Characterization of PM2.5-Bound Polycyclic Aromatic Hydrocarbons at Two Central China Cities: Seasonal Variation, Sources, and Health Risk Assessment

In this study, ambient PM2.5 samples were collected from October 2014 to August 2015 in urban area of Luoyang (LY) and Pingdingshan (PDS), two medium-size industrial cities in central China. Sixteen priority polycyclic aromatic hydrocarbons (PAHs) were analyzed to investigate the seasonal variation, potential pollution sources, and health risk of PAHs bound to PM2.5 (PM2.5-bound PAHs). The diagnostic ratios analysis and positive matrix fraction (PMF) model were used to identify potential sources of PM2.5-bound PAHs. The annual average concentrations of PM2.5 and PM2.5-bound PAHs were 128 μg m−3 and 73 ng m−3 for LY, and 119 μg m−3 and 182 ng m−3 for PDS, respectively, both displaying seasonal trends with higher concentrations in winter and autumn than in spring and summer. BaP equivalent concentrations were 14.4 and 16.5 ng m−3 in LY and PDS, respectively. The predominant PAHs were 4–6 ring PAHs, with contribution of more than 80% at both sampling sites. PMF analysis revealed that coal combustion was the most important source of PM2.5-bound PAHs in LY and PDS, accounting for 37% and 39%, respectively, followed by traffic emissions (34% and 33% in LY and PDS, respectively). The average inhalation cancer risk (ICR) for a lifetime of 70 years were 12.5 × 10−4 and 14.3 × 10−4 in LY and PDS, respectively, which were much higher than US EPA guideline limit of 10−6. The traffic source and coal combustion source contributed the highest ICR values in LY and PDS, respectively.