Geochemical Study of the Groundwater from Coal Bearing Aquifer in Zhuxianzhuang Coal Mine, Northern Anhui Province, China

Major ion concentrations were measured in 22 groundwater samples collected from a coal bearing aquifer in Zhuxianzhuang coal mine, northern Anhui Province, and the ion source and geochemical characteristics were discussed by the methods such as traditional graphic and multivariate statistic analysis. The results showed the presence of three water types, i.e., HCO₃-Na, Cl-Na and SO₄-Na. The surrounding rock weathering and evaporation, both controlled the chemical characteristics of groundwater, evidenced by the Gibb’s diagrams. In detail, the features of ion ratios such as Ca/Na, HCO₃/Na and Mg/Na show that the evaporate dissolution and silicate weathering were the dominant water-rock interactions. Multivariate analysis, such as correlation analysis, cluster analysis and FA analysis were also conducted to reveal the ion source in groundwater, and the Ca²⁺ and Mg²⁺ were mainly released from the dissolution of gypsum and/or magnesium and/or anorthite; while the Na⁺ is influenced by the weathering of feldspar and halite, with the cation exchange in a certain extent. In contrast, the Cl^-, HCO₃^- and SO₄^2- are also controlled by the halite dissolution, silicate mineral weathering and sulphate mineral dissolution, respectively. In addition, the SO₄^2- in groundwater could be influenced by the oxidation of pyrite, which is abundant in the coal bearing aquifers.