[Recharge Sources and Hydrochemical Evolution Mechanism of Surface Water and Groundwater in Typical Karst Mining...

To study the recharge source, hydrochemical characteristics, and evolution process of karst underground water and surface water in the Xianghualing Mining area, we collected 32 groups of samples from karst underground water and surface water sources in and around the mining area. Based on multivariate statistical analysis, the Piper three-line diagram, Gibbs diagram, and ion ratio coefficient, this study analyzed the hydrogeochemical characteristics of karst underground water and surface water in the Xianghualing Mining area. The study systematically revealed the recharge source, recharge age, and hydrochemical evolution law of both water sources. The results showed that the karst underground water and surface water in the Xianghualing Mining area were weakly alkaline, with the main anions being HCO₃^- and the main cations being Ca²⁺. The hydrochemical types mainly included HCO₃-Ca, HCO₃-Ca·Mg, and HCO₃·SO₄-Ca·Mg types. Atmospheric precipitation was the primary source of recharge for karst underground water and surface water, and it was also influenced by evaporation during the runoff process. However, the evaporation effect of karst groundwater was relatively small, which was closely related to modern hydrology, and the cycle replacement process was more rapid. The hydrochemical evolution characteristics of karst underground water and surface water were mainly affected by rock weathering, cation exchange adsorption, mineral dissolution, and human activities （such as agricultural and mining activities）. Ca²⁺, Mg²⁺, and HCO₃^- were primarily derived from the dissolution of carbonate minerals, with a small portion also originating from the weathering and dissolution of silicate minerals. Na⁺ and Cl^- were primarily derived from the dissolution of rock salts. Among them, Cl^-, NO₃^-, and SO₄^2- were greatly affected by external inputs from agricultural activities, domestic sewage discharge, and mining activities. The research results are of great significance to the cyclical evolution process of karst underground water and surface water, as well as the protection and utilization of water resources in the Xianghualing Mining area.