Acidity-dependent mobilization of antimony and arsenic in sediments near a mining area

Coexisting antimony (Sb) and arsenic (As) have raised worldwide concerns, but the factors controlling the mobilization of Sb and As in sediments near mining areas are not fully understood. Herein, multiple leaching methods and complementary spectroscopic analyses were used to investigate the mobility of Sb and As and its controlling factors in sediments around the Xikuangshan tailings pond over a wide range of acidity. The general acid neutralizing capacity (GANC) test showed that the leachability of Sb and As exhibited a V-shape pattern with a minimum concentration at 1.6 eq H⁺/kg. The result of MINTEQ simulation agreed well with our GANC results, and demonstrated that the decrease of Sb and As in the range 0-1.6 eq H⁺/kg and the increase in 1.6-4 eq H⁺/kg were mainly controlled by the adsorption and dissolution of iron oxyhydroxide, respectively. Based on the V-shaped leaching trend, Sb and As were predicted to be immobilized in sediments when the acidity accumulated to 1.6 eq H⁺/kg for a long term up to 61 years. This study provides insights in assessing the leaching risks and predicting the mobilization of Sb and As in sediments.