[Seasonal Variation, Source Identification, and Health Risk of PM_2.5-bound Metals in Xinxiang]

This study analyzed the seasonal variation, sources, and source-specific health risks of PM_2.5-bound metals in Xinxiang city, Henan province. A total of 112 daily PM_2.5 samples were collected over four consecutive seasons during 2019-2020. In total, 19 elements were identified using inductively coupled plasma atomic emission spectroscopy (ICP-AES). The annual concentrations of PM_2.5 and 11 heavy metals were calculated to be (66.25±35.73) μg·m^-3 and (1.32±0.84) μg·m^-3, respectively. Strong seasonal variations were observed in PM_2.5 concentrations and the concentrations of associated metal elements, with the lowest concentrations all occurring in summer. The highest concentrations of dust-related elements (e.g., Al, Ca, Fe, Mg,and Ti) were recorded in spring, differing significantly from other elements, which all exhibited the highest mass concentrations in winter. The results apportioned from positive matrix factorization (PMF) and potential source contribution function (PSCF) models showed that the major sources of PM_2.5-bound elements were Ni-and Co-related emissions (5.8%), motor vehicles (13.7%), Cd-related emissions(5.1%), combustion emissions (18.2%), and dust (57.3%). Health risk models showed that there were no obvious non-carcinogenic risks associated with these metals, because their hazard quotient (HQ) values were all below 1. Lifetime carcinogenic risks of the five apportioned sources were all higher than the acceptable level (1×10^-6). Of these five sources, combustion emissions were the largest contributors to cancer risk (8.74×10^-6, 36.9%) and non-cancer risk (0.60, 25.6%). This study suggests that control strategies to mitigate exposure risk in Xinxiang should emphasize reducing the sources of combustion emissions.