Hydrochemical and multi-isotopic insights into the genesis model of the karst groundwater system (Southwestern China)

abstract

The Karst groundwater system affected by coal-mining activities is complicated, hampering the sustainable management of groundwater resources. In this study, hydrochemical methods, multivariate statistical methods, and multi-isotope tracing techniques were integrated to clarify the genesis of the karst groundwater system in the Sichuan Basin, southwestern China. Three clusters of groundwater samples were identified in the study area. The hydrochemical type of Cluster I and Cluster II waters was mainly HCO3-Ca type, and hydrochemical type of Cluster III water was dominated by HCO3·SO4-Ca type. The main processes dominating hydrochemical compositions consist of sulfide oxidative dissolution, carbonate dissolution, positive cation exchange, and human activities. The oxidation of sulfides exposed to air and water during coal mining is the primary source of the elevated SO42¿ concentrations. Positive cation exchange resulted in higher Na¿ concentrations, and agricultural activities added NO3¿, Cl¿, and K¿ ions to the aquifers. Atmospheric precipitation was the major recharge source. Groundwater is also influenced by evaporation and mineral dissolution. This study developed a hydrogeological conceptual model for the basin karst groundwater system within coal-mining activities. These findings provide valuable information for the sustainable development of karst groundwater resources. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.