Impacts of acid mine drainage remediation in the largest gold mine of Latin America on natural water bodies in the Dominican Republic

Impacts of the acid mine drainage (AMD) remediation are investigated on the largest gold mine in Latin America, located in the Dominican Republic. Geochemical analysis of suspended matter in water performed in 2022 on water bodies located downstream to the mine, namely, the Margajita River and Lake Hatillo, are compared with analyses made in 2007, before the AMD remediation. The results for the Margajita River show a strong decrease in heavy metal and metalloid concentrations in the dissolved phase for Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Sb, and Pb (between 89.1 and 99.9%) which is correlated with a pH neutralization (from a pH of 2 to 7.5). However, the concentrations of Cd and sulfate in the dissolved fraction remain higher than their environmental standard values, and a high concentration of K is also observed. High contributions in terms of mass are identified for Cs, Tl, Cd, and Li in the Margajita River. Concentrations of Al, Fe, Ni, Zn, and As in suspended sediments are higher than the environmental standard values in 2022. Modeling of the chemical speciation shows that the higher pH leads to the formation of suspended particles in the form of hydroxides and sulfates. The concentrations in suspended sediments are highly correlated between Margajita River and Lake Hatillo in 2022 for Fe, Cd, Li, and Ca (R² between 0.9 and 0.99 with p ≤ 0.05). In Lake Hatillo, principal component analysis shows that invariant elements Fe, P, Ti, Zr, and Al are correlated, as they precipitate between the inlet and outlet of the lake.