Impacts of a tailings dam failure on water quality in the Doce river: The largest environmental disaster in Brazil

Abstract

BackgroundOn November 5, 2015, the Fundão Dam, owned by Samarco Mineração SA, experienced a catastrophic failure, releasing approximately 55 to 62 million m3 of mining ore waste into the Doce River. This event had severe consequences as the Doce River serves as a vital source of water and food for numerous communities. ObjectiveEvaluate the spatiotemporal distribution of water parameters before, during, and after the failure of the Samarco tailings dam, with the goal of support the management and restoration of water quality. The study utilizes a long historical series of data from 1997 to 2018. MethodologyIn this study, data from 13,916 measurements of variables including HCO3−, Mg2+, Ca2+, SO42−, pH, EC, and metal(oids) such as Fe, Mn, As, Cu, Ba, Pb, Zn, Cd, Cr, and Ni were compiled. These measurements were collected from 1997 to 2018 to investigate the impact of the dam rupture. ResultsThe dam failure resulted in an increase in high turbidity events and total suspended solids (TSS), leading to a decline in water quality. The Kruskal-Wallis test revealed a homogenization effect along the river watershed caused by the accident, particularly for Pb, Ni, Cd, Cr, and coliforms. Additionally, there was a change in the seasonal distribution of PO43−, NH4+, Na+, SO42−, and Zn. The factor analysis identified four main factors: i) HCO3−, Mg2+, Ca2+, SO42−, pH, and electrical conductivity (37.55%) were indicative of weathering processes from lithotypes; ii) Fe+Mn and the metal(oids) (As, Cu, Ba, Pb, Zn, Cd, Cr, and Ni) (15.89%) were associated with ore waste and regional geology; iii) total coliforms, NO3−, NH4+, and PO43− (9.39%) were linked to anthropogenic influences in the river; and iv) K+, Na+, and Cl− (8.22%) represented the impact of domestic and industrial sewage discharge as well as the marine environment in the lower sector of the Doce River. ConclusionThe dam rupture significantly altered water quality in the Doce River, particularly in relation to metal(oids), three years after the disaster. The presence of ore waste in the bottom sediments creates an environmental liability as it can be remobilized by human activities or extreme weather events, further impacting water quality.