Integrated source apportionment and risk assessment prioritizes heavy metal control at an abandoned antimony smelter

Mining and smelting constitute primary anthropogenic sources of persistent heavy metal (HM) contamination in soils, posing severe ecological and health threats globally. Conventional risk assessment often fails to discriminate between natural weathering inputs and anthropogenic emissions while struggling to prioritize pollution sources by risk severity, hindering targeted remediation. This study overcomes these limitations by integrating positive matrix factorization (PMF) source apportionment with ecological risk assessment (ERA) and health risk assessment (HRA) frameworks to quantify source-specific risks. Applied to soils surrounding an abandoned antimony smelter in Gansu Province, HM concentrations (excluding Cr and Ni) exceeded background levels, with Sb reaching 935.28 mg/kg. Extreme pollution by Sb and Cd was observed, while 95% of samples showed moderate to heavy contamination levels. PMF identified four primary pollution sources: industrial activities (27.82%), mining (30.43%), natural sources (21.11%), and transportation (20.64%). ERA indicated extreme ecological risks attributable primarily to Sb, Cd, and Hg, with substantial contributions from industrial (50.11%) and mining (31.83%) origins. HRA revealed unacceptable non-carcinogenic (24.90 for children, 4.06 for adults) and carcinogenic risks (1.83 × 10^-4 for children, 1.11 × 10^-4 for adults). Ingestion served as the predominant exposure pathway, primarily from Sb and As for non-carcinogenic risks and carcinogenic risks, respectively. Integrated risk apportionment demonstrated dominant non-carcinogenic risk contributions from mining (53.33%) and industrial (43.62%) activities primarily via Sb, while industrial (36.60%) and natural (35.81%) sources were major carcinogenic risk contributors with Ni and Cd as the key contaminant. This quantitative source-risk linkage provides a science-based foundation for prioritising control measures and enabling safe reclamation of polluted industrial sites.