Search

The Xikuangshan (XKS) mine, an antimony mine that has been active for more than a century, was chosen for a detailed antimony hydrogeochemical study because of the historical antimony contamination in local bedrock aquifers. Hydrochemical data, δ34S values of dissolved SO 4 2−, and δ98Mo values were analyzed to identify the predominant geochemical processes affecting Sb attenuation within the aquifers. Groundwater from the adits at the XKS Sb mine reflects an oxidizing environment and has pH values between 6.81 and 8.89 because of the sufficient acid-neutralizing effect of carbonates. The decrease in Sb concentrations along the groundwater flow direction and the highly coloured deposits in the adits indicate Fe and Mn oxides have a significant capacity for Sb sorption. The δ34S values of the groundwater indicate that reductive dissolution of Fe(III) hydroxides is not the dominant process controlling Sb mobilization. Furthermore, the δ34S values and weak-alkaline groundwater corporately suggest that Sb adsorption on and desorption from Fe/Mn (hydr)oxides may both occur, with adsorption being more significant than desorption with respect to Sb attenuation in groundwater. The δ98Mo values of the groundwater further demonstrate that this adsorption is relatively significant in terms of Sb attenuation, and that competitive adsorption may occur between Sb and As in groundwater at the XKS Sb mine. Overall, the hydrochemistry analysis, especially the S and Mo isotope evidences collectively elucidate that the attenuation of Sb in groundwater from the XKS Sb mine are influenced by several geochemical processes, including: (1) more adsorption on than desorption from Fe/Mn (hydr)oxides; (2) competitive adsorption of arsenic; and (3) dilution with low-Sb groundwaters. This study demonstrates that hydrochemical analyses, particularly S and Mo isotope studies, are useful for tracking Sb attenuation in groundwater from antimony-contaminated mine areas. [Display omitted] • S and Mo isotopes were used to elucidate the attenuation of Sb in bedrock aquifer. • Adsorption on Fe/Mn (hydr)oxides is relatively significant in terms of Sb attenuation. • A competitive adsorption may occur between Sb and As. • A conceptual model of Sb attenuation in bedrock aquifer system was proposed. [ABSTRACT FROM AUTHOR]

The antimony (Sb) content of shallow drinkable groundwater at Xikuangshang mine area (in Hunan province, China) has exceeded China's national drinking water quality guidelines, posing a serious threat to the health of residents in the mine area. The difference in hydrogeochemistry characteristics and water-rock interactions between low Sb groundwater (<0.015 mg/L) and high Sb groundwater (>0.015 mg/L), however, remains unclear. In this study, 24 samples were collected from shallow drinkable groundwater at the mine area. The hydrogeochemistry data and water-rock interactions were analyzed to reveal the condition leading to the formation of high Sb groundwater. Compared with low Sb groundwater, high Sb groundwater has a higher level of Na+, TDS, and SO 4 2-, which increase by 6.38, 1.84, and 4.04 times, respectively. The low Sb groundwater is mainly controlled by Ca–HCO 3 –SO 4 type, whereas the high Sb groundwater is controlled by Ca–HCO 3 –SO 4 type as the main facies, and Ca–Na–SO 4 type and Ca–SO 4 –HCO 3 type as the secondary facies. The chemical composition of low Sb groundwater is mainly influenced by the dissolution of carbonate minerals and the chemical composition of high Sb groundwater is controlled by ion-exchange interaction and dissolution of carbonate minerals and silicate minerals, among which ion-exchange interaction is the most important factor. The outcomes of this research provide a better understanding of the mechanisms of Sb pollution in groundwater and it will help in securing safe drinking water sources for local communities. • Geochemistry characteristics are analyzed between low and high Sb groundwater. • Ion-exchange interaction is the most important factor for high Sb groundwater. • Part of high Sb groundwater have reached water-silicate equilibrium. • The mechanisms of Sb pollution in shallow groundwater of Xikuangshang mine area. [ABSTRACT FROM AUTHOR]