Spatial and seasonal variation of arsenic speciation in Pantanal soda lakes

Author(s)

Hechavarria-Hernandez, Amauris ; Viana, Jose Lucas Martins ; Barbiero, Laurent ; Rezende-Filho, Ary Tavares ; Montes, Celia Regina ; Melfi, Adolpho Jose ; Fostier, Anne Helene

• Document type: Journal article
• Source: Chemosphere; v. 329, p. 9-pg., 2023-04-17.

Abstract

The occurrence of high arsenic concentrations (up to 3000 mu g L-1) in water of soda lakes of the Pantanal wetland is a remarkable case of natural arsenic contamination in South America. However, little is known about arsenic speciation in this environment, particularly regarding speciation changes related to lake trophic status and seasonal variations. To fill this gap, arsenic speciation analysis was carried out in surface (SW) and subsurface (SSW) waters sampled in five soda lakes with different eutrophication status, in two dry and one wet season. As (V) was the dominant species in these waters, while As(III), DMA, MMA and likely complex organic species were present in lower amounts. The results allow to conclude that the arsenic speciation in SW and SSW varies seasonally according to the regional wet or dry periods and lake water levels. In eutrophic turbid and in oligotrophic vegetated soda lakes, arsenic speciation was also characterized by spatial differences between edge and center or between the SW and SSW. Cyanobacteria or macrophytes/algae are involved in arsenic biotransformation in soda lakes through its metabolic and detoxification processes. Significant variation in surface water arsenic speciation occurs as a result of seasonal primary production fluctuation or water arsenic concentration changes in the soda lakes, increasing organoarsenics in dry periods, whereas in flood periods, As (V) prevails. Spatial distribution of arsenic species is significantly impacted by biogeochemical conditions at the water/sediment interface in soda lakes. (AU)

• FAPESP's process: 19/18124-4 - Fluxes, speciation and bioavailability of arsenic at the water/sediment interface in alkaline lakes of the Pantanal of Nhecolândia using DGT
• Grantee: José Lucas Martins Viana
• Support Opportunities: Scholarships in Brazil - Doctorate
• 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 Opportunities: Research Program on Global Climate Change - Thematic Grants
• FAPESP's process: 21/14272-9 - Circular economies: using DGT to assess the release kinetics of phosphorus in soils treated with waste-based fertilizer alternatives
• Grantee: José Lucas Martins Viana
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate