New insights into metal(loid) dynamics in the Doce River estuary (Brazil) after a massive iron ore-processing tailing dam collapse.

The present study investigated metal and metalloid dynamics in the estuarine water of the Doce River (Brazil) after the collapse of an iron ore-processing tailing dam in 2015. Spectroscopic and isotopic techniques were applied to bring new insights into the effects of the dam failure on the dynamics and hazardousness of particulate and dissolved metal(loid) concentrations along the fluvial-estuarine continuum. Spectroscopic analysis showed that the suspended particulate matter (SPM) of the Doce River estuary consisted of a combination of soil-delivered particles and fine tailing mud particles with small amounts of coarse tailing mud Fe oxides (~150-µm width). Enrichment and contamination factors showed that the dam failure increased particulate Fe, Pb, Cd, and As, and dissolved Pb concentrations. Total concentrations of As (15 µg/L), Pb (30 µg/L), Cd (8 µg/L), and Cr (105 µg/L) increased up to values higher than quality and regulatory guidelines. Human health risk assessment showed that local communities are exposed to a potentially chronic Cr noncarcinogenic effects, although Cr high concentrations were not linked with the dam failure by this study. The particulate Pb isotope signatures reported herein (206/207Pb ratios of 1.214 ± 0.006 and 208/206Pb ratios of 2.025 ± 0.011) can be applied to constrain metal(loid) sources in the Doce River sediment plume and continental shelf. The river-ocean mixing zone caused abrupt changes metal(loid) partitioning (Zn, Pb, Cr, Cu, Cd, and As), controlling their fate in the estuary and the Brazilian southeast coastal.