Evolution of hydrogeochemistry driven by groundwater and surface water transformation in Jinan Spring Catchment

The implementation of multi-source ecological water replenishment represents a critical strategy to address karst spring water conservation and supply issues. With the context of ecological water replenishment, studying the chemical evolution of groundwater is of great significance for protecting the groundwater environment and evaluating the ecological benefits of such replenishment. This study employs hydrogeochemical and multivariate statistical analysis methods to investigate the evolution patterns of groundwater chemical composition under ecological water replenishment conditions in Jinan Spring Catchment (JSC). It reveals the hydrogeochemical behaviors and characteristic components induced by multi-source water replenishment. The results indicate that the primary sources of groundwater are atmospheric precipitation infiltration and Yufu River leakage. Along the groundwater runoff path, as the distance from the Yufu River increases, the δ 18 O values of groundwater gradually decrease and approach the atmospheric precipitation line, suggesting that the basin is a strong leakage zone with intense surface water-groundwater interaction. Controlled by carbonate rocks, the hydrochemical types during both rainy and dry seasons are predominantly HCO 3 ·SO 4 -Ca. The correlations between the total dissolved solids (TDS) and Ca 2+ and SO 4 2− in groundwater are most significant, with correlation coefficients of 0.9 and 0.91 during the dry season, and 0.83 and 0.8 during the rainy season, indicating that TDS mainly originates from Ca 2+ and SO 4 2− . Inverse geochemical modeling results show that along the G10→G21 groundwater runoff path, calcite, dolomite, gypsum, halite, Ca-montmorillonite, and quartz dissolved, while K-feldspar, albite, anorthite, illite, and CO 2 precipitated. Along the G3→G20 path, dolomite, gypsum, halite, K-feldspar, Ca-montmorillonite, quartz, and CO 2 dissolved, while calcite, albite, anorthite, and illite precipitated. Along the G7→G22 path, calcite, dolomite, gypsum, halite, K-feldspar, Ca-montmorillonite, and quartz dissolved, while albite, anorthite, illite, and CO 2 precipitated, demonstrating differences in water-rock interactions along different groundwater runoff paths.