Historical contamination with a current problem: Can mining tailings enhance coastal arsenic pollution?

The coast of Espírito Santo state (Southeast Brazil) is recognized for its environmental arsenic (As) enrichment and, over the years, mining operations have potentialized it. We aimed to evaluate the effect of Rio Doce discharge on As inputs and the role of iron ore tailings from the Fundão dam disaster in enhancing As contamination in the marine sediment. Two scenarios were evaluated: Predisaster and Postdisaster; dry and wet conditions were considered in each period. High As concentrations were found in the Predisaster (28.44 ± 13.53 µg g−1), but a significant increase in As was remarkable during the Postdisaster in the wet season, one year after the disaster (maximum of 58.39 µg g−1; geoaccumulation index (Igeo) Class 3, moderately severe pollution). On that occasion, iron (Fe) oxy‐hydroxides from tailings were remobilized from the Rio Doce channel and deposited on the continental shelf bottom. Therefore, chemical interactions among Fe, As, and carbonates were enhanced, resulting in As and Fe coprecipitation and the trapping by carbonate adsorption. Rio Doce discharge seems to be the main factor in As inputs to the inner continental shelf when flooding do not occur previously in samplings, which allows further dispersion of contaminants, although this hypothesis should be tested further. Integr Environ Assess Manag 2024;20:159–168. © 2023 SETAC Key Point: Arsenic contamination of marine sediments was studied before and after the rupture of a mining tailings dam (Fundão dam disaster).Arsenic concentrations increased from moderate (Predisaster) to moderately severe pollution levels (Postdisaster) one year after the disaster.Iron oxy‐hydroxide inputs from iron ore tailings probably explain the accumulation of As in sediments by coprecipitation of As and Fe and deposition by carbonate adsorption.River discharges did not increase As concentrations in sediment during the initial stages after the disaster (twenty days and two months after). [ABSTRACT FROM AUTHOR]