mercury mg/L 0.001 0.001-0.003 0.001-0.004 9 11 9 11 Nickel mg/L 0.02 0.005 - 0.007 0.005-0.007 11 11 0 0 Antimony mg/L 0.02 0.005 0.03 1 0 0 0 Total mg/L 0.001 0.018 - 0.056 0.009-0.109 22 13 22 13 Organochlorines Alpha-BHC mg/L 0.0001 0.01 0.025-0.101 1 4 1 4 Heptachlor mg/L 0.0001 ND5 0.022 0 1 0 1 Aldrin mg/L 0.0001 0.014 - 0.040 0.075-0.064 16 9 16 9 Heptachlor epoxide mg/L 0.0001 ND 0.007-0.012 0 2 0 2 Endosulfan sulfate mg/L 0.0001 0.005 - 0.020 0.005-0.008 15 2 15 2 Total mg/L 0.2 NA6 0.064-1.260 NA 15 NA 11 Trihalomethanes Chloroform mg/L 0.2 NA 0.003-0.068 NA 14 NA 0 Bromodichloro mg/L 0.2 NA 0,003-0,028 NA 10 NA 0 Methane Dibromochlor mg/L 0.2 NA 0,058-0.074 NA 15 NA 10 Methane 1 UNI: Units 2 MVA COL: Acceptable Maximum Value Colombia, 3 WS: Water source, 4Supply network:, 5 NR: No Report, 6 NA: Does not apply. The analysis showed the presence of mercury mainly in community-type water supplies. Mercury is found in the environment in its inorganic and organic forms. Its inorganic form is present in surface and underground waters; mercury is transformed to methylmercury that enters the human body through ingestion (Díaz-Arriaga, 2014). It mainly affects the nervous and immune system, the digestive system, skin and lungs, kidneys and eyes. Children are vulnerable to mercury poisoning, which can lead to deterioration of the developing central nervous system, as well as lung and nephrotic damage (Bose-O'Reilly et al., 2010; Counter and Buchanan, 2004). The presence of mercury is a critical problem in public and environmental health in Colombia, due to the high exploitation of gold. More than 17 departments and 80 municipalities in the country are affected by gold mining (Díaz-Arriaga, 2014). Mercury has been identified in water sources in several regions of the country, such as the Ciénaga de Ayapel and the waters of the Cai River in the department of Chocó, as well as in the Ciénaga de Grande Achi in the department of Bolivar (Díaz-Arriaga, 2014; Marrugo-Negrete, 2015). Likewise, in the region of La Mojana, the presence of mercury in biological samples of mining workers was evidenced, establishing a statistical correlation with water sources as a source of contamination (Díaz et al., 2018). The analysis of pesticides evidenced the presence of organochlorines in the water source of 22 water supplies (68.7%) and the supply network of 13 water supplies (40.6%). The organochlorines identified were Alpha-BHC, heptachlor, aldrin, heptachlor epoxide and endosulfan sulfate, but carbamates and organophosphates were not identified. The values detected in both water sources and in the supply network were above the reference VMA. Organophosphates, organochlorines, carbamates and pyrethroids are among the most Rev. Ambient. Água vol. 15 n. 2, e2477 - Taubaté 2020 Presence of pesticides, mercury and trihalomethanes in … 7 commonly used pesticides. Organochlorine compounds can resist biodegradation, accumulate in the environment and become persistent organic pollutants that have been detected in animal and human tissues. It can have adverse effects on the endocrine system affecting the production of hormones, such as thyroid and sex hormones; in the nervous system it can cause neuronal effects and dysfunction of neurotransmitters and affect liver function besides being potentially mutagenic and carcinogenic (Hendry-Hofer et al., 2019; Nicolopoulou-Stamati, et al., 2016; Zaragoza-Bastida et al., 2016). Pesticides have been widely identified in water sources in Colombia. At the Ciénaga de Grande de Lorica in the department of Córdoba, α-BCH, β-BCH and γ-BCH, aldrin and heptachlor epoxide organochlorines were identified which exceeded the individual concentration of pesticides allowed by the national regulations (Lans et al.,2008). An analysis of exposure to pesticides of the inhabitants of the riverside of the Bogotá River evidenced the presence of organochlorine and organophosphorus pesticides in the river water and fish, and ethylenethiourea in human biological samples (0: in biological samples of human origin) (Monsalve et al., 2012). With respect to water supply consumption, a study was carried out in Soacha (department of Cundinamarca) which analyzed the presence of mercury and organophosphorus and carbamate pesticide residues, identifying values below the Acceptable Maximum Values (VMA) (Silva et al., 2015). In Cali, an analysis of mercury, diuron and 2,4 diclofenac acetic acid in the city's water supply concluded that these substances were absent (Echeverry et al.,2015). The water supply systems mentioned are highly complex; the water supplies analyzed in the present study presented highly dangerous pollutants, mainly in the community water supply system, evidencing the problems of this type of system. To fulfill the goals of the SDGs (Sustainable Development Goals), it is necessary to define public policies and investments that strengthen the community treatment systems of the water supply with sustainable alternative solutions that recognize their technical-administrative nature for reaching the goals of water safety for the country. The presence of trihalomethanes was identified in the water supply of 15 of the 16 water supplies with treatment. Chloroform, bromodichloromethane and dibromochloromethane were analyzed in 11 water supplies (68.7%) with detected values above the VMA. Trihalomethanes are byproducts derived from the oxidation of organic matter in chlorination; they have been associated with alterations of the liver, kidney, nervous and reproductive system, showing carcinogenic and mutagenic effects (Kim et al., 2017; Sanchez, 2008). Through the analysis of trihalomethanes, values higher than those established in the regulations were identified in 68.7% of the water supplies with treatment, including conventional and communal-type water supply. In the municipality of Pereira, the presence of trihalomethanes in 75 water samples was evaluated in the water supply of the company Aguas y Aguas de Pereira, concluding that all samples showed results within the VMA established by the regulations (Vargas et al., 2015). The rate and the degree of formation of the trihalomethanes may increase depending on the concentration of chlorine and humic acids, the temperature, the pH and the concentration of bromide ion (WHO, 2017). The World Health Organization (WHO) recommends implementing basic strategies to reduce the concentration of trihalomethanes, such as: (a) changing process conditions (including the elimination of precursor compounds prior to the application of the disinfectant); (b) changing the disinfectant to one less prone to produce by-products in the water source; (c) use non-chemical disinfection methods; (d) eliminate them before water distribution (WHO, 2017). In the field visits by inspectors, 29 wastewater sources were identified that flow directly into 13 water sources of 19 water supplies, 96.5% of which were derived from human settlements and 3.5% from agricultural activities. In the characterization of the economic and sanitary activities upstream of the intake, a total of 775 activities were identified on the margin Rev. Ambient. Água vol. 15 n. 2, e2477 - Taubaté 2020 8 Blanca Lisseth Guzmán Barragán et al. of the streams of the water supply. The source with the highest number of activities was the River Combeima with 19.4% (source of a water supply), followed by La Volcana Stream with 9.82% (source of one water supply ), El Tejar Stream with 8.07% (source of one water supply) and La Granate Stream with 5.14% (source of three water supply ). The economic and sanitary activities identified are due to human settlements (53.1%), agricultural activities (42.5%), sand and clay extraction (1.9%), tourism (1.7%) and construction (0, 8%). The most significant activity was human settlements associated with the increase in population and urbanization in the peripheries, where the sources of the water supply are located. A highly diversified agricultural and livestock exploitation was observed: coffee, plantain, cocoa, kidney bean, banana, lulo (Quito orange), blackberry, corn, beans, avocado, vegetables, cassava and orange, poultry, pig, livestock, pisciculture and horse stalls, many of which are on the margin of the ravine without any delimitation. Likewise, the study identified 63 forested areas and 17 disaster zones. There was no direct relationship between the number of economic and sanitary activities present at the water source with the presence of contaminants in the drinking water. In systems with conventional treatments, the contaminants were not identified, while in community systems that were supplied by surface sources with high percentage supply systems with contaminants and others without water contaminants were identified. It is crucial to prioritize the protection of water sources, especially in those cases not having efficient treatment. The WHO, through the Water Safety Plan, recommends monitoring the sources continuously by service providers. Knowing the nature of the quality of the raw water, the dynamics of the water sources, the changes related to weather phenomena or other circumstances, including runoff or recharge processes, as well as verifying and correcting land use in the catchment basin, is required in order to carry out risk management at the water sources of the water supply. In the monitoring of the water quality in terms of the chemical pollutants studied, there are significant limitations that must be overcome in order to be able to evaluate more rigorously the risks to health derived from those chemicals that are considered in the regulations. These include the analysis of health effects associated with such chemicals, considering the frequency of exposure and the concentrations at which the population will be exposed. The likelihood of health effects depends on toxicity and concentration, but also depends on the period of exposure, since for most chemicals, health impacts are associated with long-term exposure (UN, 1999). The regulations establish that the definition of the characteristics that must be analyzed in the water source and the water supply is determined from the field visits by inspectors; 29 wastewater sources were identified that flow directly into 13 water sources of 19 water supplies of the economic and sanitary activities upstream of the intake. It is essential to mention that there are difficulties in performing exhaustive field visits by inspectors, considering the geographical adversity and the runoff potential of the leachate, adding a significant margin of error. Subsequently, the sampling established for the identification of these pollutants in the water source and the distribution network is annual or semi-annual, depending on the population served, sampling that is not quite representative, knowing the dynamics of the basins of the water sources. The definition of the characteristics monitored in the supply network is taken from the sampling, and the results of the first sample carried out in the water source which, as mentioned, is poorly representative, being that the definition of contaminants in the network will be subjective. In this study, we detected contaminants present in the water supply and not in the water source, as well as mining contaminants without their prior identification in the field visits by inspectors. Another important aspect is the analytical availability in the territories; it is crucial to consider that the analysis of these parameters is recent in the regulations and the methodologies present high costs. Many of the territories do not have an adequate laboratory setup for testing Rev. Ambient. Água vol. 15 n. 2, e2477 - Taubaté 2020 Presence of pesticides, mercury and trihalomethanes in … 9 these substances and few laboratories in the national public health network have implemented these methodologies. On the other hand, the methodologies available in some cases are not able to identify low concentrations of the substance analyzed. Therefore, laboratories require strengthening of their infrastructure and laboratory techniques, as well as their measurement and calibration capabilities. Finally, the VMA for pesticides in the Colombian regulations are not specific for each of the chemical groups, which makes its analysis cumbersome. A general value is established for all pesticides, without considering that each one in the groups presents a particular mechanism of action and established lethal dose. It is essential, then, to develop regulations relating to the analysis of pesticides in water in Colombia. The regulations in the legal frameworks of Brazil, Chile, Uruguay and Venezuela follow the guidelines of WHO, where there are specifications for each chemical group of pesticides (Pinto et al., 2012). 4. CONCLUSIONS This study identified the presence of contaminants such as mercury, pesticides and trihalomethanes in water of urban supply systems, showing the weaknesses of the treatment system in eliminating these high risk chemical substances. It is observed that some supply systems with “safe sources” have chemical contamination, which makes it essential to determine the real risk to the populations served by these systems, considering the presence of water contaminants. The results show the lack of protection of the hydraulic sources of urban aqueducts, associated with the presence of economic and sanitary activities and discharges from settlements, agriculture, mining, tourism and construction that increase the pollution load of the sources. It is therefore necessary to strengthen the monitoring of water sources and to promote the timely management of hazards at the sources. It is also important to strengthen the analysis of chemical substances and the evaluation of hazards and risk by the health authorities. Water quality monitoring should opt for new, more representative and accurate tools to assess the quality of drinking water and its impacts on health. 5. ACKNOWLEDGEMENTS This study was funded by the Mayor's Office of Ibagué, in support of the development of research that strengthens Public Health Actions. 6. REFERENCES APHA; AWWA; WEF. Standard Methods for the Examination of Water and Wastewater. 21. ed. Washington, 2005. p. 541. BOSE-O'REILLY, S.; MCCARTY, K. M.; STECKLING, N.; LETTMEIER, B. Mercury exposure and children's health. Current Problems in Pediatric and Adolescent Health Care, v. 40, p. 186-215, 2010. 10.1016/j.cppeds.2010.07.002 COLOMBIA. Departamento Administrativo Nacional de Estadísticas. Estimación estadísticas vitales en los niveles de departamentos y municipio. Bogotá, 2011. COLOMBIA. Ministerio de la Protección Social. Ministerio de Ambiente, Vivienda y Desarrollo Territorial. Resolución 2115 de 22 junio de 2007, por medio de la cual se señalan características, instrumentos básicos y frecuencias del sistema de control y vigilancia para la calidad del agua para consumo humano. Diario Oficial, Bogotá, n. 46679, 4 julio 2007. Rev. Ambient. Água vol. 15 n. 2, e2477 - Taubaté 2020 10 Blanca Lisseth Guzmán Barragán et al. COLOMBIA. Ministerio de la Protección Social. Ministerio de Ambiente, Vivienda y Desarrollo Territorial. Resolución 4716 de 21 diciembre de 2010, por medio de la cual se reglamenta el parágrafo del artículo 15 del Decreto 1575 de 2007. Diario Oficial, Bogotá, n. 47930, 21 diciembre 2010. COUNTER, S. A.; BUCHANAN, L. H. Mercury exposure in children: a review. Toxicology and Applied Pharmacology, v. 98, p. 209-230, 2004. 10.1016/j.taap.2003.11.032 DÍAZ-ARRIAGA, F.A. Mercurio en la minería del oro: impacto en las fuentes hídricas destinadas para consumo humano. Revista de Salud Pública, v. 16, p. 947-957, 2014. https://doi.org/10.15446/rsap.v16n6.45406 DÍAZ, S.; MUÑOZ-GUERRERO, M.; PALMA-PARRA, M.; BECERRA-ARIAS, C; FERNÁNDEZ-NIÑO, J. Exposure to Mercury in Workers and the Population Surrounding Gold Mining Areas in the Mojana Region, Colombia. International Journal of Environmental Research and Public Health, v. 15, p. 1-15, 2018. https://dx.doi.org/10.3390/ijerph15112337 ECHEVERRY, G.; ZAPATA, A.M.; PAÉZ, M.I.; MÉNDEZ, F.; PEÑA, M. Valoración del riesgo en salud en un grupo de población de Cali, Colombia, por exposición a plomo, cadmio, mercurio, ácido 2, 4-diclorofenoxiacético y diuron, asociada al consumo de agua potable y alimentos. Biomédica, v. 35, p. 110-19, 2015. https://doi.org/10.7705/biomedica.v35i0.2464 FAWELL, J.; NIEUWENHUIJSEN, M. J. Contaminants in drinking water Environmental pollution and health. British Medical Bulletin, v. 68, p. 199-208, 2003. https://doi.org/10.1093/bmb/ldg027 GUZMÁN, B. L.; NAVA, G.; BEVILACQUA, P. La calidad del agua para consumo humano y su asociación con la morbimortalidad en Colombia, 2008-2012. Biomédica, v. 35, p. 177-90, 2015. http://dx.doi.org/10.7705/biomedica.v35i0.2511 HENDRY-HOFER, T. B.; NG, P. C.; WITEOF, A. E.; MAHON, S. B.; BRENNER, M.; BOSS, G. R. et al. A Review on Ingested Cyanide: Risks, Clinical Presentation, Diagnostics, and Treatment Challenges. Journal of Medical Toxicology, v. 15, p. 128-133, 2019. https://dx.doi.org/10.1007/s13181-018-0688-y INSTITUTO DE HIDROLOGIA METEOROLOGIA Y ESTUDIOS AMBIENTALES. Características climatológicas de ciudades principales y municipios. Bogotá, 2017. p. 48. INSTITUTO NACIONAL DE SALUD. Manual de instrucciones para la toma, preservación y transporte de muestras de agua de consumo humano para análisis de laboratorio. Bogotá, 2011. p. 95. KIM, K. H.; KABIR, E.; JAHAN, S. A. Exposure to pesticides and the associated human health effects. Science of the Total Environment, v. 575, p. 525-535, 2017. https://dx.doi.org/10.1016/j.scitotenv.2016.09.009 LANDRIGAN, P. J.; FULLER, R.; ACOSTA, N. J.; ADEYI, O.; ARNOLD, R.; BALDÉ, A. B.; et al. The Lancet Commission on pollution and health. The Lancet, v. 391, p. 462- 512, 2018. LANS, E.; NEGRETE, J. L. M.; DÍAZ, B. Estudio de la contaminación por pesticidas organoclorados en aguas de la Ciénaga Grande del Valle Bajo del río Sinú. Temas Agrarios, v. 13, p. 49-56, 2008. https://doi.org/10.21897/rta.v13i1.664 Rev. Ambient. Água vol. 15 n. 2, e2477 - Taubaté 2020 Presence of pesticides, mercury and trihalomethanes in … 11 MARRUGO-NEGRETE, J.; PINEDO-HERNÁNDEZ, J.; DÍEZ, S. Geochemistry of mercury in tropical swamps impacted by gold mining. Chemosphere, v. 134, p. 44-51, 2015. https://dx.doi.org/10.1016/j.chemosphere.2015.03.012 MONSALVE, A. S.; CRIOLLO, S. M. D.; URIBE, M. E. V.; MANTILLA, J. F. G.; FORERO, A.R. Exposición a plaguicidas en los habitantes de la ribera del río Bogotá (Suesca) y en el pez Capitán. Revista Ciencia de la Salud, v. 10, p. 29-41, 2012. NICOLOPOULOU-STAMATI, P.; MAIPAS, S.; KOTAMPASI, C.; STAMATIS, P.; HENS, L. Chemical Pesticides and Human Health: The Urgent Need for a New Concept in Agricult. Frontiers in Public Health, v. 4 p. 148, 2016. 10.3389/fpubh.2016.00148 PINTO, V. G.; HELLER, L.; BASTOS, R. K. X. Drinking water standards in South American countries: convergences and divergences. Journal Water and Health, v. 10, p. 295-310, 2012. https://doi.org/10.2166/wh.2012.087 SÁNCHEZ, Z. A. Efectos de los trihalometanos sobre la salud. Higiene Sanidad Ambiental, v. 8, p. 280-290, 2008. SCHWARZENBACH, R. P.; EGLI, T.; HOFSTETTER, T. B.; VON GUTEN, U.; WEHRLI, B. Global water pollution and human health. Annual Review of Environment and Resources, v. 35, p. 109–36, 2010. https://doi.org/10.1146/annurev-environ-100809- 125342 SILVA, E.; VILLARREAL, M. E.; CÁRDENAS, O.; CRISTANCHO, C. A.; MURILLO, C.; SALGADO, M. A. et al. Inspección preliminar de algunas características de toxicidad en el agua potable domiciliaria, Bogotá y Soacha, 2012. Biomédica, v. 35; p. 152-66, 2015. http://dx.doi.org/10.7705/biomedica.v35i0.2538 VARGAS, O. I. V.; BELTRÁN, L.; FRANCO, P; NAVARRETE, C. H. M.; RODRÍGUEZ, E. J. A. et al. Determinación de trihalometanos en aguas de consumo humano por microextracción en fase sólida-cromatografía de gases en Pereira, Colombia. Revista Colombiana Química, v. 44, p. 23-29, 2015. https://doi.org/10.15446/rev.colomb.quim.v44n1.54041 UN. Programa de las Naciones Unidas para el Desarrollo: Objetivos de Desarrollo Sostenibles, Colombia; herramientas de aproximación al contexto local. Bogotá: PNUD, 2015. p. 342. UN. Programa de las Naciones Unidas para el Medio Ambiente: Evaluación de riesgos químicos. Ginebra: PNUMA/IPCS, 1999. p. 239. WHO. Guidelines for drinking-water quality. 4th ed. Ginebra, 2017. p. 63. ZARAGOZA-BASTIDA, A.; VALLADARES-CARRANZA, B.; ORTEGA-SANTANA, C.; ZAMORA-ESPINOSA, J.; VELÁZQUEZ-ORDOÑEZ, V.; APARICIO-BURGOS, J. Repercusiones del uso de los organoclorados sobre el ambiente y salud pública. Abanico Veterinario, v. 6, p. 43-55, 2016. Rev. Ambient. Água vol. 15 n. 2, e2477 - Taubaté 2020 Ambiente & Água - An Interdisciplinary Journal of Applied Science ISSN 1980-993X – doi:10.4136/1980-993X www.ambi-agua.net E-mail: [email protected] Retrieval and mapping of chlorophyll-a concentration from Sentinel-2 images in an urban river in the semiarid region of Brazil ARTICLES doi:10.4136/ambi-agua.2488 Received: 25 Oct. 2019; Accepted: 26 Jan. 2020 Alessandro Rhadamek Alves Pereira1* ; João Batista Lopes2 ; Giovana Mira de Espindola1 ; Carlos Ernando da Silva3 1Departamento de Transportes. Programa de Pós-Graduação em Desenvolvimento e Meio Ambiente. Universidade Federal do Piauí (UFPI), Campus Universitário Ministro Petrônio Portella, S/N, CEP: 64049-550, Teresina, PI, Brazil. E-mail: [email protected] 2Departamento de Zootecnia. Programa de Pós-Graduação em Desenvolvimento e Meio Ambiente. Universidade Federal do Piauí (UFPI), Campus Universitário Ministro Petrônio Portella, S/N, CEP: 64049-550, Teresina, PI, Brazil. E-mail: [email protected] 3Departamento de Recursos Hídricos, Geotecnia e Saneamento Ambiental. Programa de Pós-Graduação em Desenvolvimento e Meio Ambiente. Universidade Federal do Piauí (UFPI), Campus Universitário Ministro Petrônio Portella, S/N, CEP: 64049-550, Teresina, PI, Brazil. E-mail: [email protected] *Corresponding author. E-mail: [email protected] ABSTRACT Recently, the Poti river mouth region has experienced environmental impacts that resulted in a change of landscape in its dry season, highlighting the eutrophication and proliferation of phytoplankton, algae, cyanobacteria and aquatic plants. Considering the aspects related to water-quality monitoring in the semiarid region of Brazil from remote sensing, this study aimed to evaluate the performance of Sentinel-2A satellite data in the retrieval of chlorophyll-a concentration in Poti River in Teresina, Piaui, Brazil. The chlorophyll-a concentration retrieval and mapping methodology involved the study of the water surface reflectance in Sentinel-2A images and their correlation with the chlorophyll-a data collected in situ during the years 2016 and 2017. The results generated by the Chl-1, Ha et al. (2017), Chl-2, Page et al. (2018), and Chl-3, Kuhn et al. (2019) equations show the need for calibrating the algorithms used for the Poti River water components. However, the empirical algorithm Chl-2 shows a correlation has been established to identify the spatiotemporal variation of chlorophyll-a concentration along the Poti River broadly and not punctually. The spatial distribution of this pigment in maps derived from Sentinel-2A is consistent with the pattern of occurrence determined by the in situ data. Therefore, the MSI sensor proved to be a tool suitable for the retrieval and monitoring of chlorophyll-a concentration along the Poti River. Keywords: Poti river, remote sensing, water quality. Recuperação e mapeamento da concentração de clorofila-a a partir de imagens do Sentinel-2 em um rio urbano na região semiárida do Brasil RESUMO A região da foz do rio Poti experimentou nos últimos anos impactos ambientais que resultaram na mudança da sua paisagem na estação seca, destacando-se a eutrofização e a This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 Alessandro Rhadamek Alves Pereira et al. proliferação de fitoplâncton, algas, cianobactérias e plantas aquáticas. Considerando os aspectos relacionados ao monitoramento da qualidade da água na região semiárida do Brasil a partir do sensoriamento remoto, este estudo teve como objetivo avaliar o desempenho dos dados do satélite Sentinel-2A, na recuperação da concentração de clorofila-a no rio Poti em Teresina, Piauí, Brasil. A metodologia de recuperação e mapeamento da concentração de clorofila-a envolveu o estudo da reflectância da superfície da água nas imagens Sentinel-2A e a respectiva correlação com dados in situ de clorofila-a, coletados em pontos de monitoramento, durante os anos de 2016 e 2017. Os resultados gerados pelas equações Chl-1, Ha et al., (2017), Chl-2, Page et al., (2018), e Chl-3, Kuhn et al., (2019), mostram a necessidade de uma calibração dos modelos utilizados aos componentes das águas do rio Poti. No entanto, o algoritmo empírico Chl-2 mostra que uma correlação foi estabelecida para identificar a variação espaço-temporal das concentrações de clorofila-a ao longo do rio Poti de maneira ampla e não mais pontual. A distribuição espacial desse pigmento nos mapas oriundos do Sentinel-2A é consistente com o padrão de ocorrência determinado pelos dados in situ. Portanto, o sensor MSI provou ser uma ferramenta adequada para a recuperação e monitoramento da concentração de clorofila-a ao longo do rio Poti. Palavras-chave: qualidade da água, rio Poti, sensoriamento remoto. 1. INTRODUCTION Disorderly development in large urban centres, devoid of any planning and with increasing levels of environmental degradation, drastically affects water availability and especially its quality (Vargas et al., 2018). The quality of the river water is affected by factors such as the increase of domestic and industrial pollutants that favour the eutrophication of the river water. The eutrophication that can lead to the death of aquatic fauna and flora, turning the water unfit for consumption and other uses (Esteves, 2011; Jorge and Lobo, 2019). Water-quality monitoring is a challenging process as data collection is insufficient or non- existent for most bodies of water. Punctual samples do not always portray the dynamics of water constituents, because the river is a highly dynamic lotic ecosystem that requires the collection of a large number of quality parameters to understand spatiotemporal variations and monitor changes (Prasad et al., 2018; Kuhn et al., 2019; Martins, 2019). In contrast, some authors have adopted an efficient approach that integrates diverse in situ data with remote sensing images to monitor the factors that affect water quality and understand the limnological processes, because satellite imagery provide the synoptic, continuous and long-term observation (Ha et al., 2017; Pinardi et al., 2018; Martins, 2019). The European Space Agency (ESA) has launched the mission Sentinel-2 with two identical satellites. The MultiSpectral Instrument (MSI) onboard the satellites is a 13-band passive optical sensor in a 20.6° orbital field of instrumental view. These features, in addition to a 10 m spatial resolution and five-day high temporal resolution, make the MSI sensor a suitable instrument for the retrieval of biophysical parameters in inland waters compared to other satellite missions designed for such applications as Landsat-8 / OLI, Sentinel-3 / OLCI, Aqua / MODIS (ESA, 2019; Pinardi et al., 2018; Pereira-Sandoval et al., 2019). Studies on the use of Sentinel-2A images in the retrieval and mapping of chlorophyll-a focus on a limited number of band ratio empirical algorithms. These models are based on statistical relationships between in situ measurements of water constituents and radiometric data from the satellite sensor, which provide the best correlation between reflectance data and the concentration of optically active water constituents at different wavelengths (Ogashawara et al., 2017). The commonly used two band-ratio algorithms are based on the ratios of the blue (440 and 510 nm) and green regions (550 and 555 nm), of the red (670 and 675 nm) and near Rev. Ambient. Água vol. 15 n. 2, e2488 - Taubaté 2020 Retrieval and mapping of chlorophyll-a … 3 infrared (NIR) regions (685 and 710 nm), and of the green (550 and 555 nm) and red regions (670 and 675 nm) (Mouw et al., 2015; Toming et al., 2016; Ha et al., 2017). In the semiarid region of Brazil, in the city of Teresina, in the state of Piaui, the urban riverbed of the Poti River has experienced intense environmental impacts in recent years, leading to changes in its landscape in the dry season, highlighting eutrophication and the proliferation of phytoplankton, algae, cyanobacteria and mainly from aquatic plants (Costa, 2014; Santos, 2017). The Sanitation Laboratory at the Federal University of Piaui has estimated chlorophyll-a concentration in punctual samples of the Poti River from laboratory analyses in 2016 and 2017. However, this sampling is a costly and low-temporal frequency procedure. The application of remote sensing can monitor large extensions of the Poti River over a long period and with a high temporal frequency, reducing efforts and resources, because six Sentinel-2 images are acquired monthly in the study area. In this context, this study evaluated the performance of the Sentinel-2A satellite data in the retrieval of chlorophyll-a concentrations in Poti River in Teresina, Piaui, Brazil. This is the first attempt to use remote-sensing techniques to monitor the spatial and temporal variability of water quality parameters in order to support the decision-making process, regarding preventive and corrective environmental management of the intense environmental impacts that occur in the Poti River, mainly in the dry season. 2. MATERIALS AND METHODS 2.1. Study area The study area, as shown in Figure 1, corresponds to the 36.8 km urban stretch along the Poti River, located in the municipality of Teresina, which is the largest city and the capital city of the state of Piaui, Brazil. This section of the river was chosen due to the location of the water quality monitoring sample points that have been carried out by the Sanitation Laboratory at the Federal University of Piaui. Figure 1. Study area: A) location of the study area in the context of Brazil's biomes (Brasil, 2017); B) location of Teresina in the state of Piaui; and, C) In the image Sentinel-2A L2A, acquired in August 2019 (ESA, 2019), shows the urban stretch of the Poti River in Teresina, with the location of the seven chlorophyll-a concentration monitoring points. From point PT-05, the environmental impacts occurred in 2014 (Costa, 2014) and 2018, upstream and 2015, downstream are observed. Rev. Ambient. Água vol. 15 n. 2, e2488 - Taubaté 2020 4 Alessandro Rhadamek Alves Pereira et al. The Poti River originates in the state of Ceara, in the city of Algodoes, and empties into the River Parnaiba, in Teresina. River Poti’s mouth flows around 1.3 m³ s-1, on average in the driest quarter. The studied area has an approximate area of 3.7 km² and an average width of 100 m in the rainy season and, during the dry season, it can be reduced to a few meters wide and a few centimetres deep in some places (Mendes-Câmara, 2011). The region is in the transition zone between the Cerrado and Caatinga biomes, in which the predominant natural vegetation is mixed forests that are being replaced by areas of agriculture and degraded vegetation (Espindola et al., 2017). The climate of the region is characterized as tropical equatorial zone, warm, semiarid, with a dry season from July to November and a rainy season from January to April, an average annual temperature and precipitation of 27.4ºC and 1.325 mm, in that order (IBGE, 2015; INMET, 2018). In the last four decades, Teresina, with 1,391.046 km² of area, has suffered high rates of urban expansion (IBGE, 2017). The city urbanization tendencies show that urban expansion has been larger than the population growth, causing problems related to the occupation of flood regions in the confluence of the Parnaiba and Poti Rivers, the contamination of the rivers themselves, the increase of the traffic, the increase of air pollution, lack of adequate housing and general infrastructure in peripheral areas (Espindola et al., 2017). It is noteworthy that Teresina has only 61.6% of households with adequate sanitation (IBGE, 2017). 2.2. Remote sensing data acquisition and preprocessing In this study, the remote-sensing data has been obtained by the Sentinel-2A satellite, available on the Copernicus Open Access Hub web platform (ESA, 2019). The images have the size, spatial and radiometric resolution of 100 km x 100 km, 10 m, 20 m and 60 m, and 12 bits, respectively. The Level-1C (L1C) product downloaded is pre-processed, orthorectified, georeferenced to the Universal Transverse Mercator projection using the World Geodetic System 84 datum, and radiometrically calibrated for top-of-reflectance atmosphere (ESA, 2018). The atmospheric correction was processed in the downloaded images using the Sen2Cor- 2.5.5 processor, available in the Sentinel Application Platform (SNAP-6) program toolbox, resulting in Level-2A (L2A) product, radiometrically calibrated for bottom-of-atmosphere reflectance. As the algorithm used in the correction described above processes bands of different spatial resolutions, the images were resampled to 20 m by the tool (ESA, 2018). The specifications of Sentinel-2A bands used in this study are presented in Table 1 (ESA, 2018; SINERGISE, 2018). Table 1. Bands specifications for Sentinel-2A. Central Spatial Wavelength Band wavelength resolution Capabilities (nm) (nm) (m) Is useful for soil and vegetation B02 492.4 458-523 10 discrimination forest type mapping; Is Blue absorbed by chlorophyll Gives excellent contrast between clear and B03 559.8 543-578 10 turbid water, and fairly well penetrates clear Green water Reflects well from dead foliage and is useful B04 Red 664.6 650-680 10 for identifying vegetation types, soils and urban features B05 Red 704.1 698-713 20 For classifying the vegetation edge 1 Rev. Ambient. Água vol. 15 n. 2, e2488 - Taubaté 2020 Retrieval and mapping of chlorophyll-a … 5 The multispectral images have been selected considering the dates available from 2016, the Sentinel-2A satellite launch period until the end of 2017 according field data, following the criteria of cloud-free in study area, totalling a set of eight scenes, in the orbit 138, with the subsequent acquisition dates: August 15th, 2016; September 24th, 2016; October 14th, 2016; November 13th, 2016; August 30th, 2017; September 19th, 2017; October 29th, 2017; and November 18th, 2017. 2.3. Field Data During 2016 and 2017, the Sanitation Laboratory sampled chlorophyll-a concentrations at seven monitoring points shown in Figure 1 monthly. The reference standards for the monitoring of bodies of water are set out in National Environmental Council Resolution No. 357 (CONAMA, 2005) and in the National Water Agency's National Sample Collection and Preservation Guide (ANA, 2011). The chlorophyll-a were obtained from water samples by the spectrophotometric analysis using a Hach DR 2800 Spectrophotometer. Samples were filtered, extracted and calculated according to colorimetric method (Marker et al., 1980). From a total of 168 samples available, 56 samples were used corresponding to the dry season. Field data campaigns were conducted on August 17th, 2016; September 21st, 2016; October 26th, 2016; November 23rd, 2016; August 18th, 2017; September 16th, 2017; October 28th, 2017; and November 25th, 2017. Considering that the field data sampling collecting date did not agree with the dates that Sentinel-2A overpassed the study area, we analysed all time windows available in the dry season, because it is the critical period during which eutrophication and the proliferation of phytoplankton, algae, cyanobacteria and aquatic plants occur. The number of match-ups along the period under study: 1 with one-day difference, 1 with two-days difference, 2 with three- days difference, 1 with seven-days difference, 1 with ten-days difference and 2 with twelve- days difference. 2.4. Chlorophyll-a concentration retrieval algorithms A variety of empirical algorithms have been developed and used to retrieve chlorophyll-a concentration in inland waters, where the spectral reflectance curves of waters with different chlorophyll-a concentrations are characterized by high absorptions in the blue and red bands and high reflectance in the green and red edge bands (Matthews, 2017; Ogashawara et al., 2017). The choice of the algorithms was based on a literature review in which the band ratio empirical algorithms found in Ha et al., 2017 (Chla-1: Equation 1), Page et al., 2018 (Chla-2: Equation 2) and Kuhn et al., 2019 (Chla-3: Equation 3) were selected. These algorithms include the green to blue band ratios and those including the red band and red edge band (Ha et al., 2017; Page et al., 2018; Kuhn et al., 2019). They were routinely applied to Sentinel-2A data and obtained the best performances in retrieval chlorophyll-a in lentic and lotic inland waters from regions with similar geographical and climatic features as those found in the study area. 퐵03 퐶ℎ푙푎 = 0.80 (푒푥푝 (0.35 ( ))) (1) 퐵04 휌 (퐵05)− 휌 (퐵04) 휌 (퐵05)− 휌 (퐵04) 2 퐶ℎ푙푎 = 14.039 + 86.115 ( 푟푐 푟푐 ) + 194.325 ( 푟푐 푟푐 ) (2) 휌푟푐(퐵05)+ 휌푟푐(퐵04) 휌푟푐(퐵05)+ 휌푟푐(퐵04) 2 푅푟푠(휆퐵02) 푅푟푠(휆퐵02) 푙표𝑔10(푐ℎ푙푎) = 0.2412 − 2.0546 (푙표𝑔10 ( )) + 1.1776 (푙표𝑔10 ( )) − 푅푟푠휆(퐵03) 푅푟푠휆(퐵03) 3 4 푅푟푠(휆퐵02) 푅푟푠(휆퐵02) 0.5538 (푙표𝑔10 ( )) + 0.4570 (푙표𝑔10 ( )) (3) 푅푟푠휆(퐵03) 푅푟푠휆(퐵03) Rev. Ambient. Água vol. 15 n. 2, e2488 - Taubaté 2020 6 Alessandro Rhadamek Alves Pereira et al. In this understanding, the following steps were performed in QGIS Desktop 3.4.5 software: i) Calculation of chlorophyll-a concentration as a function of the Chla-1, Chla-2 and Chla-3 equations in Sentinel-2A / L2A images (satellite-derived). The Sentinel-2A band selection (Table 1) has followed the proximity wavelength criteria closest to that defined by each empirical algorithm; ii) Listing of chlorophyll-a values at the seven monitoring points. Discrepancies between chlorophyll-a concentrations of punctual data, in situ (Chla-is) and satellite-derived (Chl-1, Chl-2, Chl-3), were quantified using statistical metrics, often intended for evaluation of remote-sensing algorithms, which in this case include the Pearson squared correlation or coefficient of determination (R²), the Root Mean Square Error (RMSE), and the Bias (Ha et al., 2017; Page et al., 2018; Kuhn et al., 2019). All data were analyzed using R 3.6.1 and Past 3.24 statistical softwares. The R² metric represents the linear consistency between the observations and the proportion of the variation explained by the linear regression, the RMSE measures the precision of the combinations and the absolute difference, which is sensitive to the extreme values, and the Bias determines the underestimation or overestimation of the calculated data, compared to field-measured data (Qin et al., 2017; Ansper and Alikas, 2019). A high R² value indicates a high degree of correlation between in situ observations and Sentinel-2A, while a low RMSE value indicates that Sentinel-2A observations resemble well with in situ observations, and a value close to zero for Bias suggests that there is no systematic underestimation or overestimation of Sentinel-2 and in situ data (Qin et al., 2017). 3. RESULTS AND DISCUSSION 3.1. Comparison of chlorophyll-a concentrations Table 2 shows the descriptive statistics of in situ chlorophyll-a (Chla-is) punctual concentration levels during the sampling period. In the Poti River, spatial variability is represented by the variation in the average concentrations of Chla-is, while the high standard deviation in the concentration levels of Chla-is indicates temporal variability. Table 2. Descriptive statistics of chlorophyll-a in situ punctual concentration (mg m³-1) in 2016 and 2017. Point / Year Mean Standard deviation Coefficient of Variation Minimum Maximum PT-00/16 17.75 15.68 0.88 5.46 38.22 PT-01/16 31.40 26.14 0.83 10.92 65.52 PT-02/16 32.76 31.21 0.95 5.46 76.44 PT-03/16 23.21 8.19 0.35 16.38 32.76 PT-04/16 39.59 21.09 0.53 27.30 70.98 PT-05/16 28.67 16.90 0.59 5.46 43.68 PT-06/16 27.30 24.82 0.91 5.46 60.06 PT-00/17 5.18 2.07 0.40 4.14 8.29 PT-01/17 10.36 7.94 0.77 4.14 20.72 PT-02/17 15.54 12.37 0.80 4.14 33.15 PT-03/17 9.32 7.84 0.84 4.14 20.72 PT-04/17 9.32 7.84 0.84 4.14 20.72 PT-05/17 10.36 4.14 0.40 8.29 16.58 PT-06/17 11.40 7.08 0.62 4.14 20.72 Rev. Ambient. Água vol. 15 n. 2, e2488 - Taubaté 2020 Retrieval and mapping of chlorophyll-a … 7 From the monthly in situ samples of chlorophyll-a, the average results obtained in 2016 were 28.67 mg m³-1, ranging from 5.46 mg m³-1, recorded at PT-00, to 76.44 mg m³-1, read at PT-02, both in August. In 2017, the average chlorophyll-a count was 10.21 mg m³-1, also varying in August at the same points, between 4.14 mg m³-1 and 33.15 mg m³-1, respectively. According to the data, annually the concentration of chlorophyll-a increases from August to December, peaking in November, and in 2017 there was a reduction of 36% in the concentration of chlorophyll-a in the study area. These results show a large spatiotemporal variation of chlorophyll-a in the dry season, depending on the location of the collection points, where the points that indicate the lowest and highest recurrent chlorophyll-a concentrations are PT-00 and PT-02. The influence of factors such as incipient environmental management, occupation of river margins, existence of clandestine connections of raw sewage in the rain drainage and the high evaporation of water, have contributed to the alteration of the limnological characteristics of the Poti River (Oliveira and Silva, 2014; Oliveira Filho and Lima Neto, 2018). In addition, in the dry season, the reduction in flow, width and depth favour the formation of natural barriers, such as meandering curves, rocky outcrops, alluvial deposits of pebbles to sands and river islands, cause the damming of Poti River waters (Lima and Augustin, 2014). From this perspective, natural and artificial barriers, in addition to the land-use change, are the most important structural determinants for the modification of the limnological characteristics of a watershed, as they create a lentic mosaic macrosystem, very different from the original lotic condition, favourable to the processes of eutrophication (Debastiani Júnior et al., 2016). These concentrations can be explained by the location of these points, as PT-00 is located in the least- inhabited region, with preserved riparian forest and without contributions from domestic and industrial effluents, while PT-02 is located at 850 m downstream from the Alegria Sewage Treatment Plant (Mendes-Câmara, 2011). Subsequently, the processing of the Chl-1, Chl-2 and Chl-3 equations was performed on Sentinel-2A / L2A images obtaining the values of chlorophyll-a at seven points. Considering that these algorithms also tend to vary in performance, because depending on the optical properties of the river and chlorophyll-a, temperature, nutrients and light may introduce classification errors, the performance of the applied algorithms was analyzed punctually in Sentinel-2 images available in the dry period. In total, four values of chlorophyll- a were used for each sampling point. The performances of the algorithms for the Poti River are summarized in Table 3. Considering a moderate correlation, with R² values equal or higher than 0.50, between the results of punctual quantitative agreement between in situ data and values obtained with each equation, overall, the empirical algorithm Chl-2, with seven values, obtained the best point performance compared to the algorithms Chl-1, with six values, and Chl-3, with four values. Therefore, according to this data, the relation between the bands B04 and B05 most indicated the retrieval of chlorophyll-a in the Poti River. In this sense, considering the Equation Chl-2, by Page et al. (2018), Figure 2 shows the graphs of the dynamics of the chlorophyll-a in situ (Chla-is) and satellite-derived (Chl-2) for 2016 (samples 1-28) and 2017 (samples 29-56). In the set of 56 samples, the Chl-2 algorithm shows an overestimation of concentrations, as indicated by Bias, and follows the tendency of chlorophyll-a to occur as pointed out by the in situ data. However, it is possible to observe the performance of the algorithm at different collection points along the river and realise that it can estimate the variation of chlorophyll-a concentration broadly and not more punctual. 3.2. Mapping of chlorophyll-a concentrations The mapping of chlorophyll-a concentrations was performed using the QGIS Desktop 3.4.5; when a clipping was generated referring to the study area, in the images resulting from Rev. Ambient. Água vol. 15 n. 2, e2488 - Taubaté 2020 8 Alessandro Rhadamek Alves Pereira et al. each calculated equation it was possible to spatially verify the occurrence and distribution of chlorophyll-a along the Poti River in the mentioned biennium. Maps derived from Sentinel-2A-L2A show details of the spatial variation of chlorophyll- a concentration, allowing easy identification of areas with high or no chlorophyll-a concentrations, and show that there is a common pattern between estimated and in situ data. At the same time, regardless of the algorithm used, the maps always show the stretch from Point PT-04 to the mouth of the Poti River, approximately 16 km long, as the area with a high concentrations of chlorophyll-a. Table 3. Comparison by point between estimated and in situ chlorophyll-a concentration (mg m³-1) in 2016 and 2017. Chl-1 Chl-2 Chl-3 Point / Year R² RMSE Bias R² RMSE Bias R² RMSE Bias PT-00/16 0.17 21.34 -16.51 0.54 16.26 0.68 0.41 21.35 -16.57 PT-01/16 0.00 37.70 -30.15 0.25 28.23 1.70 0.73 38.13 -30.70 PT-02/16 0.06 41.45 -31.41 0.03 30.10 6.17 0.59 41.83 -31.87 PT-03/16 0.75 22.97 -21.87 0.98 23.29 23.25 0.16 23.43 -22.30 PT-04/16 0.54 42.32 -38.14 0.45 44.40 27.15 0.25 42.74 -38.58 PT-05/16 0.65 30.93 -27.15 0.52 65.05 45.86 0.49 31.38 -27.68 PT-06/16 0.01 33.63 -25.85 0.01 38.39 24.74 0.01 34.08 -26.43 PT-00/17 0.96 4.37 -3.95 1.00 7.96 6.64 0.94 4.80 -4.42 PT-01/17 0.15 11.43 -9.12 0.20 14.80 13.35 0.46 11.78 -9.65 PT-02/17 0.05 17.85 -14.27 0.67 21.15 11.34 0.00 18.28 -14.80 PT-03/17 0.39 10.51 -8.04 0.22 20.70 19.38 0.26 10.93 -8.54 PT-04/17 0.85 10.45 -8.02 0.91 23.43 22.42 0.48 10.76 -8.41 PT-05/17 0.79 9.70 -9.03 0.95 27.34 26.91 0.01 10.20 -9.55 PT-06/17 0.29 11.83 -10.07 0.07 36.50 29.30 0.54 12.45 -10.74 Figure 2. Comparison between the Chla-2 and Chla-is indices in 2016 and 2017. Figure 3 shows the change in chlorophyll-a concentration at the beginning of the dry seasons of 2016 and 2017, calculated with data from the Chl-2 algorithm (Page et al., 2018), with emphasis on the section of Point PT-04 to the mouth of the Poti River in the months of Rev. Ambient. Água vol. 15 n. 2, e2488 - Taubaté 2020 Retrieval and mapping of chlorophyll-a … 9 August until November of each year. As can be seen in this figure, the high concentration of chlorophyll-a corresponds to red. Figure 3. Spatial distribution of chlorophyll-a concentration from August to November 2016 and from August to November 2017. 4. CONCLUSIONS This study is the first attempt to evaluate the use of Sentinel-2 in Poti River remote sensing. The results show that Sentinel-2 images have great potential for urban river remote sensing, as we were able to retrieve and map chlorophyll-a concentrations by means of routinely used empirical algorithms. The results generated by the Chl-1, Ha et al. (2017), Chl-2, Page et al. (2018), and Chl-3, Kuhn et al. (2019) equations show the need for calibration of the models used to simulate the Rev. Ambient. Água vol. 15 n. 2, e2488 - Taubaté 2020 10 Alessandro Rhadamek Alves Pereira et al. Poti River water components. Considering a moderate correlation between the results of punctual quantitative agreement between the in situ data and the values obtained with each equation, the empirical algorithm Chl-2 obtained a better punctual performance than the algorithms Chl-1 and Chl-3. The empirical algorithm Chl-2 shows a correlation has been established to identify the spatiotemporal variation of chlorophyll-a concentration along the Poti River broadly and not more punctually. The spatiotemporal distribution of chlorophyll-a in maps from Sentinel-2A images are consistent with the pattern of occurrence determined by the in situ data. Therefore, the MSI sensor proved to be a tool suitable for the detection and monitoring of chlorophyll-a concentration along the Poti River. In addition, it is recommended that a chlorophyll-a concentration monitoring system be implemented using a calibrated algorithm for the Poti River optical properties and Sentinel-2 data in order to improve the environmental management of the river. To enable the monitoring of water quality in urban rivers, especially in the tropical semiarid region of Brazil is a contribution to the conservation of the environment and the sustainable management of this water resource, as it will permit the verification of current and possible future conditions of eventual environmental, social and economic impacts. 5. REFERENCES ANA. Guia nacional de coleta e preservação de amostras: água, sedimento, comunidades aquáticas e efluentes líquidos. São Paulo: CETESB; Brasília: ANA, 2011. 326p. Available at: http://arquivos.ana.gov.br/institucional/sge/CEDOC/Catalogo/2012/GuiaNacionalDeCol eta.pdf Access: 05 oct. 2017. ANSPER, A.; ALIKAS, K. Retrieval of chlorophyll a from Sentinel-2 MSI data for the European Union Water Framework Directive reporting purposes. Remote Sensing, v. 11, n. 1, p. 64, 2019. https://doi.org/10.3390/rs11010064 BRASIL. Ministério do Meio Ambiente. Biomas. Brasília, 2017. Available at: http://mapas.mma.gov.br/i3geo/datadownload.htm. Access: 03 May 2019. CONAMA (Brasil). Resolução nº 357 de 17 de março de 2005. Dispõe sobre a classificação dos corpos de água e diretrizes ambientais para o seu enquadramento, bem como estabelece as condições e padrões de lançamento de efluentes, e dá outras providências. Diário Oficial [da] União: seção 1, Brasília, DF, n. 053, p. 58-63, 18 mar. 2005. COSTA, C. Aguapés são retirados do Rio Poti em Teresina após ação do MPF. G1 PI, Teresina, 10 de fevereiro de 2014. Available at: http://g1.globo.com/pi/piaui/noticia/2014/02/apos- quatro-meses-da-acao-do-mpf-aguapes-serao-retirados-do-rio-poti.html. Access: 03 nov. 2014. DEBASTIANI JÚNIOR, J. R.; NALIATO, D. A. O.; PERBICHE-NEVES, G.; NOGUEIRA, M. G. Fluvial lateral environments in Río de La Plata basin: effects of hydropower damming and eutrophication. Acta Limnologica Brasiliensia, v. 28, e26, 2016. http://dx.doi.org/10.1590/s2179-975x5516 ESA. Sentinel-2 Products Specification Document. France: Thales Alenia Space, 2018, 510p. Available at: https://sentinel.esa.int/documents/247904/685211/Sentinel-2-Products- Specification-Document. Access: 30 Aug. 2018. ESA. Copernicus Open Access Hub. 2019. Available at: https://scihub.copernicus.eu/dhus/#/home. Access: 15 Aug. 2019. Rev. Ambient. Água vol. 15 n. 2, e2488 - Taubaté 2020 Retrieval and mapping of chlorophyll-a … 11 ESPINDOLA, G. M.; CARNEIRO, E. L. N. C.; FAÇANHA, A. C. Four decades of urban sprawl land population growth in Teresina, Brazil. Applied Geography, v. 79, p. 73-83, 2017. https://doi.org/10.1016/j.apgeog.2016.12.018 ESTEVES, F. de A. Fundamentos de limnologia. 3. ed. Rio de Janeiro: Interciência, 2011. 790 p. HA, N. T. T.; THAO, N. T. P.; KOIKE, K.; NHUAN, M. T. Selecting the best band ratio to estimate chlorophyll-a concentration in a tropical freshwater lake using Sentinel 2A images from a case study of lake Ba Be (Northern Vietnam). International Journal of Geo-Information, v. 6, p. 290, 2017. https://doi.org/10.3390/ijgi6090290 IBGE. Clima do Brasil 1:500.000. Brasília, 2015. Available at: http://dados.gov.br/dataset/cren_climadobrasil_5000. Access: 14 Apr. 2018. IBGE. Brasil/Piauí/Teresina. Brasília, 2017. Available at: https://cidades.ibge.gov.br/brasil/pi/teresina/panorama. Access: 08 Feb. 2019. INMET. Normais Climatológicas do Brasil 1981-2010. Brasília, 2018. Available at: http://www.inmet.gov.br/portal/index.php?r=clima/normaisClimatologicas. Access: 14 Apr. 2018. JORGE, D. S. F.; LOBO, F. L. Aplicações do sensoriamento remoto em águas continentais - estudos de caso. In: BARBOSA, C. C. F.; NOVO, E. M. L. M.; MARTINS, V. S. (Eds.). Introdução ao sensoriamento remoto de sistemas aquáticos: princípios e aplicações. 1. ed. São José dos Campos, SP: INPE, 2019. p. 136-152. KUHN, C.; VALERIO, A. M.; WARD, N.; LOKEN, L.; SAWAKUCHI, H. O.; KAMPEL, M.; RICHEY, J.; STADLER, P.; CRAWFORD, J.; STRIEGL, R.; VERMOTE, E.; PAHLEVAN, N.; BUTMAN, D. Performance of Landsat-8 and Sentinel-2 surface reflectance products for river remote sensing retrievals of chlorophyll-a and turbidity. Remote Sensing of Environment, v. 224, p. 104-118, 2019. https://doi.org/10.1016/j.rse.2019.01.023 LIMA, I. M. M. F.; AUGUSTIN, C. H. R. R. Bacia hidrográfica do rio Poti: dinâmica e morfologia do canal principal no trecho do baixo curso. In: SIMPÓSIO NACIONAL DE GEOMORFOLOGIA, 10., 2014, Manaus. Anais[…] Manaus: SINAGEO; UFAM, 2014. v. 1. MARKER, A. F. H.; NUSCH, E. A.; RAI, H.; RIEMANN, B. The measurement of photosynthetic pigments in freshwaters and standardization of methods: conclusions and recommendations. Ergebnisse der Limnologie, v. 14, p. 91-106, 1980. MARTINS, V. S. Sistemas orbitais para monitoramento de ambientes aquáticos. In: BARBOSA, C. C. F.; NOVO, E. M. L. M.; MARTINS, V. S. (Eds.). Introdução ao sensoriamento remoto de sistemas aquáticos: princípios e aplicações. 1. ed. São José dos Campos, SP: INPE, 2019. p. 107-135. MATTHEWS, M. W. Bio-optical modeling of phytoplankton chlorophyll-a. In: MISHRA, D. R.; OGASHAWARA, I.; GITELSON, A. A. (Eds.). Bio-optical modeling and remote sensing of inland waters. 1. ed. Amsterdam: Elsevier, 2017. p. 157-188. https://doi.org/10.1016/B978-0-12-804644-9.00001-X MENDES-CÂMARA, F. M. Avaliação da qualidade da água do rio Poti na cidade de Teresina, Piauí. 2011. 162f. Tese (Doutor em Geografia) - Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista, Rio Claro, 2011. Rev. Ambient. Água vol. 15 n. 2, e2488 - Taubaté 2020 12 Alessandro Rhadamek Alves Pereira et al. MOUW, C. B.; GREB, S.; AURIN, D.; DIGIACOMO, P. M.; LEE, Z.; TWARDOWSKI, M.; BINDING, C.; HU, C.; MA, R.; MOORE, T.; MOSES, W.; CRAIG, S. E. Aquatic color radiometry remote sensing of coastal and inland waters: Challenges and recommendations for future satellite missions. Remote Sensing of Environment, v. 160, p. 15-30, 2015. https://doi.org/10.1016/j.rse.2015.02.001 OGASHAWARA, I.; MISHRA, D. R.; GITELSON, A. A. Remote sensing of inland waters: background and current state-of-the-art. In: MISHRA, D. R.; OGASHAWARA, I.; GITELSON, A. A. (Eds.). Bio-optical modeling and remote sensing of inland waters. 1. ed. Amsterdam: Elsevier, 2017. p. 1-24. https://doi.org/10.1016/B978-0-12-804644- 9.00001-X OLIVEIRA, L. N. de.; SILVA, C. E. da. Qualidade da água do rio poti e suas implicações para atividade de lazer em Teresina-PI. Revista Equador, v. 3, n. 1, p. 128-147, 2014. OLIVEIRA FILHO, A. A. de.; LIMA NETO, I. E. Modelagem da qualidade da água do rio Poti em Teresina (PI). Engenharia Sanitária Ambiental, v.23, n.1, 2018. http://dx.doi.org/10.1590/s1413-41522017142354 PAGE, B. P.; KUMAR, A.; MISHRA, D. R. A novel cross-satellite based assessment of the spatio-temporal development of a cyanobacterial harmful algal bloom. International Journal of Applied Earth Observation and Geoinformation, v. 66, p. 69-81, 2018. https://doi.org/10.1016/j.jag.2017.11.003 PEREIRA-SANDOVAL, M.; URREGO, E. P.; RUIZ-VERDÚ, A.; TENJO, C.; DELEGIDO, J.; SÒRIA-PERPINYÀ, X.; VICENTE, E.; SORIA, J.; MORENO, J. Calibration and validation of algorithms for the estimation of chlorophyll-a concentration and Secchi depth in inland waters with Sentinel-2. Limnetica, v. 38, n. 1, p. 471-487, 2019. https://dx.doi.org/10.23818/limn.38.27 PINARDI, M.; BRESCIANI, M.; VILLA, P.; CAZZANIGA, I.; LAINI, A.; TÓTH, V.; FADEL, A.; AUSTONI, M.; LAMI, A.; GIARDINO, C. Spatial and temporal dynamics of primary producers in shallow lakes as seen from space: Intra-annual observations from Sentinel-2A. Limnologica, v. 72, p. 32-43, 2018. https://doi.org/10.1016/j.limno.2018.08.002 PRASAD, S.; SALUJA, R.; J. K. GARG, J. K. Modeling chlorophyll-a and turbidity concentrations in river Ganga (India) using Landsat-8 OLI imagery. In: Earth Resources and Environmental Remote Sensing/GIS Applications, 8., 2017, Warsaw, Poland. SPIE Proceedings[…] Available at: https://doi.org/10.1117/12.2304034. Access: 14 Apr. 2018. QIN, P.; SIMIS, S.G.H.; TILSTONE, G.H. Radiometric validation of atmospheric correction for MERIS in the Baltic Sea based on continuous observations from ships and AERONET-OC. Remote Sensing of Environment, v. 200, p. 263-280, 2017. https://doi.org/10.1016/j.rse.2017.08.024 SANTOS, L. Aguapés voltam a tomar conta da superfície do rio Poti. Portalodia, 07 Nov. 2017. Available at: https://www.portalodia.com/noticias/teresina/aguapes-voltam-a- tomar-conta-da-superficie-do-rio-poti-308858.html. Access: 05 Mar. 2018. SINERGISE. Sentinel 2 EO products. Available at: https://www.sentinel- hub.com/develop/documentation/eo_products/Sentinel2EOproduct. Access: 04 Sep. 2018. Rev. Ambient. Água vol. 15 n. 2, e2488 - Taubaté 2020 Retrieval and mapping of chlorophyll-a … 13 TOMING, K.; KUTSER, T.; LAAS, A.; SEEP, M.; PAAVEL, B.; NÕGES, T. First experiences in mapping lake water quality parameters with Sentinel-2 MSI imagery. Remote Sensing, v. 8, n. 8, p. 640, 2016. https://doi.org/10.3390/rs8080640 VARGAS, R. R.; BARROS, M. S.; SAAD, A. R.; ARRUDA, R. O. M.; AZEVEDO, F. D. Assessment of the water quality and trophic state of the Ribeirão Guaraçau Watershed, Guarulhos (SP): a comparative analysis between rural and urban areas. Revista Ambiente & Água, v. 13, n. 2, 2018. http://dx.doi.org/10.4136/ambi-agua.2170 Rev. Ambient. Água vol. 15 n. 2, e2488 - Taubaté 2020 Ambiente & Água - An Interdisciplinary Journal of Applied Science ISSN 1980-993X – doi:10.4136/1980-993X www.ambi-agua.net E-mail: [email protected] Variability in phytoplankton community structure and influence on stabilization pond functioning ARTICLES doi:10.4136/ambi-agua.2507 Received: 11 Dec. 2019; Accepted: 19 Feb. 2020 Emmanuel Bezerra D'Alessandro1 ; Ina de Souza Nogueira2 ; Nora Katia Saavedra del Aguila Hoffmann3* 1Departamento de Química. Instituto de Química. Laboratório de Métodos de Extração e Separação. Universidade Federal de Goiás (UFG), Campus Samambaia, Alameda Palmeiras, Chácaras Califórnia, S/N, CEP: 74045-155, Goiânia, GO, Brazil. E-mail: [email protected] 2Departamento de Botânica. Instituto de Ciências Biológicas. Laboratório de Meio Ambiente e Recursos Hídricos. Universidade Federal de Goiás (UFG), Avenida Esperança, S/N, CEP: 74690-900, Campus Samambaia, Goiânia, GO, Brazil. E-mail: [email protected] 3Departamento de Hidráulica e Saneamento. Programa de Pós-graduação em Engenharia Ambiental e Sanitária. Escola de Engenharia Civil e Ambiental da Universidade Federal de Goiás (EECA-UFG), Avenida Universitária, n° 1488, CEP: 74605-220, Quadra 86, Setor Universitário, Goiânia, GO, Brazil *Corresponding author. E-mail: [email protected] ABSTRACT Density of phytoplankton in stabilization ponds influences treatment performance. The study hypothesized that the phytoplankton community structure varies according to local and temporal changes and consequently influences the treatment of the effluent. Phytoplankton community structure in facultative and maturation ponds in central Brazil was analyzed to provide guidance on system operation and maintenance. Further, species density, abundance, diversity, richness, dominance and beta diversity were measured. The efficiency of the treatment was evaluated based on Biochemical Oxygen Demand (BOD). Additionally, a Canonical Correspondence Analysis (CCA) was used to investigate how physical and chemical variables influenced the composition of the most abundant species in the dry and rainy seasons and the microalgae that were most related to the removal of BOD. One hundred and sixty-eight taxa were recorded, and the most abundant classes in both ponds were Chlorophyceae and Cyanophyceae (40% potentially toxic). The maturation pond had greater adaptability in the rainy season, while the facultative pond was more flexible in the dry season. The best period of growth varied among species. In both ponds, Chlorella minutissima was the one which most contributed to the optimization of the treatment. Thus, identifying phytoplankton species and relating them to water quality parameters and weather can help to understand the ecological dynamics of wastewater treatment and provide useful information for the operation and maintenance of stabilization ponds. Keywords: cyanobacteria, diversity, wastewater. Variabilidade na estrutura das comunidades fitoplanctônicas e influência no funcionamento de lagoa de estabilização RESUMO A densidade do fitoplâncton em lagoas de estabilização influencia no desempenho do This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 Emmanuel Bezerra D'Alessandro et al. tratamento. A hipótese foi que a estrutura da comunidade fitoplanctônica varia de acordo com as mudanças locais e temporais e, consequentemente, influencia o tratamento do efluente. Foram analisados a estrutura da comunidade fitoplanctônica em lagoas facultativas e de maturação no Brasil central para fornecer orientações sobre a operação e manutenção do sistema. Foram medidas a densidade, abundância, diversidade, riqueza, dominância e diversidade beta das espécies. A eficiência do tratamento foi avaliada com base na Demanda Bioquímica de Oxigênio (DBO). Adicionalmente, foi realizada uma Análise de Correspondência Canônica (CCA) para investigar como variáveis físicas e químicas influenciaram a composição das espécies mais abundantes nas estações seca e chuvosa, e as microalgas mais relacionadas à remoção de DBO. Foram registrados 168 táxons e as classes mais abundantes em ambas as lagoas foram Chlorophyceae e Cyanophyceae (40% potencialmente tóxicas). A lagoa de maturação possui maior adaptabilidade na estação chuvosa, enquanto a lagoa facultativa foi mais flexível na estação seca. O melhor período de crescimento variou entre as espécies. Em ambas as lagoas, a Chlorella minutissima foi a que mais contribuiu para a otimização do tratamento. Assim, identificar espécies de fitoplâncton e relacioná-las com parâmetros de qualidade da água e a sazonalidade pode ajudar a entender a dinâmica ecológica do tratamento de águas residuais e fornecer informações úteis para a operação e manutenção de lagoas de estabilização. Palavras-chave: águas residuárias, cianobactéria, diversidade. 1. INTRODUCTION Stabilization ponds are artificial environments used for sewage treatment. An increase in nutrients in these ponds promotes phytoplankton overgrowth, which can risk public health, since some species release toxic substances that can bioaccumulate and cause cancer. Species evenness varies in such ponds; for example, cyanobacteria can dominate in either stabilization or maturation ponds (Aquino et al., 2011). The efficiency of the stabilization ponds is due to several factors such as temperature, hydraulic retention time, depth, bacteria and algae. In the case of algae in a stabilization pond, algal growth and nutrient assimilation are not only affected by nutrient viability, as they also depend on complex interactions between physical factors such as pH, light intensity, temperature, wind, solar radiation (Von Sperling, 2002) and biotic factors such as algal density (Lau et al., 1995). Phytoplankton in stabilization ponds is essential for oxygen production required for organic matter degradation (Pastich et al., 2016). The phytoplankton community is involved in many ecosystem processes of inland, estuarine, and marine waters. They also are good bioindicators (Amengual-Morro et al., 2012). Branco et al. (1963) recorded 45 algae genera useful for wastewater treatment, while D'Alessandro et al. (2015) analyzed the efficiency of nutrient removal by algae. However, studies on phytoplankton communities of stabilization ponds are still scarce. Chlorophyceae is the most speciose algae group in stabilization ponds, usually followed by Euglenophyceae or cyanobacteria (Soldatelli and Schwarzbold, 2012; Gani et al., 2011). Additionally, some species commonly found in environments rich in organic matter also occur in stabilization ponds, such as Chlamydomonas, Euglena, Navicula, Synedra, Oscillatoria, and Phormidium (Sen et al., 2013). Thereby and Granado (2004) recorded Chlorella vulgaris as dominant in the winter and less abundant in other seasons in a stabilization pond. There are plenty of studies on algae and cyanobacteria focusing on limnological variables. However, little is known about how biotic and abiotic variables of stabilization ponds influence the phytoplankton community, despite the importance of algae to the functioning of these ecosystems. Rev. Ambient. Água vol. 15 n. 2, e2507 - Taubaté 2020 Variability in phytoplankton community structure and influence … 3 The hypothesis of the present research was that the structure of the phytoplankton community varies according to local and temporal changes and, consequently, influences the treatment of the effluent. To test this, species density, abundance, diversity, richness, dominance, and beta diversity of the phytoplankton community were analyzed. How physical and chemical variables influenced the composition of the most abundant species in the dry and rainy seasons and the microalgae that were most related to the removal of Biochemical Oxygen Demand (BOD) were also explored. The results helped to identify the microalgae which are better fitted for wastewater treatment in stabilization ponds, and thus provide guidance for system operation and maintenance of the ponds. 2. MATERIALS AND METHODS 2.1. Study sites This study was conducted in facultative and maturation pond of the module A of the wastewater treatment plant of Trindade, Goiás, central Brazil (16°39'09'' S; 49°31'50'' W) during six months spanning rainy and dry seasons (September through December 2010, April and May 2011). The plant has an average flow rate of 161.6 L s-1, and BOD (biochemical oxygen demand) removal efficiency of 84%. The facultative pond studied has an area of 27,000 m2, depth of 1.25 m, a volume of 33,750 m3, and HRT (hydraulic retention time) of 4.8 days. The maturation pond has an area of 13,975 m2, 1.25 m of depth, volume of 17,468.75 m3, and 2.5 days of HRT. 2.2. Sampling and species identification To choose sampling points, pond depth was first measured using a measuring tape attached to a rigid rod on a boat at points F1, F2, F3, M1, and M2 (Figure 1). In the facultative pond, depth was measured at three-points equidistant to the margin, one at the beginning (F1) at 90 m from pond entrance, one in the middle (F2) at 180 m from pond entrance, and another at the end of the lagoon (F3) 270 from the entrance. Similarly, depth was measured at two points equidistant to the margin, one at the beginning (M1) 70 m from the entrance of the maturation pond and another at the end (M2) 150 m from the entrance. Facultative pond F1 F2 F3 90 m 90 m 90 m 90 m F2S (0.10 m) Effluent F2M (0.85 m) Influent F2B (1.50 m) Maturation pond M1 M2 70 m 80 m 65 m M1S (0.10 m) M2S (0.10 m) Effluent M1M (0.65 m) M2M (0.65 m) Influent M1B (1.10 m) M2B (1.10 m) Figure 1. Sampling points in the facultative and maturation ponds of module A of the wastewater treatment plant of Trindade, Goiás, central Brazil. S: surface; M: middle; B: bottom. Samplings were made using a 5 L Van Dorn bottle from 09h40 to 11h00 am in the facultative pond. Using a boat, samplings were collected along the vertical profile at point F2 (surface, middle, and bottom approximately 20 cm above the mud). In the maturation pond, samplings were made from 10h50 to 12h00 am at points M1 and M2 at three depths (surface, Rev. Ambient. Água vol. 15 n. 2, e2507 - Taubaté 2020 4 Emmanuel Bezerra D'Alessandro et al. middle, and bottom) at each point. The maturation pond had two collection points due to the higher concentration of chlorophyll than the facultative pond. The physical, chemical and biological parameters of the maturation pond were obtained by averaging them at two points (M1 and M2) and their depths. Qualitative samples of phytoplankton were stored in transparent 100 mL glass bottles and fixed with 4% formaldehyde. Live samples were also analyzed. Species identification was based on morphological and morphometric characteristics analyzed under an inverted Olympus microscope CKX41, coupled with a camera and a Cell D® program. Nomenclature for classes followed Van Den Hoek et al. (2008); Cyanobacteria was identified using Komárek and Anagnostidis (2005); Chlorophyceae using Komárek and Fott (1983), D’Alessandro and Nogueira (2017); Euglenophyceae Nogueira (2007); for other classes Bicudo and Menezes (2006). Quantitative samples were placed in 100 mL amber glass bottles, fixed with Lugol (Bicudo and Menezes, 2006) and analyzed under an inverted microscope Olympus CKX41 using a settling chamber following Utermöhl (1958). Cells were counted in 10 to 15 randomly chosen fields (Uehlinger, 1964). Due to high concentration of organisms, 1:2 and 1:3 dilutions were used. To enhance quantification strategy, were counted a maximum of 250 individuals (unicellular, colonial, coenobium, trichome, and filamentous) of the second most common species. Were adopted a minimum counting efficiency of 97%, which is the probability that the required number of individuals have been counted and new species are less likely to appear (Pappas and Stoermer, 1996). Thus, counting error is less than 20% at a significance level of 95%. Here, were considered a cell, colony, coenobium colony, trichome, or filament as an individual. 2.3. Environmental variables To calculate the euphotic zone, the Secchi disk value was multiplied by three. Water temperature and dissolved oxygen were measured using an oximeter (Thermo Scientific/Orion 5 stars). Ammonia samples were analyzed by the direct method Nessler following Silva and Oliveira (2001). It was also measured pH (potentiometric method), conductivity (CND; potentiometric), biochemical oxygen demand (BOD; dilution), chemical oxygen demand -3 (COD; colorimetric), nitrate (NO3; UV), orthophosphate (PO4 ; ascorbic acid), and total phosphorus (TP; ascorbic acid) following APHA et al. (1998). 2.4. Community structure parameters The classification of size fractions for the most abundant species followed Sieburth et al. (1978). Were calculated species diversity using the Shannon (1948) index based on species density, and the evenness index of Pielou (1966). Species richness was measured in each quantitative sample. Abundant species were those with more than 0.8% abundance at each sampling point. Dominant species in each sampling point were determined following Lobo and Leighton (1986). Were calculated Whittaker’s (1972) beta diversity index (βW) to measure compositional turnover between ponds based on qualitative data. 2.5. Data analysis A Canonical Correspondence Analysis (CCA) was used to test how abiotic variables and seasonality influenced the composition of the most abundant species. The significance of the model was tested using Monte Carlo randomization with 999 runs. 3. RESULTS AND DISCUSSION 3.1. Characteristics of ponds Rev. Ambient. Água vol. 15 n. 2, e2507 - Taubaté 2020 Variability in phytoplankton community structure and influence … 5 Both ponds had working depths of 1.25 m, a higher volume than initially designed, probably because module C was deactivated. Thus, part of the volume of module A was directed to other two modules, changing their depths. Also, depth changed considerably during the sampling period, but the average for the maturation and facultative ponds were 1.74 and 1.36 m, respectively. Depth decreased in October (early rainy season) compared to September, likely because one of the pumping stations (“Bruacas”) was broken and did not release sewer to the treatment plant, changing flow rate. The increase in depth in both ponds in November and December 2010 was due to module A’s structure, high rainfall, and increased flow rate. The variation in depth of stabilization ponds in the wastewater treatment plant of Parque Atheneu, Goiás, Brazil was related to rainfall and likely illegal release of rainwater to sewage (Martins, 2003). Shammas et al. (2009) point out evaporation of pond water is usually insignificant, except in places with dry and warm weather, such as the study site. The same authors states that evaporation rate varies with temperature, atmospheric pressure, wind speed, and salt content of the water. The euphotic zone of the stabilization pond varied throughout the sampling period. However, the photic zone of the facultative pond did not vary as much as in the maturation pond, probably due to the pond’s size. The greatest depth recorded in both ponds was in November (1.85 m in the facultative, and 1.40 m in the maturation pond), whereas the deepest euphotic zone was recorded in September (0.38 m and 0.17 m, respectively) and the shallowest in November (0.13 m and 0.12 m, respectively). However, the facultative pond had the shallowest zone in October, December, April and May. 3.2. Phytoplankton community structure One hundred and sixty-eight taxa were found belonging to six divisions and seven classes (Cyanophyceae, Chlorophyceae, Euglenophyceae, Dinophyceae, Bacillariophyceae, Prasinophyceae, and Cryptophyceae (Figure 2), of which 121 taxa were recorded in the facultative and 152 in the maturation pond. The most speciose class in both ponds was Chlorophyceae, followed by Euglenophyceae and Cyanophyceae. These classes have different life history strategies such as their buoyancy mechanism, which may explain their high diversity and abundance. Previous studies also found dominance of Euglenophyceae instead of Chlorophyceae, due to higher concentration of organic matter (Mahapatra et al., 2013). The highest phytoplankton density in both ponds was recorded on the surface. This happened in September in the facultative pond (14,076,303 ind mL-1), while in the maturation pond it was in October (12,462,508 ind mL-1). Species density increased in the dry season and decreased in the rainy season, due to dilution. Rev. Ambient. Água vol. 15 n. 2, e2507 - Taubaté 2020 6 Emmanuel Bezerra D'Alessandro et al. Figure 2. Proportional species richness of phytoplankton per class in the facultative ( ) and maturation ( ) ponds of module A in Trindade wastewater treatment plant, Goiás, central Brazil. The highest phytoplankton densities ever recorded were observed in the stabilization ponds: 14 x 106 ind mL-1 in the facultative and 12.4 x 106 in the maturation pond. The species densities in wastewater treatment plants were 7 x 106 ind mL-1 in Parque Atheneu, Goiás (Martins, 2003), 9 x 105 cel mL-1 in Novo Horizonte, São Paulo (Falco, 2005), 3.8 x 106 ind mL-1 in Jacupiranga, São Paulo (Casali, 2008), 5.6 x 105 ind mL-1 in Biossistemas Integrados, Espírito Santo (Delazari-Barroso, 2009), and 4.2 x 105 ind mL-1 in UCS, Rio Grande do Sul (Soldatelli and Schwarzbold, 2012). The dominant species was Synechocystis sp. (cyanobacteria), which composed on average 75% of the density in the facultative and 83% in the maturation pond. Additionally, other algae and cyanobacteria were abundant during the study, such as Chlorella vulgaris, Chlorella minutissima, Closteriopsis acicularis, Merismopedia tenuissima, and Synechococcus sp. (Figure 3). Florentino et al. (2019) evaluation of algal diversity in stabilization pond systems treating domestic wastewater showed that the genera Euglena and Chlorella were present in relatively high frequencies in five of the six effluents analyzed. Figure 3. Relative abundance of species with higher density throughout the study, in the facultative and maturation pond of the module A, wastewater treatment plant of Trindade. ( ) Chlorella vulgaris; ( ) Chlorella minutissima; ( ) Closteriopsis acicularis; ( ) Merismopedia tenuissima; ( ) Synechococcus sp.; ( ) Synechocystis sp.; ( ) others. The abundance of Synechocystis sp. decreased in November and December 2010, which allowed the increase in abundance of C. acicularis. In April and May 2011, the abundance of C. minutissima increased. Seasonality affected both ponds similarly. The most abundant species were part of the nanoplankton, except for C. acicularis, which is microplankton. The possible cause of the high abundance of these algae and cyanobacteria was their great capacity to reproduce and absorb nutrients in stabilization ponds. Due to these characteristics, the cyanobacteria M. tenuissima was one of the most abundant species in the Parque Atheneu Stabilization Ponds, Goiás, BR (Martins, 2003), whereas Planktothrix isothrix as the most abundant in Barbalha, Ceará, BR (Aquino et al., 2011). A previous study found a high cyanobacteria density in the maturation pond, due to its morphometric parameters and high nutrient availability. A similar situation was found with Synechocystis sp. occurring in a higher abundance in the maturation than in the facultative pond during the whole study, except for December. Cyanobacteria tend to become dominant in turbid water because they are superior competitors at low light intensity, and once their high biomass has created a turbid environment, other phytoplankton species compete less effectively. Eland et al. (2019) determined more variation was seen between the systems waste stabilisation ponds Rev. Ambient. Água vol. 15 n. 2, e2507 - Taubaté 2020 Variability in phytoplankton community structure and influence … 7 than between different stages in the treatment processes for both eukaryotic and cyanobacterial communities. Chlorella species and Planktophrix cyanobacteria dominated both treatment systems. Species diversity, evenness, richness, and dominance were, on average, higher in the rainy than in the dry season in the facultative pond. The opposite pattern was observed in the maturation pond, probably due to differences in pond structure. Species diversity increased from October to December in both ponds, probably due to increased rainfall, which carried particles of suspended solids into the pond, reducing the euphotic zone and decreasing dissolved oxygen concentration, favoring new species, especially flagellates (Riediger et al., 2015), such as Chlamydomonas sp., Chilomonas sp., Chlorogonium sp., and Collodictyon sp. because, these species are heterotrophic and do not need light to produce metabolites. These heterotrophic algae have high potential to reduce cyanobacterial blooms (Kobayashi, 2013). The most speciose division in stabilization ponds is usually Chlorophyte, being Chlorella the most abundant genus. Chlorella is a microalgae widely used in industry, mainly for the production of biodiesel, polyunsaturated fatty acids (PUFAS), omega-3, lutein and other antioxidants. Therefore, the effluent from the stabilization ponds of our study site can be used as a nutrient medium for cultivating Chlorella, making the production of bioproducts viable (Abdel-Raouf et al., 2012), as implemented by other studies (Dahmani et al., 2016). The most common cyanobacteria genera in stabilization ponds are Oscillatoria and Microcystis, and common algae are Chlamydomonas, Euglena, Chlorella, Scenedesmus, and Micractinium. These algae were recorded in our study site and could potentially be used in biotechnological applications. The genera Aphanocapsa, Phormidium, Planktothrix, Pseudanabaena, Synechocystis, and Synechococcus recorded in the study site are considered potentially toxic. Merismopedia tenuissima can also produce cyanotoxins of microcystin type. However, cyanobacteria are not only ones to produce toxins, the algae Euglena granulata, E. clavata and E. anabaena found in the study site can produce toxins (Zimba et al., 2017). Beta-diversity (βW) describes the turnover or change in species identities along space. It is a measure of difference in species composition between local communities. Thereby, βW in the facultative pond was high in September (20.7) and low in October (12), whereas it was high in April (20.2) and lower in October (8.6) in the maturation pond. Both ponds had relatively low βW, indicating a low turnover in the phytoplankton community, i.e., ponds have high similarity (Schuster et al., 2015) and environments with high productivity can present low βw (Zorzal- Almeida et al., 2017). The maturation pond had higher βW in the rainy season, whereas it was higher in the dry season in the facultative pond. Increase βW in the maturation pond (Nov. – Apr.) was mainly due to Chlorophyceae phytoflagellates, such as Chlamydomonas and Chlorogonium. 3.3. Species-environment relationship The most frequent species could be divided into four groups regarding their response to environmental variables. Species of Group I occurred in September (end of the dry season), Group II in October (late dry and early rainy season), Group III in November and December (mid rainy), and Group IV in April (late rainy and early dry season) and May (early dry). C. minutissima had higher relationship in Group IV, while C. acicularis in Group III and the remaining species in Groups I and II (Figure 4a). The variables most correlated with Axis 1 were HRT and temperature, whereas BOD, CND, and ammonia were most correlated with Axis 2. Correlations between Monte Carlo parameters were higher than 0.98 for Axes 1 and 2 for both ponds (Table 1), i.e., there is not only a single dominant variable that determines the relationship between species and environment. Rev. Ambient. Água vol. 15 n. 2, e2507 - Taubaté 2020 8 Emmanuel Bezerra D'Alessandro et al. The analysis showed the same groups for the maturation pond (Figure 4b). The variables most correlated with Axis 1 were ammonia, temperature, euphotic zone, and HRT, while COD, DO, CND, and euphotic zone were most correlated with Axis 2 (Table 1). Figure 4. Ordination diagram showing the result of CCA for the relationship between species composition and environmental variables measured in the facultative (a) and maturation (b) pond. For legend see material and methods. Table 1. Summary table of showing the results of CCA. Loadings, relative eigenvalues, and p value for the model obtained with Monte Carlo randomizations in the facultative and maturation pond. Facultative Pond Maturation Pond Axis 1 Axis 2 Axis 1 Axis 2 Explicability Eigenvalues 0.38 0.21 0.42 0.24 % of Variance 57 31 56 32 Corr. of Variables Eigenvectors Eigenvectors Eigenvectors Eigenvectors DO 0.11 -0.42 -0.23 0.76* Temp. -0.63* 0.50 -0.80* -0.03 pH -0.25 -0.38 -0.53 0.53 CND 0.11 -0.71* 0.56 0.75* COD 0.10 -0.53 0.46 0.80* Orthophosphate 0.19 0.48 -0.23 -0.47 Ammonia 0.39 -0.69* 0.94* -0.09 Flow 0.56 -0.02 0.50 -0.33 HRT -0.64* -0.01 -0.60* 0.31 BOD 0.40 -0.76* 0.53 -0.37 Euphotic zone -0.29 -0.57 0.70* 0.68* Sp x Environa 0.995 0.987 0.999 0.990 *correlation coefficients important for axes building. aMonte Carlos Correlation, Species x Environmental (p = 0.001). The density of the most abundant species varied seasonally. Previous studies (Reynolds, 2006) also found a seasonal variation in species abundance of algae that track environmental change throughout the year. In this same study, Chlorella was tolerant to stratification and sensitive to low nutrient concentration. Species dominance patterns can change throughout the Rev. Ambient. Água vol. 15 n. 2, e2507 - Taubaté 2020 Variability in phytoplankton community structure and influence … 9 day according to changes in physical and chemical variables (Bernal et al., 2008). In the facultative pond, C. vulgaris occurred in October and September when stratification was more pronounced and the euphotic zone was greater. In both ponds, C. minutissima was better adapted to the dry season, higher concentrations of ammonia and BOD, and smaller HRT. Thus, this species may be promising to be used in wastewater treatment, due to its high rate of nutrient uptake. Also, this species was less affected by euphotic zone than M. tenuissima, showing that the latter can be heterotrophic or mixotrophic, while M. tenuissima is autotrophic. Species of the genus Synechococcus prefer homogeneous habitats, are sensitive to low light, dependent on the autotrophic system. High rainfalls tend to homogenize ponds. Thus, the abundance of Synechococcus sp. was predicted by October (early rainy season) and euphotic zone. On the other hand, Merismopedia prefer high ammonia concentration. Consequently, M. tenuissima was more affected by ammonia in our study. Generally, cyanobacterial blooms can be avoided by decreasing the phosphorus concentration at the site (Fastner et al., 2016). In this study the cyanobacteria were more influenced by the euphotic zone. Thus, to avoid cyanobacterial blooms in stabilization ponds, this variable must also be taken into account and not only the concentration of phosphorus. C. acicularis was more abundant in the months of high rainfall, possibly due to the increase of temperature, HRT and dilution of toxic substances of the sewage (e.g., ammonium and metals), which can influence phytoplankton growth (Reynolds, 2006). Therefore, environmental variables influence phytoplankton species distribution, diversity, abundance, and density in stabilization ponds, which can affect treatment efficiency. Species of the genus Synechococcus prefer homogeneous habitats, are sensitive to low light, dependent on the autotrophic system. High rainfalls tend to homogenize ponds. Thus, the abundance of Synechococcus sp. was predicted by October (early rainy season) and the euphotic zone. On the other hand, Merismopedia prefer high ammonia concentration. Consequently, M. tenuissima was more affected by ammonia in our study. Generally, cyanobacterial blooms can be avoided by decreasing the phosphorus concentration in the site (Fastner et al., 2016). In this study, the cyanobacteria were more influenced by the euphotic zone. Thus, to avoid cyanobacterial blooms in stabilization ponds, this variable must also be taken into account and not only the concentration of phosphorus. 4. CONCLUSION In conclusion, our study showed that stabilization ponds had low alpha- and beta diversity, despite having 168 taxa. However, beta diversity was higher in the rainy season in the maturation pond and in the dry season in the facultative pond. About 40% of the cyanobacteria recorded are potentially toxic. Thus, not only cyanobacteria, but also cyanotoxins launched in the ponds after treatment should be quantified. Except for C. acicularis, the most abundant cyanobacteria and algae in the ponds were nanoplankton, with C. minutissima the most important species for sewage treatment. This species has a high growth rate, higher contact surface of the cell, and mixotrophy and/or heterotrophy. Thus, identifying phytoplankton species and relating them to water quality parameters and weather can help to understand the ecological dynamics of wastewater treatment and provide useful information for the operation and maintenance of stabilization ponds. 5. REFERENCES ABDEL-RAOUF, N.; AL-HOMAIDAN, A. A.; IBRAHEEM, I. B. M. Microalgae and wastewater treatment. Saudi Journal Biological Sciences, v. 19, p 257–275, 2012. https://dx.doi.org/10.1016/j.sjbs.2012.04.005 Rev. Ambient. Água vol. 15 n. 2, e2507 - Taubaté 2020 10 Emmanuel Bezerra D'Alessandro et al. AMENGUAL-MORRO, C.; MOYÀ NIELL, G.; MARTÍNEZ-TABERNER, A. Phytoplankton as bioindicator for waste stabilization ponds. Journal of Environmental Management, v. 95, p. S71–S76, 2012. https://dx.doi.org/10.1016/j.jenvman.2011.07.008 APHA; AWWA; WEF. Standard Methods for the Examination of Water and Wastewater. 20. ed. Washington, 1998. AQUINO, E. P.; OLIVEIRA, E. C. C.; FERNANDES, U. L.; LACERDA, S. R. Fitoplâncton de uma Lagoa de Estabilização no Nordeste do Brasil. Brazilian Journal of Aquatic Science Technology, v. 15, p. 71–77, 2011. https://dx.doi.org/10.14210/bjast.v15n1.p71- 77 BERNAL, C. B.; VÁZQUEZ, G.; QUINTAL, I. B.; BUSSY, A. L. Microalgal dynamics in batch reactors for municipal wastewater treatment containing dairy sewage water. Water Air & Soil Pollution, v. 190, p. 259–270, 2008. https://dx.doi.org/10.1007/s11270-007- 9598-3 BICUDO, C. E. M.; MENEZES, M. Gênero de algas de águas continentais do Brasil. São Carlos: Rima, 2006. BRANCO, S. M.; BRANCO, W. C.; LIMA, H. A. S.; MARTINS, M. T. Identificação e importância dos principais gêneros de algas de interesse para o tratamento de águas e esgotos. São Carlos, 1963. CASALI, S. P. Variabilidade temporal da comunidade fitoplanctônica em lagoas facultativas de dois sistemas de tratamento de esgotos com diferentes configurações (Baixo Ribeira de Iguape, SP). 2008. Dissertação (Mestrado em Hidráulica e Saneamento) - Universidade de São Paulo, São Carlos, 2008. D’ALESSANDRO, E. B.; SAAVEDRA, N. K.; SANTIAGO, M. F.; D’ALESSANDRO, N. C. O. Influence of seasonality in stabilization ponds. Ingeniería del agua, v. 19, p. 193– 209, 2015. https://dx.doi.org/10.4995/ia.2015.3418 D’ALESSANDRO, E. B.; NOGUEIRA, I. D. E. S. Algas planctônicas flageladas e cocoides verdes de um lago no Parque Beija-Flor, Goiânia, GO, Brasil. Hoehnea, v. 44, p. 415– 430, 2017. https://dx.doi.org/10.1590/2236-8906-84/2016 DAHMANI, S.; ZERROUKI, D.; RAMANNA, L. Cultivation of Chlorella pyrenoidosa in outdoor open raceway pond using domestic wastewater as medium in arid desert region. Bioresource Technology, v. 219, p. 749–752, 2016. https://dx.doi.org/10.1016/j.biortech.2016.08.019 DELAZARI-BARROSO, A.; OLIVEIRA, F. F.; MARQUES, M. A. M. Avaliação temporal do fitoplâncton na lagoa de polimento de uma estação de tratamento de esgoto do tipo biossistemas integrados, em Alto Caxixe, Venda Nova do Imigrante, ES, Brasil. Revista Científica Faesa, v. 5, p. 7–16, 2009. ELAND, L. E.; DAVENPORT, R. J.; SANTOS, A. B.; MOTA FILHO, C. R. Molecular evaluation of microalgal communities in full-scale waste stabilization ponds. Environmental Technology, v. 40, n. 15, p. 1969-1976, 2019. https://doi.org/10.1080/09593330.2018.1435730 FALCO, P. B. Estrutura da comunidade microbiana (algas e bactérias) em um sistema de lagoas de estabilização em duas escalas temporais: nictemeral e sazonal. 2005. Tese (Doutorado em Hidráulica e Saneamento) - Universidade de São Paulo, São Carlos, 2005. Rev. Ambient. Água vol. 15 n. 2, e2507 - Taubaté 2020 Variability in phytoplankton community structure and influence … 11 FASTNER, J.; ABELLA, S.; LITT, A. Combating cyanobacterial proliferation by avoiding or treating inflows with high P load-experiences from eight case studies. Aquatic Ecology, v. 50, p. 367–383, 2016. https://dx.doi.org/10.1007/s10452-015-9558-8 FLORENTINO, A. P. et al. Identification of microalgae from waste stabilization ponds and evaluation of electroflotation by alternate current for simultaneous biomass separation and cell disruption. Engenharia Sanitária e Ambiental, v. 24, n. 1, p. 177-186, 2019. GANI, M. A.; ALFASANE, M. A.; KHONDKER, M. Limnology of wastewater treatment lagoons at Pagla, Narayanganj. Bangladesh Journal Botany, v. 40, p. 35–40, 2011. https://dx.doi.org/10.3329/bjb.v40i1.7995 GRANADO, D. C. Variação nictemerais e sazonais na estrutura da comunidade fitoplanctônica num sistema de lagoas de estabilização (Novo Horizonte). 2004. Dissertação (Mestrado em Hidráulica e Saneamento) - Universidade de São Paulo, São Carlos, 2004. KOBAYASHI, Y.; HODOKI, Y.; OHBAYASHI, K. Grazing impact on the cyanobacterium Microcystis aeruginosa by the heterotrophic flagellate Collodictyon triciliatum in an experimental pond. Limnology, v. 14, p. 43–49, 2013. https://dx.doi.org/10.1007/s10201-012-0384-6 KOMÁREK, J.; ANAGNOSTIDIS, K. Cyanoprokaryota 2. Teil: Oscillatoriales. In: BÜDEL, B.; KRIENITZ, L.; GÄRTNER, G.; SCHAGERL, M. (eds.). Sübwasserflora von Mitteleuropa. Munique: Elsevier Spektrum Akademischer Verlag, 2005. KOMÁREK, J.; FOTT, B. Chorophyceae (Grünalgen), Ordiniung: Chlorococcales. In: HUBER-PESTALOZZI, G. (ed.). Das Phytoplankton des Süsswaser: Systematik und Biologie. Stuttgart: E. Schwiezerbat’sche Verlagsbuch – handlung, 1983. LAU, P. S.; TAM, N. F. Y.; WONG, Y. S. Effect of Algal Density on Nutrient Removal from Primary Settled Wastewater. Environmental Pollution, v. 89, n. 1, p. 59-66, 1995. https://dx.doi.org/10.1016/0269-7491(94)00044-E LOBO, E.; LEIGHTON, G. Estructuras comunitarias de las fitocenosis planctónicas de los sistemas de desembocaduras de ríos y esteros de la zona central de Chile. Revista de Biología Marina y Oceanografia, v. 22, p. 1–29, 1986. MAHAPATRA, D. M.; CHANAKYA, H. N.; RAMACHANDRA, T. V. Treatment efficacy of algae-based sewage treatment plants. Environmental Monitoring and Assessment, v. 185, p. 7145–7164, 2013. https://dx.doi.org/10.1007/s10661-013-3090-x MARTINS, N. R. Dinâmica de algas e aspectos limnológicos em um sistema de lagoas de estabilização de esgotos sanitários em Goiânia-Goiás. 2003. Dissertação (Mestrado) - Instituto de Ciências Biológicas, Univerdidade Federal de Goiás, Goiânia, 2003. NOGUEIRA, I. de S. Biodiversidade de algas planctônicas dos corpos hídricos artificiais do parque Beija-Flor, Município de Goiânia, Goiás: Cyanobacterias, Bacillariophyceae, Euglenophyceae e Chlorophyceae. 2007. Trabalho de Conclusão de Curso (Graduação) - Universidade Federal de Goiás. Goiânia, 2007. PAPPAS, J. L.; STOERMER, E. Quantitative method for determining a representative algal sample count. Journal of Phycology, v. 32, p. 693–696, 1996. https://dx.doi.org/10.1111/j.0022-3646.1996.00693.x PASTICH, E. A.; GAVAZZA, S.; CASÉ, M. C. C.; FLORENCIO, L.; KATO, M. T. Structure and dynamics of the phytoplankton community within a maturation pond in a semiarid region. Brazilian Journal of Biology, v. 76, n. 1, p. 144-153, 2016. Rev. Ambient. Água vol. 15 n. 2, e2507 - Taubaté 2020 12 Emmanuel Bezerra D'Alessandro et al. http://dx.doi.org/10.1590/1519-6984.15214 PIELOU, E. C. Shannon’s Formula as a Measure of Specific Diversity: Its Use and Misuse on JSTOR. American Naturalist, v. 100, p. 463–465, 1966. REYNOLDS, C. S. The Ecology of Phytoplankton. New York: Cambridge University Press, 2006. RIEDIGER, W.; BUENO, N. C.; SEBASTIEN, N. Y. Spatial and temporal variation of phytoplankton in subtropical stabilization ponds. Acta Limnologica Brasiliensa, v. 27, p. 441–453, 2015. https://dx.doi.org/10.1590/S2179-975X2715 SHAMMAS, N. K.; WANG, L. K.; WU, Z. Waste Stabilization Ponds and Lagoons. In: WANG, L. K.; PEREIRA, N. C.; HUNG, Y. T. (eds). Handbook of Environmental Engineering: Biological Treatment Processes. Totowa: Humana Press, 2009. p. 315–370. SHANNON, C. E. A Mathematical Theory of Communication. The Bell System Technical Journal, v. 27, p. 379–423, 1948. https://dx.doi.org/10.1002/j.1538- 7305.1948.tb01338.x SILVA, A. S.; OLIVEIRA, R. D. Manual de análises físico-químicas de águas de abastecimento e residuárias. Campina Grande: DEC/CCT/UFPG, 2001. SEN, B.; TAHIR, M.; SONMEZ, F. Relationship of Algae to Water Pollution and Waste Water Treatment. In: ELSHORBAGY, W.; CHOWDHURY, R. K. (eds.). Water Treatment. Rijeka: InTech, 2013. p. 335–354. SCHUSTER, K. F.; TREMARIN, P. I.; SOUZA-FRANCO, G. M. De. Alpha and beta diversity of phytoplankton in two subtropical eutrophic streams in southern Brazil. Acta Botanica Brasilica, v. 29, p. 597–607, 2015. https://dx.doi.org/10.1590/0102-33062015abb0060 SIEBURTH, J.; SMETACEK, V.; LENZ, J. Pelagic ecosystem structure: Heterotrophic compartments of the plankton and their relationship to plankton size fractions. Limnology Oceanography, v. 23, p. 1256–1263, 1978. https://dx.doi.org/10.4319/lo.1978.23.6.1256 SOLDATELLI, V. F.; SCHWARZBOLD, A. Phytoplankton community in maturation lakes, Caxias do Sul, Rio Grande do Sul, Brasil. Iheringia Série Botânica, v. 65, p. 75–86, 2012. UEHLINGER, V. Étude statistique des méthodes de dénombrement planctonique. Archives des Science, v. 17, p. 121–233, 1964. https://dx.doi.org/10.1002/iroh.19650500319 UTHERMÖL, H. Zur Vervollkommnung der quantitativen Phytoplankton-Methodik. Mitteilungen Int Vereinigung Theor und Angew Limnology, v. 9, p. 1–38, 1958. VAN den HOEK, C.; MANN, D. G.; JAHNS, H. M. Algae: an introduction to phycology. Cambridge: University Press, 2008. VON SPERLING, M. Lagoas de Estabilização: Princípios do Tratamento Biológico de Águas Resíduárias. 2. ed. Belo Horizonte: UFMG, 2002. 196 p. WHITTAKER, R. H. Evolution and Measurement of Species Diversity. Taxon, v. 21, p. 213– 251, 1972. https://dx.doi.org/10.2307/1218190 ZIMBA, P. V.; HUANGA, I-S.; GUTIERREZ, D. Euglenophycin is produced in at least six species of euglenoid algae and six of seven strains of Euglena sanguinea. Harmful Algae, Rev. Ambient. Água vol. 15 n. 2, e2507 - Taubaté 2020 Variability in phytoplankton community structure and influence … 13 v. 63, p. 79–84, 2017. https://dx.doi.org/10.1016/J.HAL.2017.01.010 ZORZAL-ALMEIDA, S.; BINI, L. M.; BICUDO, D. C. Beta diversity of diatoms is driven by environmental heterogeneity, spatial extent and productivity. Hydrobiologia, v. 800, p. 7–16, 2017. https://dx.doi.org/10.1007/s10750-017-3117-3 Rev. Ambient. Água vol. 15 n. 2, e2507 - Taubaté 2020 Ambiente & Água - An Interdisciplinary Journal of Applied Science ISSN 1980-993X – doi:10.4136/1980-993X www.ambi-agua.net E-mail: [email protected] Modeling of the potential distribution of Eichhornia crassipes on a global scale: risks and threats to water ecosystems ARTICLES doi:10.4136/ambi-agua.2421 Received: 08 Jun. 2019; Accepted: 06 Feb. 2020 Pedro Fialho Cordeiro1* ; Fernando Figueiredo Goulart2 ; Diego Rodrigues Macedo3 ; Mônica de Cássia Souza Campos4 ; Samuel Rodrigues Castro5 1Departamento de Cartografia. Instituto de Geociências. Universidade Federal de Minas Gerais (UFMG), Avenida Presidente Antônio Carlos, n° 6627, CEP: 31270-901, Belo Horizonte, MG, Brazil 2Centro de Desenvolvimento Sustentável. Universidade de Brasília (UnB), Campus Universitário Darcy Ribeiro, Gleba A, CEP: 70.904-970, Asa Norte, Brasília, DF, Brazil. E-mail: [email protected] 3Departamento de Geografia. Instituto de Geociências. Universidade Federal de Minas Gerais (UFMG), Avenida Presidente Antônio Carlos, n° 6627, CEP: 31270-901, Belo Horizonte, MG, Brazil. E-mail: [email protected] 4Instituto SENAI de Tecnologia em Meio Ambiente. Serviço Nacional de Aprendizagem Industrial (SENAI), Avenida José Cândido da Silveira, n° 2000, CEP: 31035-536, Belo Horizonte, MG, Brazil. E-mail: [email protected] 5Departamento de Engenharia Sanitária e Ambiental. Faculdade de Engenharia. Universidade Federal de Juiz de Fora (UFJF), Rua José Lourenço Kelmer, s/n, CEP: 36036-900, Juiz de Fora, MG, Brazil. E-mail: [email protected] *Corresponding author. E-mail: [email protected] ABSTRACT The water hyacinth (Eichhornia crassipes) is listed among the 100 worst invasive plants and was ranked as the 11th worst invasive species in Europe, being a threat to aquatic biodiversity and water-provision. Predicting species distribution is the first step to understanding niche suitability, forecasting the invasion impact and building resilience against this species. In this study, we used a potential distribution model to assess the global risk of water hyacinth invasion by overlapping maps of highly suitable areas for water hyacinth occurrence and areas of biological importance and water scarcity. The MaxEnt - Maximum Entropy algorithm was used in the construction of the model and included five global bioclimatic layers and one of urbanized areas. Among the variables used, occurrence is mainly explained by urban areas, highlighting the importance of cities as a source or dispersion mechanism of the water hyacinth. Global biodiversity hotspots are predominantly situated in high suitability regions for the species. Ramsar sites and global protected areas are at a lower risk level compared to hotspots; however, future climate change and urban growth scenarios could put these areas at higher risk for invasion. Threats posed by the water hyacinth are possibly more acute in regions suffering from current or chronic drought. The results suggest that niche models that do not consider anthropic variables may be underestimating potential distribution of invasive species. Furthermore, the ecological plasticity of the water hyacinth and its close association with cities increase the concern about the impact of this species on the environment and on water security. Keywords: invasive species, species distribution modeling, water hyacinth. This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 Pedro Fialho Cordeiro et al. Modelagem de distribuição potencial da Eichhornia crassipes em escala global: riscos e ameaças para os ecossistemas aquáticos RESUMO O aguapé é listado entre as 100 piores plantas invasoras, além de ter sido classificado como a 11ª pior espécie invasora da Europa dado seu impacto na biodiversidade aquática e utilização de recursos hídricos pelas populações humanas. Prever a distribuição é o primeiro passo para entender a adequabilidade do nicho e prever o impacto da invasão pela espécie. Nesta pesquisa, um modelo de distribuição potencial do aguapé foi elaborado para avaliar o risco global de invasão, por meio da sobreposição deste modelo a áreas de biodiversidade e consumo de água. O algoritmo MaxEnt - Maximum Entropy foi utilizado na construção do modelo e incluiu cinco camadas bioclimáticas e uma de áreas urbanizadas. A camada de áreas urbanas foi a que mais contribuiu individualmente para o modelo e destacou a importância das cidades como fonte ou mecanismo de dispersão do aguapé. Os hotspots globais de biodiversidade estão predominantemente situados em regiões de alta adequabilidade para a espécie. Os sítios de Ramsar e as unidades de conservação globais estão em um nível de risco mais baixo do que os hotspots. No entanto, cenários futuros de mudanças climáticas e o crescimento urbano podem colocar essas áreas em maior risco de invasão. Ameaças provocadas pelo aguapé são possivelmente mais agudas nas regiões que sofrem com a seca crônica. Os resultados sugerem que modelos de distribuição potencial que não incluem variáveis antrópicas podem estar significativamente subestimando a distribuição potencial de espécies invasoras. Além disso, a plasticidade ecológica dessa espécie e sua associação com centros urbanos aumentam a preocupação com os impactos do aguapé na biodiversidade e sobre os recursos hídricos. Palavras-chave: aguapé, espécies invasoras, modelos de distribuição de espécies. 1. INTRODUCTION The water hyacinth (Eichhornia crassipes) is a free-floating aquatic macrophyte in the Pontederiaceae family and originates from the Brazilian Amazon (EPPO, 2008). It reproduces both vegetatively, via ramets formed from axillary buds on stolons, and sexually through seed production (EPPO, 2008). The species’ growth is related to an environment’s nutrient content, especially when the temperature ranges between 28ºC and 30ºC; however, growth sharply decreases below 10ºC or above 34ºC (EPPO, 2008). E. crassipes colonizes still or slow-moving water bodies, such as estuarine habitats, lakes, urban areas, watercourses, and wetlands. It can tolerate water level fluctuation extremes and seasonal variations in flow velocity, as well as extremes of nutrient availability, pH, temperature and toxic substances (Gopal, 1987). There is currently no consensus on how and when this species was introduced into environments outside its natural habitat, but its use for ornamentation in lakes and gardens, as well as in controlling nutrients and algal blooms in eutrophic environments certainly contributed to its spread (Kriticos and Brunel, 2016).The water hyacinth is present on all continents, except Antarctica, having invaded more than 50 tropical and subtropical countries (EPPO, 2008). Due to its high dispersal and growth capacity, the species is ranked on the 100 worst invasive species list as reported by the International Union for Conservation of Nature (IUCN) and it is in the top 20 list of the Spanish Invasive Species Specialist Group (ISSG) (Téllez et al., 2008). According to Nentwig et al. (2018), E. crassipes was ranked as the 11th worst invasive species in Europe. Environments colonized by E. crassipes have undergone significant changes in their structure and aquatic habitat diversity, including the proliferation of disease transmitters and high fish mortality due to low concentrations of dissolved oxygen in water (Lorenzi, 2000). Rev. Ambient. Água vol. 15 n. 2, e2421 - Taubaté 2020 Modeling of the potential distribution of … 3 Moreover, multiple water body uses have been impacted, especially uses that affect power generation, navigation, recreation and drinking water supply (Liu et al., 2016). This effect is more pronounced in regions that suffer from chronic drought (e.g., the Mediterranean), countries with tourism-based economies (e.g., Tunisia), and countries whose principal electricity supply comes from hydroelectric generation (e.g., Brazil; Kriticos and Brunel, 2016). In Sardinia (Italy), in 2010, the invasion of E. crassipes became evident when the Mare'eFoghe River, in the Province of Oristano, was covered for 8 km over an area of 560,000 m². During this event, there was an interruption of the recreational activities that usually occur in the watercourse (Brundu et al., 2012). Countries such as Portugal, India, Sri Lanka, Bangladesh, Buma, Malaysia, Indonesia, Thailand, and the Philippines recorded negative impacts and large economic losses in rice fields of around US$ 15 million due to E. crassipes (Moreira et al., 1999). In some cases, the economic impacts are so significant that they require the use of control techniques, such as in the State of Florida, in the United States, which spent more than $43 million between 1980 and 1991 on the suppression of water hyacinths. Mullin et al. (2000) reported annual expenditures for the management of the species in the order of US $500,000 in California and 3 million in Florida. Spain spent more than 14 million euros between 2005 and 2008 to control the species in the Guadiana River Basin (Téllez et al., 2008). In Lusaka, Zambia, the E. crassipes invasion on the Kafue River led to the suspension of water treatment and the reduction of the electric power generation capacity at the Gorge Dam, for at least one week (EPPO, 2008). Hydroelectric plants in Malawi and Jinga, Uganda, on the Nile River, are also frequently affected by the turbine clogging caused by water hyacinths (Wise et al., 2007). Given that invasive species commonly produce negative impacts, predicting which regions are at risk of biological invasions is important for developing successful monitoring programs and management strategies. In this context, Species Distribution Models (SDM) are tools used to predict the potential distribution of a particular species through the relationship between species occurrence and environmental condition data sets (Elith and Leathwick, 2009). Many of the modeling studies which implement SDMs carried out and reported in the literature have focused on conserving and representing the distribution of rare and endemic species (Oliveira, 2011); biogeographic analyses (Whittaker et al., 2005); potential routes of infectious diseases (Peterson et al., 2006; Levine et al., 2007); predicting the effects of climate change on the geographical distribution of species (Peterson et al., 2002; Pearson et al., 2006; Wiens et al., 2009; Kriticos and Brunel, 2016); identifying priority areas for conservation (Ortega-Huerta and Peterson, 2004); and predicting the spread risks of invasive species (Peterson, 2003; Peterson and Robins, 2003; Campos et al., 2014; Kriticos and Brunel, 2016; Liu et al., 2016). Maps generated from such models may be useful in predicting the invasive potential of exotic species, and for assessing the invasion risk in uncolonized environments (Rödder et al., 2009). We hypothesize that anthropogenic variables, such as proximity to urban areas, and climatic variables (temperature and precipitation), are determinants of the species distribution. To date, no global analyses of the potential impact of water hyacinth on biodiversity or ecosystem services have been carried out. Thus, the present study aimed to build a potential distribution model of the water hyacinth, on a global scale, in order to assess invasion risk. Additionally, the study sought to identify areas in terms of the threat level to biodiversity, water supply, and regions under chronic drought. 2. MATERIAL AND METHODS 2.1. Occurrence data acquisition and processing The occurrence points of the species were obtained from the dataset available on the Global Biodiversity Information Facility website (GBIF - gbif.org) for the period between 1960 and Rev. Ambient. Água vol. 15 n. 2, e2421 - Taubaté 2020 4 Pedro Fialho Cordeiro et al. 2017. This online platform was chosen due to the ease of access to the occurrence records on a global scale, as highlighted in various recently reported studies (Syfert et al., 2013; Campos et al., 2014; Zeng et al., 2016; Liu et al., 2016). Because inconsistencies related to the reliability of the georeferencing and taxonomic identification of the water hyacinth have been identified, inconsistent registers were removed. 2.2. Selection of environmental layers of interest Nineteen bioclimatic layers were obtained digitally from the WorldClim project (http://worldclim.org) at a spatial resolution ~ 2.5'. In addition to these variables, a binary layer of urban areas worldwide was obtained from the Socioeconomic Data and Applications Center – SEDAC (http://sedac.ciesin.columbia.edu/data/set/grump-v1-urban-ext-polygons-rev01). This layer was considered because urban areas provide favorable conditions for the distribution of E. crassipes (Dube et al., 2018). The layers were obtained in ESRI Grid format and were converted using DIVA-GIS 7.5.0 to the ASCII format, which is compatible with the MaxEnt data entry format. ArcGIS 10.3 was used to standardize the spatial incoming data in the algorithm and to generate a Pearson correlation matrix in order to evaluate the relation between the bioclimatic variables, and thus removing the highly correlated environmental layers from the final set (r >|0.70|) (Dormann et al., 2012). 2.3. The modeling algorithm The Maximum Entropy – MaxEnt v. 3.3.3 algorithm was selected to elaborate on the potential distribution model (Phillips et al., 2006). This software estimates the probability of occurrence of certain phenomena even when considering incomplete information and demonstrates excellent performance for models that only consider presence/occurrence data (Hernandez et al., 2006; Pearson et al., 2007; Wisz et al., 2008). The modeling parameters were set by default (regularization multiplier: 1; max number of background points: 10,000; replicates: 1; replicated run type: cross-validate; maximum iterations: 500; convergence threshold: 0.00001; adjust sample radius: 0). The obtained model used the best predictor variables, with 75% of the occurrence data for training and 25% for test. The environmental suitability map resulting from the model was categorized into five levels defined by the natural- breaks function in ArcGIS 10.3. The same software was also used to represent the graphical outputs of MaxEnt. 2.4. Model Evaluation and Validation In order to statistically evaluate the MaxEnt performance, analyses carried out by the software were evaluated using the Jack-Knife and the Area Under the Curve (AUC) tests. The former was carried out to evaluate the importance of the environmental layers in the explanation of the species distribution, and the latter is a statistical measure that assesses the agreement between the presence records and species distribution. An AUC value equal to 0.5 indicates that the model performance is possibly by chance similar to chance, while values closer to 1.0 indicate better model performance (Phillips et al., 2006). True Skill Statistic (TSS) was another performance measure used to evaluate the model. With values ranging from -1 to +1, positive values closer to +1 are related to the best model performance. TSS was calculated from a confusion matrix composed of hits and misses related to the prediction of the model (Allouche et al. 2006; Tables 1 and 2). Subsamples of 700 and 1000 records were used in order to verify if the n sample size used (presence records) had a significant influence on the algorithm’s performance. Moreover, an independent dataset of species occurrence (25% of the total records) was used for the model validation. For this process, a threshold was adopted based on Fixed Cumulative Value 5, aiming to binarize the environmental suitability map for invasion susceptibility in a presence- Rev. Ambient. Água vol. 15 n. 2, e2421 - Taubaté 2020 Modeling of the potential distribution of … 5 absence map of the species in order to compare the outputs of the model against actual distribution data (Phillips and Dudik, 2008). Table 1. Confusion Matrix elaborated from the hits and misses of the model. Presence Absence Predicted presence A (true positive) B (false positive) Predicted Absence C (false negative) D (true negative) A) true positive: the model predicts the species presence and the test data confirm this statement; B) false positive: the model predicts the species presence but the test data indicate absence; C) false negative: the model predicts the species absence but the test data indicate presence; and D) true negative: the model predicts the species absence and the test data confirm this statement Source: (Pearson et al., 2007). Table 2. Model performance measures resulting from the confusion matrix. Measure Formula 퐴 + 퐷 Accuracy 푁 퐴 Sensitivity (퐴 + 퐶) 퐷 Specificity (퐵 + 퐷) True Skill Statistics (TSS) (sensitivity + specificity) - 1 N: number of cases. 2.5. Environmental impacts on areas of interest Eight environmental layers in ESRI shapefile (.shp) format were considered in the potential environmental impacts assessment on a global scale, such as countries (http://www.gadm.org/); drainage networks (http://www.hydrosheds.org/ download); lentic environments - ponds, lakes and dams (https://www.worldwildlife.org/ publications/); protected areas (https://www.protectedplanet.net/c/); Ramsar Sites (https://rsis.ramsar.org/); Biodiversity Hotspots (http://www.cepf.net/resources/hotspots/Pages/default.aspx); Freshwater Ecoregions of the World (http://www.feow.org/) and drylands (http://www2.unccd.int/dryland- champions). These environmental layers were overlapped with the potential distribution model and categorized according to the environmental suitability by raster zonal statistical procedure. ArcGIS 10.3 and DIVA-GIS 7.5.0 were used in the treatment of the considered environmental layers. 3. RESULTS After excluding species occurrence points lacking geographic coordinates and location description or identified as duplicates, a total of 1316 occurrence points were selected to develop the model. From the records in this dataset, 62% of the points are located between the tropics (23° N and 23° S), while 25% are above the Tropic of Cancer and 13% are below the Tropic of Capricorn. Thus, occurrence points are distributed across all continents, except Antarctica. Although E. crassipes is native to South America, only 22% of the occurrence Rev. Ambient. Água vol. 15 n. 2, e2421 - Taubaté 2020 6 Pedro Fialho Cordeiro et al. records were on that continent, while North America accounted for about 48%, Oceania with 7.7% of the records, followed by Africa (6.1%), Europe (5.9%) and Asia (5.8%). The Pearson correlation analysis indicated a high number of correlated variables from the 19 bioclimatic layers dataset used in the model development. Six variables had no significant correlations among them (r<|0.70|) and thus they were selected for analysis (Dormann et al., 2012), five being bioclimatic and one being the binary layer of urban areas around the world, which was not tested with the other variables as its data has no correlation with the other layers (Table 3). Table 3. Selected variables and Jack-Knife test result. Code Variable Percent Contribution Permutation importance bio4 Temperature Seasonality 25.2 30.9 bio9 Mean Temperature of Driest Quarter 20.7 31.5 bio13 Precipitation of Wettest Month 18.2 13.1 bio14 Precipitation of Driest Month 8.1 12.6 bio15 Precipitation Seasonality (CV*) 1.3 1.9 urb_ext Urban extent 26.5 10 * Coefficient of Variation. According to the Jack-Knife test, "urban extent" and "temperature seasonality" variables individually contributed the most to the model. The developed model used 987 training points and 329 test points, performing better than expected at random model (AUC = 0.917 and TSS = 0.70). The result of the sensitivity statistical measure was higher than the specificity, indicating that the model produced few errors of omission (Syfert et al., 2013; Table 4). Additional tests were performed using 1000 and 700 records to evaluate the efficiency of the model when using subsamples, which verified that the reduction of the n sample size causes few changes in the model performance with hit rates higher than 93% in all cases. Table 4. Model performance measures. Number of samples 1316 1000 700 Threshold* 0.145 0.118 0.122 AUC 0.917 0.926 0.936 TSS 0.70 0.69 0.67 Overall accuracy 0.743 0.746 0.778 Sensitivity 0.963 0.946 0.892 Specificity 0.738 0.743 0.777 Hit rate (%) 96.35 95.60 93.14 *Fixed cumulative value 5. The modeled distribution is consistent with the actual points of species occurrence used in this study, as well as administrative regions in which the water hyacinth has established populations, either in their native or non-native habitats (Figure 1). The model indicated a broad spectrum of potential environments that could be invaded by the E. crassipes and then the binarized distribution model transformed the results of the environmental suitability map into a presence/absence map (Figure 2). According to the results, E. crassipes could be affecting the storage and freshwater supply in Central America, the Southeastern United States, Africa (Sub-Saharan Africa), Southern Europe, Southern and Southeastern Asia, and Oceania (note that more field data is required for confirmation). It should be highlighted that more than 33% of the main watercourses and 10% Rev. Ambient. Água vol. 15 n. 2, e2421 - Taubaté 2020 Modeling of the potential distribution of … 7 of the entire area of the world's lentic environments occur in regions that are suitable for the species occurrence. Approximately 44% of the world's lentic environments present conditions for colonization. For many tropical countries located in identified risk areas, almost all of their important watercourses are located in regions of high suitability (supplementary material – Table A: http://doi.org/10.5281/zenodo.3708474). Figure 1. Modeled potential distribution of E. crassipes on a global scale by countries. Figure 2. Presence/absence map of E. crassipes on a global scale. Many global ecoregions are under threat since more than 43% of global river basins present ideal conditions for invasion risk. There are many basins located in both North and South America with a high degree of fish species endemism that also offers the highest suitability for invasion (see http://www.feow.org) (supplementary material – Table B: http://doi.org/10.5281/zenodo.3708474). (Figure 3). About 52% of the Protected Areas (PA) of the world are under potential conditions for the establishment of E. Crassipes. Less than 1% of PAs are located in optimum conditions, corresponding to more than 279,551 km² of areas that can be or are already invaded. On the other hand, approximately 48% of the total land area of PAs lies outside of regions that offer water hyacinth suitability (Table 5). These PAs are predominantly either above the Tropic of Cancer or below the Tropic of Capricorn. Some of them are among the largest PAs on the planet, such as the Greenland biosphere reserve and the Chinese natural reserves of Sanjiangyuan and Qiangtang. Rev. Ambient. Água vol. 15 n. 2, e2421 - Taubaté 2020 8 Pedro Fialho Cordeiro et al. Figure 3. Modeled potential distribution of E. crassipes on a global scale by world freshwater ecoregions. Approximately 28% of the world's biodiversity hotspot areas are located in regions of high suitability, while 6% are in optimal conditions for the occurrence of the water hyacinth. When considering the threshold adopted in the model, 79% of the global biodiversity hotspot areas can be invaded. There are large areas of potentially threatened hotspots in Mexico, the Southeastern United States, Brazil, Madagascar, and tropical Asia (Figure 4). About 50% of Ramsar sites are in places that offer minimum conditions of suitability for the occurrence of the water hyacinth. Approximately 3% of the area of the sites or 67.6 thousand km² occur in optimal conditions and 18% are in places of high suitability (Table 5). The projected distribution indicates a high likelihood of species expansion including newly established Ramsar sites. Table 5. Quantitative results of environmental suitability in PAs, biodiversity hotspots and global Ramsar sites. Protected Areas Biodiversity Hotspots Ramsar Sites Area Area Area Class Values Area Area Area (Sq. Km) (Sq. Km) (Sq. Km) 1 0 - 0.07 (Unsuitable) 9,512,898 48% 6,818,674.62 21% 1,104,518.51 50% 2 0.071 - 0.208 (Light) 3,811,932 19% 6,480,462.70 20% 315,576.72 14% 3 0.209 - 0.352 (Moderate) 3,677,078 18% 7,788,311.41 25% 338,117.91 15% 4 0.353 - 0.525 (Potential) 2,698,951 14% 8,692,197.84 28% 405,741.49 18% 5 0.526 - 0.894 (Optimal) 279,551 1% 1,984,467.17 6% 67,623.58 3% Total 19,980,411 100% 31,764,113.75 100% 2,231,578.21 100% Approximately 30% of the world’s drylands are under potential risk of colonization, such as the in the Southwestern United States, Central-East and Southern Africa, Northern Asia, Northeastern Brazil, and Australia. Almost 50% of the available water resources in dry and sub- humid lands are potentially threatened (Figure 5 and Table 6). Rev. Ambient. Água vol. 15 n. 2, e2421 - Taubaté 2020 Modeling of the potential distribution of … 9 Figure 4. Environmental suitability of E. crassipes by (A) Biodiversity Hotspots, (B) Ramsar sites and (C) Protected Areas. Rev. Ambient. Água vol. 15 n. 2, e2421 - Taubaté 2020 10 Pedro Fialho Cordeiro et al. Figure 5. United Nations Convention to Combat Desertification (UNCC) and Convention on Biological Diversity (CBD) drylands. Table 6. Quantitative results of environmental suitability in drylands. Drylands Area (Sq. Km) Min Max Range Mean STD Sum Rate Semiarid 22,649,806 0.0000 0.8788 0.8788 0.1127 0.1415 166,897.85 0.0074 Dry sub humid 13,060,855 0.0000 0.8732 0.8732 0.1627 0.1802 138,955.59 0.0106 Additional areas included in 10,778,305 0.0000 0.8705 0.8705 0.1982 0.1730 139,715.69 0.0130 CBD definition Arid / Hyperarid 15,669,497 0.0000 0.8514 0.8514 0.0383 0.0777 39,220.17 0.0025 Min: lower suitability value; Max: highest suitability value; Range: difference between the lowest and the highest value; Mean: average suitability value; STD: standard deviation; Sum: sum of the values of the pixels of suitability; Rate: sum of the pixel values divided by the area. 4. DISCUSSION We confirmed the hypothesis that both climatic and anthropic layers are important predictors for water hyacinth distribution. Our analyses showed that the distribution of E. crassipes is limited by low temperatures at high altitudes and latitudes, as well as by heat and aridity in desert regions in Africa, Australia, Chile, Argentina, and Asia. In contrast to the Northern Hemisphere, the Southern Hemisphere has few areas that are cold enough to prevent species establishment. There is little opportunity for E. crassipes to expand the boundaries of its occupation beyond the habitats already colonized in the southern hemisphere, given that the Andes Cordillera in South America and the desert lands of Australia constitute a stress gradient due to the cold and arid conditions, respectively. We also found significant overlap amongst highly suitable regions for species occurrence and areas of water scarcity and biologically important regions. World Protected Areas (PAs) are less threatened than Ramsar sites and Biodiversity Hotspots, considering water hyacinth suitability. The results obtained for the PAs were significantly influenced by the large number of PAs located in Asia and at high latitudes, which are not suitable for the species. The Ramsar sites are in an intermediate invasion potential condition. Despite this, the projected distribution indicates a high probability of expansion of the species to newly established Ramsar sites, such as the Marais de Sacy, in France; Lake Massaciuccoli, in the region of Tuscany, Italy; and the environmental protection area of Cananéia-Iguapé-Peruíbe, in São Paulo, Brazil. Global biodiversity hotspots showed alarming results. Approximately 79% of their areas are within suitable conditions for the occurrence of the water hyacinth since the most biodiverse regions of the world are concentrated in the tropics, the portion of the planet where the water hyacinth is predominant. Rev. Ambient. Água vol. 15 n. 2, e2421 - Taubaté 2020 Modeling of the potential distribution of … 11 Threats posed by this species are possibly more acute in regions suffering from chronic drought or drought. In countries such as Greece, Albania, Macedonia, Bosnia, and Croatia, which have an extremely dry summer period and where available water resources are essential for human survival. Thus, in these locations, the environmental and economic impacts can be much more serious. Threshold selection (fixed cumulative value 5) aimed to reduce the percentage of omission errors, because the modeled species is a generalist, being able to find adequate conditions for its survival throughout the projected area of occupation (Norris, 2014). The tests performed with this threshold, with subsamples of 1000 and 700 registers, showed that the reduction of the sample size implies a small reduction in the performance of the model. In all cases, the accuracy was higher than 93%. Despite this, there was a small reduction in accuracy from 96% to 93%, due to the decrease in the independent set of data used in the validation (Zhang et al., 2015). The model presented good performance, obtaining an AUC of 0.917. However, in some cases, the use of this statistical measure is criticized (Allouche et al., 2006). In addition, the True Skill Statistics (TSS = 0.70) was calculated, which confirmed the good AUC result. Urban areas had a major influence on the projected distribution of the water hyacinth, which based on our analysis was the most influential factor explaining water hyacinth occurrence. This highlights the importance of cities serving as the source locations of hyacinth propagules due to the high levels of water pollution that contribute to species colonization. Moreover, cities serve as global dispersion vectors as they facilitate the spread of the water hyacinth far beyond its original distribution range. Due to the close association between the species and urban areas, coupled with its wide niche suitability, from the conservation and management point of view increases concern about the current and future impacts of the water hyacinth. Results obtained by Gallardo et al. (2015) corroborate our findings, as their study indicates the importance of anthropic variables in the construction of SDMs by showing that anthropic variables explained a substantial amount (23% on average) of species distributions. Megacities, which are developing mainly in Asia, may accentuate the potential for invasion of the water hyacinth on that continent. In Europe, Rodríguez-Merino et al. (2017) showed that the best predictor of potential distribution for the majority of non-native aquatic macrophytes was the human footprint. In addition, the most vulnerable areas are located near to the sea and the high population density cities. An important part of the areas for colonization of these species coincide with territories with agricultural development increase. Our projected distribution on the European continent suggests a much wider range than that found by Kriticos and Brunel (2016), who did not include urbanized areas in their model. Moreover, our projected distribution in South Africa also suggests a larger area at invasion risk, under current climatic conditions, than the areas identified by Hoveka et al. (2016), who also did not include anthropic related variables in their model. One limitation of this study refers to the small number of occurrence records obtained from the GBIF portal for South America. This limitation could be improved using other platforms that provide more information on the distribution of the species. Nevertheless, automatically reducing occurrence numbers had little effect on models’ performance, which suggests that the number of records were sufficient to test our hypothesis and strengthen the results. Another limitation is collector’s bias, as in general, most sampled areas are those of greater economic interest or more easily accessible, such as protected areas or near cities, roads and rivers (Oliveira, 2011; Norris, 2014). The use of more records would probably improve model performance. Nevertheless, although it is possible to measure collectors’ bias, it is not possible to get rid of it, and virtually all niche models have such bias. Finally, water specific variables, which are extremely important for the water hyacinth occurrence, were not used in our SDM because no reliable data is currently available on a global scale. Rev. Ambient. Água vol. 15 n. 2, e2421 - Taubaté 2020 12 Pedro Fialho Cordeiro et al. 5. CONCLUSIONS The present study consisted of the elaboration of a potential distribution model of the water hyacinth on a global scale. Risk areas were identified in terms of threats to habitat biodiversity, water supply, and chronic drought. The results of this model are consistent with the distribution of collected occurrence records. They can also be used to predict the distribution of the target species at a broad geographic scale for areas where no samples were collected, which can serve to complement and direct costly field surveys. Thus, the most vulnerable areas can be understood, directing quick response efforts. Global biodiversity hotspots are predominantly situated in regions of high environmental suitability. Ramsar sites and global protected areas are in a more secure status, but climate change scenarios and the growth of urban areas may put them at risk of invasion. A more detailed and individual evaluation for each of these areas is suggested in order to categorize them according to their environmental suitability for invasion susceptibility and proximity to recorded E. crassipes locations. Furthermore, we recommend that SDMs should use anthropogenic layers to better represent species distribution. From the methodological point of view, this work adds to the literature as it brings evidence that modeling invasive species niches needs to include anthropic layers as explanatory variables, otherwise potential distribution may be underestimated. In this case, more than one quarter of the hyacinth occurrence is explained by the presence of urban centers, greatly expanding the range of areas identified as highly suitable when compared to previous studies that only relied on bioclimatic conditions to model the occurrence of this species. From the conservation and water security point of view, we demonstrate that the water hyacinth should occur in areas around the globe where humidity and heat levels are appropriate. Given increasing rates of urbanization, particularly in tropical and developing countries (D’Amour et al., 2017), these and surrounding areas provide ideal environments for water hyacinth occurrence. Such findings increase the concern of the current and future impact of this plant on aquatic biodiversity and water resources. Finally, understanding the full invasion potential of this species is crucial for decisions that involve species management and to avoid negative impacts. The methodology used in this study could be used in evaluating the dispersion potential of other invasive species. 6. ACKNOWLEDGMENTS Diego Rodrigues Macedo was supported by CNPq (402907/2016-7), PPGs-UFMG Geografia and Análise e Modelagem de Sistemas Ambientais (Capes Finance Code 001), P&D ANELL (GT599). Fernando Figueiredo Goulart received a PNPD scholarship (Finance Code 001) from the Coordenação de Aperfeiçoamento de Pessoal de Ensino Superior-CAPES. 7. REFERENCES ALLOUCHE, O.; TSOAR, A.; KADMON, R. Assessing the accuracy of species distribution models: prevalence, kappa and the true skill statistic (TSS). Journal of Applied Ecology, v. 43, p.1223–1232, 2006. https://dx.doi.org/10.1111/j.1365-2664.2006.01214.x BRUNDU, G.; STINCA, A.; ANGIUS, L.; BONANOMI, G.; CELESTI-GRAPOW, L.; D'AURIA, G. Pistia Stratiotes L. and Eichhornia crassipes (Mart.) Solms.: emerging invasive alien hydrophytes in Campania and Sardinia (Italy). Bulletin OEPP/EPPO Bulletin, v. 42, n. 568–579, 2012. https://dx.doi.org/10.1111/epp.12004 Rev. Ambient. Água vol. 15 n. 2, e2421 - Taubaté 2020 Modeling of the potential distribution of … 13 CAMPOS, M. C. S.; ANDRADE, A. F. A.; KUNZMANN, B.; GALVÃO, D. D.; SILVA, F. A.; CARDOSO, A. V.; CARVALHO, M. D.; MOTA, H. R. Modelling of the potential distribution of Limnoperna fortunei (Dunker, 1857) on a global scale. Aquatic Invasions, v. 9, p. 253-265, 2014. http://dx.doi.org/10.3391/ai.2014.9.3.03 D’AMOUR, C. B.; REITSMA, F.; BAIOCCHI, G.; BARTHEL, S.; GÜNERALP, B.; ERB, K.; HARBEL, H.; CREUTZIG, K.; SETO, K. C. Future urban land expansion and implications for global croplands. Proceedings of the National Academy of Sciences, v. 114, n. 34, p. 8939-8944, 2017. https://doi.org/10.1073/pnas.1606036114 DORMANN, C. F.; ELITH, J.; BACHER, S.; BUCHMANN, C.; GUDRUN, C. G.; GARCÍA MARQUÉZ, J. R.; GRUBER, B.; LAFOURCADE, B.; LEITÃO, P. J.; MÜNKEMÜLLER, T.; MCCLEAN, C.; OSBORNE, P. E.; BJÖRN, R.; SCHRÖDER, B.; SKIDMORE, A. K.; ZURELL, D.; LAUTENBACH, S. Collinearity: a review of methods to deal with it and a simulation study evaluating their performance. Ecography, v. 35, p. 001–020, 2012. https://doi.org/10.1111/j.1600-0587.2012.07348.x DUBE, T.; SIBANDA, M.; BANGAMWABO, V.; SHOKO, C. Establishing the link between urban land cover change and the proliferation of aquatic hyacinth (Eichhornia crassipes) in Harare Metropolitan, Zimbabwe. Physics and Chemistry of the Earth, v. 108, p. 19– 27, 2018. https://doi.org/10.1016/j.pce.2018.09.010 ELITH, J.; LEATHWICK, J. R. Species distribution models: ecological explanation and prediction across space and time. Annual Review of Ecology, Evolution and Systematics, v. 40, p. 677–697, 2009. https://doi.org/10.1146/annurev.ecolsys.110308.120159 EPPO. Eichhorniacrassipes. Bulletin OEPP/EPPO Bulletin, v. 38, p. 441–449, 2008. GALLARDO, B.; ZIERITZ, A.; ALDRIDGE, D. C. The importance of the human footprint in shaping the global distribution of terrestrial, freshwater and marine invaders. PLOS One, v. 10, n. 8, p. 1-17, 2015. https://doi.org/10.1371/journal.pone.0125801 GOPAL, B. Water Hyacinth. Amsterdam: Elsevier, 1987. HERNANDEZ, P. A.; GRAHAM, C. H.; LAWRANCE, L.; MASTER, A. N. D.; DEBORAH, L. A. The effect of sample size and species characteristics on performance of different species distribution modeling methods. Ecography, v. 29, p. 773-785, 2006. https://doi.org/10.1111/j.0906-7590.2006.04700.x HOVEKA, L. N.; BEZENG, B. S.; YESSOUFOU, J. S.; VAN DER BANK, M. Effects of climate change on the future distributions of the top five freshwater invasive plants in South Africa. South African Journal of Botany, p. 33-38, 2016. https://doi.org/10.1016/j.sajb.2015.07.017 KRITICOS, D. J.; BRUNEL, S. Assessing and managing the current and future pest risk from water hyacinth (Eichhornia crassipes), an invasive aquatic plant threatening the environment and water security. PLOS One, v. 11, n. 8, p. 1-18, 2016. https://doi.org/10.1371/journal.pone.0120054 LEVINE, R. S.; PETERSON, A. T.; YORITA, K. L.; CARROLL, D.; DAMON, I. K.; REYNOLDS, M. G. Ecological niche and geographic distribution of human monkeypox in Africa. Plos One, v. 2, p. 1-7, 2007. https://doi.org/10.1371/journal.pone.0000176 LIU, D.; WANG, R.; GORDON, D. R.; SUN, X.; CHEN, L.; WANG, Y. Predicting plant invasions following china’s water diversion project. Environmental Science & Technology, v. 51, n. 3, p. 1450-1457, 2016. https://doi.org/10.1021/acs.est.6b05577 Rev. Ambient. Água vol. 15 n. 2, e2421 - Taubaté 2020 14 Pedro Fialho Cordeiro et al. LORENZI, H. Plantas Daninhas do Brasil: terrestres, aquáticas, parasitas e tóxicas. 3. ed. Nova Odessa: Instituto Plantarum, 2000. MOREIRA, I.; FERREIRA, T.; MONTEIRO, A.; CATARINA, L.; VASCONCELOS, T. Aquatic weeds and their management in Portugal: insights and the international context. Hydrobiologia, v. 415, p. 229–234, 1999. https://doi.org/10.1007/978-94-017-0922- 4_32 MULLIN, B. H.; ANDERSON, L. W. J.; DITOMASO, J. M.; EPLEE, R. E.; GETSINGER, K. D. Invasive plant species. Council for Agricultural Science and Technology, n. 13, 2000. NENTWIG, W.; BACHER, S.; KUMSCHICK, S.; PYŠEK, P.; VILÀ, M. More than “100 worst” alien species in Europe. Biological Invasions, v. 20, n. 6, p. 1611-1621, 2018. https://doi.org/10.1007/s10530-017-1651-6 NORRIS, D. Model thresholds are more important than presence location type: understanding the distribution of lowland tapir (Tapirusterrestris) in a continuous Atlantic forest of southeast Brazil. Tropical Conservation Science, v. 7, n. 3, p. 529-547, 2014. https://doi.org/10.1177/194008291400700311 OLIVEIRA, U. Diversidade e Biogeografia de Aranhas do Brasil: Esforço Amostral, Riqueza Potencial e Áreas de Endemismo. 2011. 103 f. Tese (Doutorado) - Universidade Federal de Minas Gerais, Belo Horizonte, 2011. ORTEGA-HUERTA, M. A.; PETERSON, A. T. Modelling spatial patterns of biodiversity for conservation prioritization in North-eastern Mexico. Diversity and Distributions, v. 10, p. 39-54, 2004. https://doi.org/10.1111/j.1472-4642.2004.00051.x PEARSON, R. G. C.; THUILLER, W.; ARAÚJO, M. B.; MARTINEZMEYER, E.; BROTONS, L.; MCCLEAN, C. MILES, L.; SEGURADO, P.; DAWSON, T. C.; LEES, D. C. Model based uncertainty in species range prediction. Journal of Biogeography, v. 33, p. 1704- 1711, 2006. https://doi.org/10.1111/j.1365-2699.2006.01460.x PEARSON, R. G. C.; RAXWORTHY, J.; NAKAMURA, M.; PETERSON, A. T. Predicting species distributions from small numbers of occurrence records: a test case using cryptic geckos in Madagascar. Journal of Biogeography, v. 34, p. 102-117, 2007. https://doi.org/10.1111/j.1365-2699.2006.01594.x PETERSON, A. T. Predicting the geography of species’ invasions via ecological niche modeling. The Quarterly Review of Biology, v. 78, p. 419–433, 2003. https://doi.org/10.1086/378926 PETERSON, A. T.; ROBINS, C. R. Using ecological niche modeling to predict Barred Owl invasions with implications for Spotted Owl conservation. Conservation Biology, v. 17, p. 1161-1165, 2003. https://doi.org/10.1046/j.1523-1739.2003.02206.x PETERSON, A. T.; LASH, R. R.; CARROLL, D. S.; JOHNSON, K. M. Geographic potential for outbreaks of Marburg hemorrhagic fever. American Journal of Tropical Medicine and Hygiene, v. 75, p. 9-15, 2006. https://doi.org/10.4269/ajtmh.2006.75.1.0750009 PETERSON, A. T.; ORTEGA-HUERTA, M. A.; BARTLEY, J.; SÁNCHEZ-CORDERO, V.; SOBERÓN, J.; BUDDEMEIER, R. H.; STOCKWELL, D. R. B. Future projections for Mexican faunas under global climate change scenarios. Nature, v. 416, p. 626-629, 2002. https://doi.org/10.1038/416626a Rev. Ambient. Água vol. 15 n. 2, e2421 - Taubaté 2020 Modeling of the potential distribution of … 15 PHILLIPS, S. J. R. P.; ANDERSON, R.; SCHAPIRE, E. Maximum entropy modeling of species geographic distributions. Ecological Modelling, v. 190, p. 231-259, 2006. https://doi.org/10.1016/j.ecolmodel.2005.03.026 PHILLIPS, S. J.; DUDIK, M. Modelling of species distributions with MaxEnt: new extensions and a comprehensive evaluation. Ecography, v. 31, p. 161-175, 2008. https://doi.org/10.1016/j.ecolmodel.2005.03.026 RÖDDER, D.; SCHMIDTLEIN, S.; VEITH, M.; LOTTERS, S. Alien Invasive Slider Turtle in Unpredicted Habitat: A Matter of Niche Shift or of Predictors Studied? PlosOne, v. 4, n. 11, p. 1–9, 2009. https://doi.org/10.1371/journal.pone.0007843 RODRÍGUEZ-MERINO, A.; FERNÁNDEZ-ZAMUDIO, R.; GARCÍA-MURILLO, P. An invasion risk map for non-native aquatic macrophytes of the Iberian Peninsula. Anales Del Jardín Botánico de Madrid, v. 74, n. 1, p. 1–10, 2017. https://doi.org/10.3989/ajbm.2452 SYFERT, M. M.; SMITH, M. J.; COOMES, D. A. The effects of sampling bias and model complexity on the predictive performance of Maxent species distribution models. PLoS ONE, v. 8, n. 2, p. e55158, 2013. https://doi.org/10.1371/journal.pone.0055158 TÉLLEZ, T. R.; LÓPEZ, E.; GRANADO, G. L.; PÉREZ, E. A.; LÓPEZ, R. M.; GUZMÁN, J. M. S. The Water hyacinth, Eichhornia crassipes: an invasive plant in the Guadiana River Basin (Spain). Aquatic Invasions, v. 3, p. 42–53, 2008. https://doi.org/10.3391/ai.2008.3.1.8 WIENS, J. A.; STRALBERG, D.; JONGSOMJIT, D.; HOWELL, C. A.; SNYDER, M. A. Niches, models, and climate change: assessing the assumptions and uncertainties. Proceedings of the National Academy of Sciences of the United States of America, v. 106, p. 19729-19736. 2009. https://doi.org/10.1073/pnas.0901639106 WISE, R. M.; WILGEN, B. W.; HILL, M. P.; SCHULTHESS, F.; TWEDDLE, D.; CHABI- OLAY, A. The economic impact and appropriate management of selected invasive alien species on the African continent. Global Invasive species Programme. CSIR Report No. CSIR/NRE/RBSD/ER/2007/0044/C. Feb. 2007. Available at: http://www.issg.org/pdf/publications/GISP/Resources/CSIRAISmanagement.pdf. Access: Feb. 2020. WISZ, M. S.; HIJMANS, R. J.; LI, J.; PETERSON, A.T.; GRAHAM, C. H.; GUISAN, A. E. Predicting species distributions working group. Effects of sample size on the performance of species distribution models. Diversity and Distributions, v. 14, p. 763-773, 2008. https://doi.org/10.1111/j.1472-4642.2008.00482.x WHITTAKER, R. J.; ARAUJO, M. B.; PAUL, J.; LADLE, R. J.; WATSON, J. E. M; WILLIS, K. J. Conservation biogeography: assessment and prospect. Diversity and Distributions, v. 11, p. 3–23, 2005. https://doi.org/10.1111/j.1366-9516.2005.00143.x ZENG, Y.; LOW, B. W.; DARREN, C., J., Y. Novel methods to select environmental variables in MaxEnt: A case study using invasive crayfish. Ecological Modelling, p. 5-13, 2016. https://doi.org/10.1016/j.ecolmodel.2016.09.019 ZHANG, L.; LIU, S.; SUN, P.; WANG, T.; WANG, G.; ZHANG, X. Consensus forecasting of species distributions: the effects of niche model performance and niche properties. PLoS ONE, v. 10, n. 3, p. e0120056, 2015. https://doi.org/10.1371/journal.pone.0120056 Rev. Ambient. Água vol. 15 n. 2, e2421 - Taubaté 2020