Seasonal characterization, sources, and source-specific risks of PM 2.5 bound PAHs at different types of urban sites in central China

Polycyclic aromatic hydrocarbons (PAHs) have been extensively investigated in China. However, most previous studies only focused on specific locations. Here, we conducted field studies simultaneously to explore the seasonal characterization, sources, and source-specific risks of 16 PAHs in four polluted cities in China. Similar seasonal Σ16 PAHs variations are observed in all four sites with relatively high values in winter and low values in summer and the ratios of Σ16 PAHs between winter and summer range from 2.7 to 4.4. From summer to winter, the extent of PAH increase outpaces that of PM 2.5 increase resulting in significant increase of ∑16 PAHs/PM 2.5 in winter. Five potential sources were resolved by PMF: (1) coal combustion (32–52%); (2) vehicle emissions (19–29%); (3) evaporation (9–26%); (4) coke oven emission (11–15%); and (5) biomass burning (5–13%). The highest fraction of evaporation is found in the Luoyang site due to the presence of many petrochemical plants, the largest oil refinery in Henan and large oil storage tanks. The coking factor contributes the largest proportion in Anyang site because of many out of date inefficient coking facilities. The source-related risks in four sites are all higher than the USEPA guideline value (1.0 × 10 −6 ) except for biomass burning. The largest total risks are observed at Luoyang site, slightly higher than those of other cities. Our results suggest that the PAHs still need to be concerned due to the complexity of sources and source emitted risks in different type of cities, and specific source control strategies should be target in different regions.