Characteristics and Source Identification of Polycyclic Aromatic Hydrocarbons and n-Alkanes in PM2.5 in Xiamen

PM2.5 samples were collected to characterize the organic compounds of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes in Xiamen, China, in 2013. The concentrations of PM2.5, PAHs and n-alkanes were 55.53 mu g m(-3) and 22.14 mu g m(-3), 15.73 +/- 6.25 ng m(-3) and 5.65 +/- 3.73 ng m(-3), and 148.57 +/- 36.84 ng m(-3) and 97.53 +/- 67.46 ng m(-3) in winter and summer, respectively, demonstrating higher pollutant levels in wintertime. Benzo[e] pyrene (BeP) was the most abundant PAH, accounting for 32% and 26% of the total quantified PAHs in winter and summer, respectively, followed by coronene (Cor) and phenanthrene (Phe). 5-ring PAHs were the most dominant group, contributing 50.8% and 44.1% to the total quantified PAHs in winter and summer, respectively. Two peaks were exhibited by the homologue distributions of n-alkanes, and the dominant components were enriched in the high molecular weight fraction. Meteorological parameters had a stronger impact on the atmospheric PAH levels in summer than winter, and the most significant parameter was relative humidity (RH), followed by temperature. The diagnostic ratios indicated that PAHs in Xiamen were mainly contributed by petroleum combustion in the two seasons and the concentrations of n-alkanes were mainly influenced by anthropogenic sources. The annual values of the benzo[ a] pyrene (BaP) equivalent concentration and incremental lifetime cancer risk (ILCR) were 0.83 +/- 0.63 ng m(-3) and 7.17 x 10(-5) in winter and 1.11 x 10(-4) ng m(-3) and 3.29 x 10(-5) in summer, respectively. The findings illustrated that the overall exposure risk to PM2.5-bound PAHs did not trigger an alert in Xiamen, but higher risks in winter were still shown to exist.