Health risk assessment and source apportionment of heavy metals in soils of the largest volcanic island in China based on Monte Carlo simulation and PMF model

Naozhou Island represents China's largest volcanic island. Socioeconomic development has driven increased tourism, agriculture, and fisheries activities on the island. Potential health threats posed by soil heavy metals (HMs) are becoming a growing scientific concern. Surface soil samples from 218 sites across the island were analyzed for eight HMs (Hg, As, Cr, Cu, Pb, Zn, Cd, and Ni), with subsequent evaluation of their pollution characteristics and associated health risks. Results identified Ni, Cd, and Cr as the predominant enriched pollutants, with Ni and Cd exhibiting elevated potential ecological risks. The integrated application of PMF modeling and HMs correlation analysis effectively identified four pollution sources: natural sources, industrial production, traffic emissions, and agricultural activities, with quantified contribution rates of 62.2%, 6.3%, 15.5%, and 15.9%, respectively. Health risk assessment based on soil HMs concentrations revealed measurable non-carcinogenic and carcinogenic risks across all population groups, with total carcinogenic risk (TCR) remaining at elevated levels. Ubiquitous TCR exceedances (>1.00E-06) were observed, identifying children as a vulnerable subpopulation with significantly elevated health risks relative to adults. Agricultural and traffic emissions emerged as dominant anthropogenic risk drivers in source-resolved health assessments, significantly increasing risks across all demographic groups. These findings offer targeted scientific support for HMs pollution mitigation in volcanic island soils.