[Hydrochemical Characteristics and Variation in Karst Groundwater in the Baiquan Spring Area of Xingtai Over the Last 30 Years].

To elucidate the variation patterns in the hydrochemical characteristics of karst groundwater in the Baiquan Spring area of Xingtai over the past 30 years, an integrated approach utilizing mathematical statistics, Piper trilinear diagrams, Gibbs diagrams, and ion ratio analyses was employed. Comparative analysis was conducted on 62 sets of karst water samples collected during the dry seasons of 1991 and 2020. The findings indicated that the groundwater in the spring area was generally weakly alkaline with a low salinization degree, predominantly characterized by Ca²⁺ and HCO₃^- as the dominant ions. Compared to that in 1991, the alkalinity of groundwater in 2020 had intensified, with a general increase in the concentration of various indicators. The hydrochemical types had shifted from the relatively concentrated HCO₃-Ca and HCO₃-Ca·Mg types to a broader spectrum of types, gradually exhibiting a salinization trend. The distribution characteristics of exceeding components such as TDS, Na⁺+K⁺, SO₄^2-, and F^- showed significant spatial differences. Rock weathering played a pivotal role in the changes observed in the hydrochemical components of groundwater, with enhanced cation exchange and evaporation processes further influencing the hydrochemical characteristics and their spatial distribution.