Seasonal pollution characteristics, source apportionment and health risks of PM2.5-bound polycyclic aromatic hydrocarbons in an industrial city in northwestern China

PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) have attracted considerable attention due to their carcinogenicity to humans. As the "copper city" of China, Baiyin has unique natural geographical conditions, but there have been few studies on PM2.5-bound PAHs pollution characteristics. Therefore, the pollution characteristics, sources and health risks of PM2.5-bound PAHs in Baiyin were studied over a one-year period. The average annual PAHs concentration was 67.4 +/- 34.7 ng/m(3), with the highest PAHs concentration in winter and the lowest in summer. Based on a positive matrix factorization (PMF) model, the main PAHs sources were coal, a mixed source of petroleum volatilization and natural gas and biomass combustion, gasoline exhaust, and diesel exhaust. Spring and winter were dominated by coal combustion, while summer and autumn were dominated by gasoline exhaust. Backward trajectory analysis showed, that the largest pollution contribution came from the local area throughout the year, followed by northern Mongolia in spring, northeastern Xinjiang in summer, and Qinghai in autumn and winter. A human carcinogenic risk assessment based on a health model indicated that PAHs emissions should be controlled in seasons other than summer, especially when there is a risk of ingestion and dermal contact.