Sources of antimony contamination and its migration into water systems of Xikuangshan, China: Evidence from hydrogeochemical and stable isotope (H, O, S, and Sr) signatures

Abstract

The Xikuangshan (XKS) mine was selected for a comprehensive Sb-related hydrogeochemical study because of its significant Sb contamination in water systems. Hydrochemical data, specifically multi-isotope (H, O, S, and Sr) data, were conducted to elucidate the primary sources and migration processes of Sb responsible for water system contamination. At the XKS Sb mine, water is near-neutral to alkaline and is characterized by high concentrations of SO42− and Sb. Sb occurs as Sb(OH)6− (the dominant species) in these oxidized waters. The hydrochemistry is mainly controlled by carbonate dissolution and silicate weathering. δ2HH2O and δ18OH2O values indicate that the infiltration recharge of mine water and mining activities regulate the migration of Sb in groundwater. δ34SSO4 and δ18OSO4 values indicate that dissolved SO42− and Sb primarily come from stibnite oxidation, bacterial SO42− reduction has either not occurred or is extremely weak, and the reductive dissolution of Fe (III) hydroxides does not significantly affect Sb migration in water. The 87Sr/86Sr ratios further indicate that the discharge of solid mine wastes leaching and smelting water is a crucial source of Sb contamination in groundwater. In addition, the relationship between δ34SSO4 and δ87Sr values suggests the complexity of the contamination source and migration of Sb in water. Finally, a robust conceptual hydrogeochemical model was developed using isotopic tools in combination with detailed hydrogeological and hydrochemistry characterization to describe the contamination source and migration of Sb in water systems at the XKS Sb mine.