Marine Pollution Bulletin 60 (2010) 2225–2232
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Marine Pollution Bulletin 60 (2010) 2225–2232 Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul Inorganic As speciation and bioavailability in estuarine sediments of Todos os Santos Bay, BA, Brazil ⇑ V. Hatje a,c, , S.M. Macedo b,c, R.M. de Jesus b,c,d, G. Cotrim a, K.S. Garcia e, A.F. de Queiroz e, S.L.C. Ferreira b,c a Laboratório de Oceanografia Química, Instituto de Química, UFBA, Campus Ondina, Salvador, BA, 40170-290, Brazil b Instituto de Química, UFBA, Campus Ondina, Salvador, BA, 40170-290, Brazil c Instituto Nacional de Ciência e Tecnologia, INCT, de Energia e Ambiente, UFBA, Salvador, BA, 40170-290, Brazil d Departamento de Ciências Exatas e Tecnológicas, Universidade Estadual de Santa Cruz, Ilhéus, BA, 45650-000, Brazil e Departamento de Geoquímica, Universidade Federal da Bahia, BA, 45650-000, Brazil article info abstract Keywords: The spatial distribution of As (total As, As (III) and As (V)) in estuarine sediments from the main tributar- Speciation ies of Todos os Santos Bay, BA, Brazil, was evaluated under high and low flow conditions. The concentra- Arsenic tions of As were determined using a slurry sampling procedure with hydride generation atomic Paraguaçu River absorption spectrometry (HG-AAS). The highest concentrations were observed at estuary mouths, and Subaé River exceeded conservative lower threshold value (Threshold Effects Level; TEL). Due to the oxic conditions Jaguaripe River and abundance of Mn and Fe (oxyhydr)oxides in the sediments, most inorganic arsenic in the Subaé Slurry sampling and Paraguaçu estuaries was present as As (V). Nevertheless, the concentration of As (III) at several loca- tions along the Jaguaripe River were also above the TEL value, suggesting that As may be toxic to biota. In the Subaé estuary, antropogenic activities are the main source of As. At the Jaguaripe and at Paraguaçu estuaries, nevertheless, natural sources of As need to be considered to explain the distribution patterns. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction pollutants, and it is a public concern due to its widespread usage in both agriculture and industry ( USEPA, 1998 ). In aquatic environments, arsenic occurs in both organic and Naturally occurring As in aquatic environments originates from inorganic forms. Inorganic forms of arsenic consist primarily of the weathering of primary and secondary minerals ( Datta et al., arsenite (As (III)) and arsenate (As (V)) compounds, while there 2007 ). Arsenic occurs as a major constituent in more than 200 min- are many organic forms of arsenic, including monomethylersonic erals. Approximately 60% of arsenic minerals are arsenates, 20% acid (MMA) and dimethylarsonic acid (DMA) ( Ko et al., 2004; Plant sulfides and sulfosalts, and the remaining 20% are arsenides, arse- et al., 2005 ). Depending on the geochemical environment (pH, re- nites, oxides, alloys and polymorphs of elemental As ( Plant et al., dox conditions, organic matter, etc.), arsenic can exist in four oxi- 2005 ). The most abundant As ore mineral is arsenopyrite, FeAsS dation states, namely, À3, 0, +3 and +5. However, environmental (Tomkins et al., 2006 ). It is generally accepted that arsenopyrite, exposure often occurs through As (III) and As (V) ( Hughes, 2002 ), together with the other dominant As–sulfide minerals realgar which are highly toxic and lead to a wide range of health problems and orpiment, are only formed under high temperature conditions in humans. As (V) sorbs more strongly to minerals than As (III); in the earth’s crust. However, authigenic arsenopyrite has been re- thus, As (V) is slightly less toxic and less mobile ( Pierce and Moore, ported in sediments by Rittle et al. (1995) . 1982 ). However, both As (III) and As (V) are carcinogenic, muta- Anthropogenic activities have progressively accelerated the genic and teratogenic ( National Research Council, 1999 ). Many transfer of arsenic from the geosphere to the surface environment cases of acute and chronic arsenic poisoning have been reported and have distributed arsenic throughout the biosphere ( Plant et al., in various parts of the world ( Gray et al., 1989; WHO, 1993; Se- 2005 ). Anthropogenic activities that alter the natural biogeochem- nesse et al., 1999; Saha, 2003 ). Arsenic is the number one toxin ical cycle of As include mining, smelting, combustion of coals, on the US Environmental Protection Agency’s list of prioritised refining of fossil-fuels, use of biocides such as wood preservatives and pesticides, waste incineration, and the manufacturing and use of feed additives. The total arsenic concentration in sediments and water depends ⇑ Corresponding author at: Laboratório de Oceanografia Química, Instituto de first on the local geology, and then on potential anthropogenic in- Química, UFBA, Campus Ondina, Salvador, BA, 40170-290, Brazil. Tel./fax: +55 71 32355166. puts. However, because the toxicity, mobility and availability of E-mail address: [email protected] (V. Hatje). arsenic rely on its chemical form, quantitative analyses and 0025-326X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi: 10.1016/j.marpolbul.2010.08.014 2226 V. Hatje et al. / Marine Pollution Bulletin 60 (2010) 2225–2232 speciation studies are necessary. To evaluate the toxicity and bio- knowledge of the distribution and speciation of arsenic will en- availability of As, samples from the region of interest are often ex- hance the understanding of As toxicity and bioavailability. tracted with water, dilute acetic acid or EDTA. It is crucial to determine the bioavailability, once it is a relative measure of the 2. Methods fraction of the total metal that an organism actually can takes up from all possible sources, including water, sediments and food 2.1. Study area (Luoma and Rainbow, 2008 ). Sequential extractions, carried out by the sequential use of reagents with different chemical proper- Todos os Santos Bay (BTS) is centred at 12 °50 0S latitude and ties, are also frequently employed to estimate bioavailability and 38 °38 0W ( Fig. 1 ) longitude, and possesses a maximum width and toxicity. The procedures developed by Tessier et al. (1979) and length of 32 km and 50 km, respectively. BTS is located in the vicin- Quevauviller et al. (1994) are the most widely used sequential ity of Salvador, the third largest metropolitan area of Brazil, and the extractions to study coastal sediments; however, a limited number home of the largest petrochemical complex in the southern hemi- of studies on the determination of As from estuarine sediments sphere. Several anthropogenic activities influence the system’s have been conducted ( Matera et al., 2003; Giacomino et al., 2010 ). environmental quality, such as the influx of domestic effluents, so- Problems associated with sample preparation, lixiviation and/or lid wastes, agriculture, industrial (chemicals, petrochemicals, decomposition are frequently encountered in the determination of smelters, etc.) and mining activities ( CRA, 2008; Hatje and de And- trace elements. Moreover, some arsenic species are volatile, and rade, 2009 ). As a result, relatively high concentrations of trace ele- acid digestions must be performed in a closed system to reduce ments and hydrocarbons (HPAs) are observed in marine losses ( Costa et al., 2009 ). Currently, solid sampling is the preferred invertebrates ( Wallner-Kersanach et al., 2000 ; CRA, 2004; Amado technique for arsenic determination in solid matrices due to the Filho et al., 2008 ; Santil, 2010; Hatje et al., 2009 ), sediments complete elimination of a sample pre-treatment step ( Vale et al., (CRA, 2004; Venturini et al., 2004; Hatje et al., 2006; Barros 2006 ). However, this technique requires specialised instrumenta- et al., 2008; Venturini et al.; 2008; Hatje et al., 2009 ), and atmo- tion that is not always available. Slurry sampling ( Cal-Pietro spheric particles ( Pereira et al., 2007; da Rocha et al., 2009 ), espe- et al., 2002; Santos and Nóbrega, 2006 ) is an excellent alternative, cially in the northern region. eliminating the need for a sample pre-treatment step and reducing The Paraguaçu, Subaé and Jaguaripe River ( Fig. 1 ) are the three the risk of analyte loss or contamination. Due to the advantages of main tributaries of the BTS. The catchment of the Paraguaçu River slurry sampling, several methods for the determination of arsenic is 56,300 km 2, and downstream of the Pedra do Cavalo Dam, Parag- À in environmental matrices have been proposed (e.g. Macedo uaçu presents an average discharge of 64 m 3 s 1 (Genz, 2006 ). et al., 2009 ). Maximum flows are observed in summer months, especially in The objective of this work was to characterize the spatial distri- December–January. The other two main catchments of the BTS bution of Total As and the inorganic As species along the three are the Jaguaripe (2200 km 2) and Subaé River (600 km 2). The max- main tributaries of Todos os Santos Bay, BA, Brazil, during the imum discharge of the Jaguaripe and Subaé River occurs in June À wet and dry season, employing slurry sampling (SS) and hydride (winter), where a mean monthly discharge of 28 m 3 s 1 and À generation atomic absorption spectrometry (HG-AAS). Improved 9 m 3 s 1 is observed, respectively ( Cirano and Lessa, 2007 ). Fig. 1. Sampling sites located along the tributaries of Todos os Santos Bay, Bahia, Brazil. V. Hatje et al. / Marine Pollution Bulletin 60 (2010) 2225–2232 2227 À 2.2. Sampling flow of argon at a rate of 100 mL min 1. Arsenic concentrations were measured by an atomic absorption spectrometer with an ar- Two campaigns were conducted at the Paraguaçu, Subaé and senic hollow cathode lamp (Varian model SpectrAA 220, Mulgrave, Jaguaripe estuaries ( Fig. 1 ) between 2003 and 2007, in which data Victoria, Australia), and atomisation was achieved in a quartz tube were collected during both the wet and dry seasons. In this study, heated with an air-acetylene flame. The absorption wavelength salinity, temperature and the concentration of dissolved oxygen was set to 193.7 nm, and measurements were made with a lamp and suspended particulate matter (SPM) were measured at each current of 10 mA and a slit width of 0.5 nm.