Tracing metal trails: unraveling heavy metal pollution, transport pathways, and health impacts in an iron-ore region of Southwest China

Heavy metals (HMs) pollution in mining areas poses significant threats for environmental integrity and public health, yet the transport pathways of HMs from mining wastes remain inadequately characterized. This study assessed contamination levels and human health risks of nine HMs across multiple environmental media within a small catchment in an iron-ore region and identified HM migration pathways from tailings using Pb isotopic tracing. Cd and Sb exhibited the highest contamination, while Zn, Pb, Mn, Cu, and Fe showed moderate enrichment, and Cr and Ni were relatively low. Pollution was most severe in tailings, ore mountain soils, and suspended particles, moderate in sediments and dust, and no-to-moderate in farmland soils. Although anthropogenic activities primarily contributed to HM sources, iron-ore mining had a limited impact on surrounding metal pollution. Over 80% and 50% of Pb accumulation in ore mountain soils and suspended particles were derived from the tailings, respectively, suggesting sediment transport as the main migration pathway of Pb in the region. Noncarcinogenic risk of HMs was acceptable for adults but exceeded safe levels for children in tailings, ore mountain soils, and suspended particles. Additionally, carcinogenic risk from Cr surpassed acceptable thresholds for both adults and children across all samples. These findings highlight the necessity for long-term monitoring of HMs in the orefield and urgent management of HM migration via riverine transport to mitigate potential pollution risks.