Seasonal variations of NPAHs and OPAHs in PM 2.5 at heavily polluted urban and suburban sites in North China: Concentrations, molecular compositions, cancer risk assessments and sources.

16 nitrated polycyclic aromatic hydrocarbons (NPAHs) and 5 oxygenated polycyclic aromatic hydrocarbons (OPAHs) in PM2.5 at two locations in Northern China were analyzed by Gas Chromatography-Mass Spectrometry (GC-MS). Sampling was conducted at an urban site in Shandong University in Jinan (SDU) and a suburban site in Qixingtai in Jinan (QXT) in March, June, September and December in 2016. Overall, the concentrations of NPAHs and OPAHs were higher at SDU (1.88 and 9.49 ng/m3 , respectively) than QXT (1.57 and 6.90 ng/m3 , respectively), and the NPAHs and OPAHs concentrations were significantly higher during the winter than the other seasons at both sites. The incremental lifetime cancer risk (ILCR) values were lower than 10-6 for all sites, seasons and age groups (ranging between 1.85E-08 and 2.56E-07), so there was no risk of carcinogenesis due to exposure to these pollutants. Total cancer risk at SDU was higher than QXT and NPAHs have the highest carcinogenic risk for adults aged from 30 to 70 years. The positive matrix factorization (PMF) results revealed that coal/biomass combustion, diesel vehicle emissions, gasoline vehicle emissions and secondary formation were the main sources of NPAHs and OPAHs at SDU and QXT. Coal/biomass combustion contributed more in spring, autumn and winter; diesel vehicle emission contributed the most in summer; secondary formation made greatest contributions in winter; the contributions of gasoline vehicle emission were similar in summer, autumn and winter. Diagnostic ratios clearly demonstrated that secondary formation is more active in winter than in other seasons, and the reactions of PAHs and OH radical were the dominant secondary formation pathway at both SDU and QXT. In addition, the potential source contribution function (PSCF) identified that the Beijing-Tianjin-Hebei region, Shandong province, Bohai Sea, Yellow Sea, Anhui province and Henan province were the main source regions of NPAHs and OPAHs in Jinan.