Hydrochemical characteristics and influencing factors of typical karst groundwater in Southern Sichuan, China

ABSTRACT This study investigates the hydrochemical characteristics and controlling factors of karst groundwater in southern Sichuan, China, to assess its quality and identify the sources of major ions. A total of 19 groundwater samples were collected and analyzed using mathematical statistics, Piper and Gibbs diagrams, and ion correlation analysis. The results show that the groundwater is predominantly fresh and weakly acidic, with HCO3-Ca as the primary hydrochemical type. However, a key finding is the high spatial heterogeneity of the hydrochemical system. The relatively low variation in Ca2+ concentrations underscores the pervasive influence of carbonate rock dissolution as a regional background process. In contrast, the extremely high variability of Na+, Cl−, and SO42− highlights significant contributions from localized influences. Correlation and cluster analyses confirm that groundwater chemistry is predominantly controlled by water–rock interaction, but also identify a subset of samples distinctly affected by anthropogenic activities (e.g., domestic wastewater and agriculture). In summary, groundwater evolution is governed by a regional baseline of carbonate weathering, upon which are superimposed highly variable localized influences. This study provides a critical scientific basis for the differentiated protection and sustainable management of water resources in karst regions.