Integrated assessment and forecasting of heavy metal contamination in soils affected by Pb–Zn mining in Guizhou, China

Heavy metal contamination in soils surrounding Pb–Zn mining areas poses persistent ecological and public health risks in Guizhou Province, China. However, ecological risk transfer among ecosystem compartments and the future decline in soil environmental capacity remain poorly understood. This study investigated heavy metals in surface soil (0–20 cm) and subsoil (20–60 cm) around a Pb–Zn mining area in Shuicheng District, Liupanshui City, by integrating the geo-accumulation index (Igeo), pollution load index (PLI), potential ecological risk index (PERI), network environ analysis (NEA), Monte Carlo health-risk assessment, and dynamic environmental-capacity forecasting. This framework characterized contamination levels and human-health risks, traced the redistribution of ecological risk among trophic components, and evaluated the future decline of residual soil buffering capacity under continued pollution pressure. The results revealed severe contamination by Pb, Cd, and Zn in both surface and subsurface soils, with Pb showing the highest pollution intensity. PERI classified most sampling sites as moderate to high ecological risk. The NEA model further showed that Pb, Zn, and Cd generated the highest ecological pressures across trophic levels and that soil microorganisms were the major ecological risk sink, accounting for 66.4% of integrated ecosystem risk, followed by vegetation, herbivores, and carnivores. Health risk assessment indicated markedly higher non-carcinogenic and carcinogenic risks for children than adults, primarily due to Pb and As exposure. Dynamic capacity forecasting suggested a rapid reduction in the residual soil environmental capacity over the next 10 years, especially for Hg. These findings support remediation planning, land-use management, and exposure reduction in mining-affected areas.