Dissolved arsenic in the upper Paraguay River basin and Pantanal wetlands

Author(s)

Richter, Larissa ^[1] ; Hernandez, Amauris Hechavarria ^[1] ; Pessoa, Gustavo S. ^[1] ; Zezzi Arruda, Marco Aurelio ^[1] ; Rezende-Filho, Ary T. ^[2] ; de Almeida, Rafael Bartimann ^[3] ; Menezes, Hebert A. ^[2] ; Valles, Vincent ^[4] ; Barbiero, Laurent ^{[1, 5, 6, 7]} ; Fostier, Anne Helene ^[1]

Affiliation

^[1] Univ Estadual Campinas, Chem Inst, Campinas, SP - Brazil

^[2] Fed Univ South Mato Grosso FAENG, Campo Grande, MS - Brazil

^[3] Grande Dourados Fed Univ, UFGD, Dourados, MS - Brazil

^[4] UAPV, Avignon - France

^[5] IRD, GET, Toulouse - France

^[6] Sao Carlos Fed Univ UFSCar, Sorocaba, SP - Brazil

^[7] Sao Paulo Univ CENA USP, Piracicaba, SP - Brazil

• Document type: Journal article
• Source: Science of The Total Environment; v. 687, p. 917-928, OCT 15 2019.
• Web of Science Citations: 0

Abstract

Although high levels of dissolved arsenic were detected in surface and ground waters of Nhecolandia, a subregion of the vast Pantanal wetlands in Brazil, the possible sources have not been clearly identified and the potential release from the wetland to the draining rivers has not been investigated. In this study we measured the dissolved As content in all the rivers and small streams that supply the southern Pantanal region, as well as in the two main rivers draining the wetland, i.e., the Cuiaba and Paraguay rivers and tributaries. In addition, Arsenic in surface waters, perched water-table, soils and sediments from 3 experimental sites located in the heart of Nhecolandia were compared. On the one hand, the results show the absence of As contamination in rivers that supply the Pantanal floodplain, as well as a lack of significant release from the floodplain to the main drains. The As contents in the rivers are <2 mu g L-1, with variations that depend on the lithology and on the geo-morphology at the collection point (uplands or floodplain). On the other hand, they confirm the regional extension of As contamination in Nhecolandia's alkaline waters with some values above 3 mg L-1. Arsenic is mainly in the arsenate form, and increases with the evaporation process estimated from sodiumion concentrations. The pH of soil solution and surface water increases rapidly during evapo-concentration up to values above 9 or 10, preventing adsorption processes on oxides and clay minerals and promoting the retention of dissolved arsenic in solution. Solutions from organic soil horizons show higher As contents in relation to Na, attributed to the formation of ternary complex As-(Fe/Al)-OM. In this alkaline pH range, despite high levels of dissolved As, soil horizons and lake sediments in contact with these waters show As values that correspond to uncontaminated environments. (C) 2019 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 11/12770-0 - Soil and water processes at the upper Paraguay basin, Pantanal Wetland
• Grantee: Sonia Maria Furian
• Support type: Regular Research Grants
• FAPESP's process: 13/09192-0 - Saline lakes in the Pantanal of Nhecolândia: Hydro-bio-geochemistry of a singular wetland
• Grantee: Laurent Barbiero
• Support type: Regular Research Grants
• FAPESP's process: 17/23301-7 - Soil and surface water alkaline systems in the Nhecolândia, Pantanal: Hydro-biogeochemical functions
• Grantee: Janaina Braga Do Carmo
• Support type: Research Grants - Visiting Researcher Grant - International
• FAPESP's process: 16/14227-5 - Climatic changes and environmental impacts in wetlands of Pantanal region (Brazil): quantification, control factors and long term temporal modeling
• Grantee: Adolpho José Melfi
• Support type: Research Program on Global Climate Change - Thematic Grants