Fractionation of heavy metal(loid)s and PAH contamination in urban park surface dust: implications for children's health risk.

Urban parks are important public environments where children may be exposed to multiple contaminants through frequent contact with surface dust. However, the cumulative health risks associated with combined exposure to heavy metal(loid)s (HMs) and polycyclic aromatic hydrocarbons (PAHs) remain insufficiently understood, as these contaminants are often assessed separately, and the health risks of HMs are commonly evaluated using total rather than fraction-based concentrations. This study integrated multivariate characterization and source apportionment of co-occurring HMs and PAHs, HM geochemical fractionation, and Monte Carlo-based probabilistic health risk analysis to evaluate surface dust collected from different functional zones of urban parks. The results revealed distinct source patterns: PAHs were mainly linked to regional pyrogenic inputs, while HMs were primarily associated with localized abrasion-related activities. Under the lability-informed screening scenario based on operationally defined HM fractions, non-carcinogenic risk estimates were lower than the corresponding estimates based on total concentrations, with the total hazard index (THI) decreasing by ∼60% and remaining below 1 in 99.5% of simulation scenarios. Nevertheless, carcinogenic risk estimates in localized hotspots remained within the 1.0 × 10-6 to 1.0 × 10-4 range, driven primarily by As, Cr, and co-occurring PAHs, particularly in child-frequented recreational areas and localized microenvironments influenced by adjacent traffic. These findings suggest that integrating fraction-based scenarios provides a useful complementary perspective for prioritizing high-concern microenvironments and guiding targeted pollution management in urban parks.