Geological Characteristics and Groundwater Health Risk Assessment in Nanshu Area, Eastern China

Located in eastern China, the Nanshu area is abundant in groundwater resources with favorable water quality, acting as a critical water supply source for the region. In recent years, the regional groundwater environment has been significantly disturbed by continuous anthropogenic activities, which has aroused widespread concern. In this study, correlation analysis, principal component analysis, hydrochemical methods, the Entropy Weight Water Quality Index, and the Human Health Risk Assessment model were comprehensively applied to systematically investigate groundwater in the Nanshu area. The research objectives are to determine the health risk levels of regional groundwater and provide a scientific basis for the protection and rational utilization of groundwater resources. The results indicate that groundwater in the study area is weakly alkaline freshwater, dominated by the HCO3-Ca hydrochemical type. With favorable groundwater circulation conditions and weak evaporative concentration effects, it generally exhibits the typical natural hydrogeochemical characteristics of shallow groundwater in the piedmont regions of northern China. The chemical composition of groundwater is mainly controlled by water–rock interactions. The dissolution of silicate minerals, gypsum, halite and sepiolite, together with significant reverse cation exchange, collectively shape the hydrochemical composition, and natural hydrogeological conditions form the basic pattern of regional water quality. The overall potability of groundwater in the study area is moderate. Approximately 30% of the groundwater is unsuitable for direct drinking due to anthropogenic pollution, and agricultural activities and domestic sewage discharge have become key factors causing local water quality degradation. Non-carcinogenic health risks posed by groundwater nitrate vary significantly among different populations. The risk level for infants and young children is much higher than that for adults, posing a substantial health threat to sensitive populations. According to the findings, it is recommended to focus on controlling the groundwater risk sources in the central area, strengthen the dynamic monitoring of water quality in water source zones, and strictly regulate regional development activities, so as to achieve the sustainable utilization of groundwater resources.