Sources analysis and risk assessment of heavy metals in soil in a polymetallic mining area in southeastern Hubei based on Monte Carlo simulation

This study investigates the pollution characteristics, spatial patterns, causes, and ecological risks of heavy metals in the soils of the southeastern Hubei polymetallic mining areas, specifically the Jilongshan (JLS) and Tonglushan (TLS) regions, located in the middle and lower reaches of the Yangtze River. The main findings are as follows: (1) Among the heavy metals present in the soil, copper (Cu) has the highest average concentration at 278.54 mg/kg, followed by zinc (Zn) at 161.16 mg/kg, chromium (Cr) at 75.23 mg/kg, nickel (Ni) at 30.38 mg/ kg, arsenic (As) at 22.53 mg/kg, cadmium (Cd) at 0.76 mg/kg, and mercury (Hg) at 0.14 mg/kg; (2) The distribution of heavy metal concentrations exhibits significant regional variations, with the spatial pattern of pollution indicating that TLS is more affected than JLS, as evidenced by the Pollution Load Index (PLI) values; (3) Three potential sources of heavy metals were identified: natural sources, anthropogenic activities (including industrial production and agricultural practices), and atmospheric deposition (both dry and wet); (4) While severe contamination levels of specific metals such as copper and cadmium are observed in JLS and TLS soils, the overall contamination is mild, suggesting complex contamination dynamics; (5) Cadmium poses a moderate to high ecological risk, being the most sensitive factor in the comprehensive ecological risk assessment with a contribution rate of 65.2 %; (6) The concentrations of heavy metals in the soil present certain health risks, with children being more vulnerable than adults. This study helps to identify the hot spots and pollution patterns of heavy metal pollution in polymetallic mining areas and provides a theoretical basis for the study of local countermeasures against pollution. Based on the research results, management measures and ecological restoration suggestions are proposed, which are important for reducing soil insecurity and coping with climate change.