Description:
Polycyclic aromatic hydrocarbons (PAHs) and their nitrated derivatives (NPAHs) attract continuous attention due to their outstanding carcinogenicity and mutagenicity. To investigate the seasonal and diurnal variations, sources, formation mechanism and health risk assessment of PAHs and NPAHs, PM2.5 were collected at an urban site in Beijing from 2017 to 2018. The highest PAHs and NPAHs concentrations were 77.92±54.62 ng/m3 and 963.71±695.06 pg/m3 in winter, which were several times larger than those in other seasons. Distinct diurnal variations of nocturnal levels higher than daytime levels were shown for PAHs and NPAHs. Source analysis indicated that except vehicle exhaust, biomass burning in spring, coal and biomass combustion in fall and winter were also important sources of PAHs and NPAHs. Atmospheric reactions contributed to the secondary formation of NPAHs specially in spring and summer. NO2 and RH could positively influence the heterogeneous formation of NPAHs when RH < 60%. Quantum calculation results confirmed the formation pathway of 2N-FLA from the OH/NO3-initiated oxidation of FLA. The results of health risk assessment showed the potential health risks for the residents, especially in winter. These results indicated that persistent organic pollutants still deserve attention following with the decrease concentrations of particulate matter