Qiao Wen, Wang Yi, He Peiyong, Yin Xiulan, Zhang Deqiang, Bai Guangyu, Sun Wei, Luo Zhigang, Wei Xin, Lan Jianmei, Kersten Michael, Gao Zhipeng, Guo Huaming
MNR Key Laboratory of Mine Ecological Effects and Systematic Restoration, China Institute of Geo-Environment Monitoring, China Geological Survey, Beijing 100081, PR China.
Key Laboratory of Groundwater Conservation of MWR & School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, PR China.
Water Res. 2025 Apr 1;273:123086. doi: 10.1016/j.watres.2024.123086. Epub 2025 Jan 1.
Sulfide mineral oxidation has been recognized as the key driver of arsenic (As) and antimony (Sb) mobility in mining-impacted groundwater. However, the role of carbonate and silicate weathering and secondary mineral precipitation in this process remain unknown. A comprehensive geochemical study of groundwater was conducted in an Sb-mining area, Hunan, China, with samples collected from aquifers of the Xikuangshan Formation (Dx), the Shetianqiao Formation (Ds ), and the Lower Carboniferous Formation (Cy). Results show co-enrichment of dissolved As and Sb with concentrations reaching up to 28.8 and 22.1 mg/L, respectively. The significant positive correlation between SO and As or Sb concentrations, coupled with the similarity of δS-SO to δS signature of sulfide minerals (e.g., arsenopyrite and stibnite), indicate sulfide mineral oxidation as the primary mobilization mechanism. The significantly higher SO concentrations support more extensive sulfide mineral oxidation in the Ds aquifer than those in the Dx and Cy aquifers, which was responsible for its significantly higher As and Sb concentrations. The SO/Σ against Ca/Σ cross plot suggests that, in addition to sulfide mineral oxidation, silicate weathering was more prevalent in the Ds groundwater, which may contribute to enhance As and Sb mobility. However, carbonate dissolution triggered by sulfide mineral oxidation dominated in the Cy groundwater with significantly higher Ca/Σ, favoring the precipitation of pharmacolite (CaHAsO:2HO) and CaSbO, which acted as important sinks for dissolved As and Sb. This study highlights that, in addition to sulfide mineral oxidation, the carbonate and silicate weathering and precipitation of As and Sb-bearing minerals are also pivotal in influencing the As and Sb mobility in groundwater from a mining area.
硫化物矿物氧化被认为是受采矿影响的地下水中砷（As）和锑（Sb）迁移的关键驱动因素。然而，碳酸盐和硅酸盐风化以及次生矿物沉淀在这一过程中的作用仍不清楚。在中国湖南的一个锑矿区开展了一项地下水综合地球化学研究，从锡矿山组（Dx）、蛇田桥组（Ds）和下石炭统（Cy）的含水层采集了样本。结果显示溶解态As和Sb共同富集，浓度分别高达28.8和22.1mg/L。SO与As或Sb浓度之间显著的正相关关系，以及δS-SO与硫化物矿物（如毒砂和辉锑矿）的δS特征相似，表明硫化物矿物氧化是主要的迁移机制。Ds含水层中显著更高的SO浓度表明其硫化物矿物氧化比Dx和Cy含水层更为广泛，这导致了Ds含水层中As和Sb浓度显著更高。SO/Σ与Ca/Σ的交叉图表明，除了硫化物矿物氧化外，硅酸盐风化在Ds地下水中更为普遍，这可能有助于提高As和Sb的迁移性。然而，在Ca/Σ显著更高的Cy地下水中，由硫化物矿物氧化引发的碳酸盐溶解占主导地位，有利于羟砷钙石（CaHAsO₂·2H₂O）和CaSbO的沉淀，它们是溶解态As和Sb的重要汇。本研究强调，除了硫化物矿物氧化外，碳酸盐和硅酸盐风化以及含As和Sb矿物的沉淀在影响矿区地下水中As和Sb的迁移性方面也至关重要。
