Characterization and source identification of PM_2.5-bound polycyclic aromatic hydrocarbons (PAHs) in different seasons from Shanghai, China

PM_2.5 samples in four representative periods were collected from a highly industrialized district in Shanghai, China. The concentrations of PM_2.5 and PM_2.5-bound PAHs were analyzed. Positive matrix factorization (PMF) model was used to identify the potential sources. Relationship between PAHs distribution and meteorological parameters was assessed meanwhile. The incremental lifetime cancer risks (ILCRs) model was applied to quantitatively evaluate the exposure risk of PAHs. Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLT) model was used to track the potential pollution area of PM_2.5 along with a Potential Source Contribution Function (PSCF) and Concentration Weighted Trajectory (CWT) methods. The results showed concentrations of PM_2.5 and PAHs ranged from 14.83 to 185.58 μg/m³, 2.58 to 123.62 ng/m³, respectively. The source apportionment model indicated that traffic emissions were the most important sources in each sampling season, which accounted for 38.44%, 34.48%, 39.04% and 45.03%, respectively. Spearman correlation coefficient showed that PAHs had negative correlation with ambient temperature and relative humidity in some periods, while had no significant correlation with atmospheric pressure and visibility. The average estimated lifetime cancer risk for total PAHs reached 4.7 × 10^-5, 4.5 × 10^-5 and 4.1 × 10^-5, 4.0 × 10^-5 to exposed children and adults in winter and autumn, respectively, meaning that PM_2.5-bound PAHs had high potential risk. HYSPLIT model suggested that monsoon greatly influenced the air quality in both winter and autumn.