Groundwater Heavy Metal Contamination and Health Risk Assessment: A Case Study of South Dongting Lake, China

To investigate the heavy metal contamination status and associated health risks in the groundwater of South Dongting Lake, China, 88 groundwater samples were collected and analyzed for the contents of heavy metals (Fe, Mn, Cu, Zn, As, Cd, Pb). The heavy metal pollution characteristics and human health risks were comprehensively analyzed using a combined approach of the Heavy Metal Pollution Index (HPI), Heavy Metal Evaluation Index (HEI), Water Quality Index (WQI), and by integrating traditional health risk assessment with Monte Carlo simulation. The results indicated that manganese (Mn) and iron (Fe) were the most prominent pollutants in the regional groundwater, with exceedance rates of 35.3% and 25.0%, respectively. Arsenic (As) showed localized exceedances (13.91 μg/L, 1.39 times the standard limit). Spatially, contamination levels were higher in the north and lower in the south, with Fe, Mn, and As enrichment concentrated in the northern region, correlating with geological structures and industrial discharges. Health risk assessment revealed that the total carcinogenic risk (TCR) for children (1.82 × 10−4) exceeded the safety threshold by 82%, with arsenic being the primary carcinogen (contribution rate: 74.7%). The non-carcinogenic total hazard index (HI) reached 3.59 for adults and 6.54 for children, significantly exceeding the acceptable level of 1.0. Manganese was identified as the core non-carcinogenic risk source (Hazard Quotient (HQ) for children = 3.35). Monte Carlo simulation confirmed that pollutant concentration and exposure time were the most sensitive risk-driving factors. This study provides a scientific basis for prioritizing the control of As and Mn pollution in the northern region and implementing protective measures against children’s exposure.