Distribution of Heavy Metals (Cd, Cu, Co, Cr, Hg, Mn, Ni, Pb, Zn, and As) in Overbank Sediments of Ibar Tributaries (in Serbia) Božidar V. Đokić ( [email protected] ) Geological Survey of Serbia https://orcid.org/0000-0002-0162-7433 Dragana Vidojević Serbian Environmental Protection Agency Olivera Đokić Highway Institute https://orcid.org/0000-0002-8464-3673 Research Article Keywords: overbank sediments, geological and pedological composition, factor analysis, Spearman’s rank correlation Posted Date: August 25th, 2021 DOI: https://doi.org/10.21203/rs.3.rs-821344/v1 License: This work is licensed under a Creative Commons Attribution 4.0 International License. Read Full License Page 1/21 Abstract The Ibar River is an international river whose watercourse passes next to numerous technogenic landlls and chemical-industrial complexes. They can affect the quality of water in the river, as well as the quality of overbank sediments. The river ows into the West Morava River near Kraljevo and it represents its largest tributary. The analysis of the overbank sediments of Ibar tributaries showed high concentration of heavy metals at some points. The statistical analysis of the content determined the existence of two synthetic factors around which heavy metals were concentrated. The comparison of the chemical composition of overbank sediment with the composition of geological and pedological substratum on which they were developed showed that the increased concentrations of heavy metals were mostly a product of geological and pedological composition of the river’s substratum and basin, and had no connection with (possible) anthropogenic factors. However, due to the sensitivity and proximity of potential pollutants, the necessity to constantly monitor chemical composition of overbank sediments in the river basin was determined. Introduction The Ibar River is an international river. Its river source is located on the Hajla Mountain in Montenegro at an altitude of 2,400 m. It ows through Montenegro and Serbia. In central Serbia, near Kraljevo, it ows into the West Morava River as its largest tributary. The upper, middle, and lower course can be differentiated. The upper course is located mostly in Montenegro and only partly in Serbia (Kosovo and Metohija). The middle and lower course of the river were investigated in this paper. The river often ows through narrow and not easily accessible gorges. A 110 m high dam was built 24 km upstream from Kosovska Mitrovica on the Ibar, and because of this, the articial lake Gazivode was created. The total length of Ibar is 276 km, and the river’s basin surface area is 8,059 km2 (Fig. 1). Larger tributaries in Serbia are Sitnica River, Rudnjačka River, Raška River, Brvenica River, Jošanica River, Studenica River, and Ribnica River. The Ibar River ows through areas with specic geomorphological structure. The inow of wastewater, which originates from mining-industrial complexes, tailings, intensive agriculture, illegal landll sites, etc., into the river basin is high. Due to orography, the river often overows. Numerous studies indicate that more than 12% of watercourses that belong to the Ibar River basin are susceptible to ooding (Dragićević et al. 2019). When the water that ooded the area retreats, it leaves pollutants behind. Numerous studies have conrmed this. There are few studies that investigate the direct origin and chemical composition of this material. The middle course of Ibar has a high inow of industrial wastewater that originates from the wider area of Kosovska Mitrovica, Zvečan, and Leposavić. Waters from the wider area of Kosovska Mitrovica come from several mining-metallurgical-chemical plants and landlls of Trepča Mines. The watercourse passes by the Pb-Zn ore otation tailings site in Leposavić and further downstream next to the otation and otation tailings of Suva Ruda (Rudnica and Kukanjica streams). The contouring showed that the Page 2/21 Rudnica tailings covered the area of 18 hectares 79 acres 8 m2. The granulometric composition of the tailings content showed that it consisted of siltstone / sand. The content of chalcopyrite was three times higher than content of andradite in one part of the tailings site, while other minerals were less present. In other part of the site quartz and gypsum were equally present, and in the third part of the site quartz was predominant. The distribution of heavy metals in the tailings site did not exhibit any patterns. One part of the site had elevated U content compared to the natural background radiation. Kukanjica Stream tailings covers the area of 10 hectares 48 acres 9 m2. The granulometric composition showed the presence of clay/ siltstone. The X-ray analysis determined that quartz was predominant compared to clay, siderite, pyrite, gypsum, and ankerite, and feldspars and calcite occurred locally. Hydro-chemical analysis showed increased contents of Pb, Zn, and Fe compared to standards for class II water, while the concentrations of As and Sb were above the allowed for class IV waters. The soil samples from the area surrounding the tailings site contained the concentrations of Zn and As in the phytotoxic range, and Co, Cr, Sb, Sn, Cu, and Cd had increased content locally (Đokić 2011, Đokić et al. 2013). The tailings sites are located in Tadenje (Progorelica), Jarandol, Pobrdje, Piskanja, Bela Stena, and Korlaća. Wastewaters from these tailings ow directly into the Ibar. Jarandol and Progorelica tailings were created as a result of the exploitation of coal. The exploitation began at the end of the 19th century. The areas of initial exploitation and tailings were spontaneously recultivated with pioneer plants. The mean U and Th content at this site is higher compared to their mean content in the earth’s crust. The excavated coal at the Piskanje location is rened by separation process. The tailings site for boron minerals is located at Pobrdje. This site was formed after manual sorting of the excavated ore. Hydro- chemical analysis showed increased content of Fe and Pb, and increased contents of Zn, Cu, Cd, Cr, Co, Ni, Sb, As, and Hg were high as well. Bela Stena tailings site was formed after the exploitation of magnesite during the last twenty years of the 20th century. The tailings site at Korlaća was formed after the exploitation and processing of asbestos (Đokić 2011). The lower course of Ibar receives the inow of industrial and communal waters from Raška and Baljevac (Nikolić et al. 2014). Ibar is polluted by industrial wastewaters that originate from dairy and meat industries, municipal wastewater, etc. The river passes by 47 settlements in its middle and lower course which endanger the quality of the water and its sediments (Nikolić et al. 2014). All in all, the river is polluted by industrial, agricultural, and municipal wastewaters. The construction of several hydroelectric power plants is planned on the Ibar. Numerous analyses have been performed on how these hydroelectric power plants could affect the quality of water. The conclusion was that the planned accumulations would prevent the formation of the stable thermal stratication during the warmer part of the year, which would further impede the full realization of eutrophication potential (Jaćimović et al. 2014). The quality of the water in river is systematically and continuously controlled by measuring the parameters that inuence it the most, which are the concentrations of Pb, Cu, Ni, Co, Cd, Mn, Zn, Cr, and Hg. These measurements are performed at several locations along the Ibar watercourse (SEPA 2019). Page 3/21 The suspended material transported by the river during the ood, which is frequent, is deposited as the overbank sediment in the soil on the banks of the Ibar. This sediment, most of all, affects the chemical properties of the soil. However, the geological stratum on which the soil is developed has the greatest inuence on the structure and mineral and chemical composition of the soil (Dorfer et al. 2018a, Dorfer et al. 2018b). The climate also has considerable inuence on these properties (Gore 2009). The overbank sediment is a ood sediment formed under the conditions of higher energy of relief from the material transported in the suspension. The overbank sediment is a complex, dynamic system susceptible to changes. The tributaries of Ibar often have the characteristics of a torrent, which can cause the mixing of materials (overbank sediments) (Veljković et al. 2019, Peh and Miko 2001). Heavy metals found in overbank sediments can be remobilized in different ways (e.g. during new oods) and can again become a source of contamination (Adánez Sanjuán et al. 2018). These tributaries also ow through numerous settlements and receive their wastewaters. This way they directly or indirectly affect the quality of the water in Ibar and the quality of the sediment as well. The sources of the pollution can be diffuse, point, and combined, and in the case of this river, they are combined. The regularity of the increased presence of heavy metals (Cd, Cu, Co, Cr, Hg, Mn, Ni, Pb, Zn, and As) in the overbank sediments of the tributaries of Ibar was analyzed in this paper. Materials And Methods Sampling The collection of the samples was performed according to the recommendations for the drawing of the Geochemical Map of Serbia 1:500,000, stream, overbank, and oodplain sediments (Đokić 2016). The coordinates for the sampling were determined using a GARMIN-GPSmap60CSx. The depth of sample collection was from 0 to 10 cm. To avoid the inuence of organic matter, samples were collected under the layer of humus. The collection was performed by an Eijkelkamp probe with a nozzle for soil testing and a spade with a stainless steel blade. Each sample consisted of 10 subsamples which were homogenized in the eld. A total of 75 samples (750 subsamples) were collected. The samples collected for the realization of the project Geochemical Map of Serbia 1:500,000, stream, overbank, and oodplain sediments were used in this study (Đokić 2017, Đokić 2018).