[Pollution Characteristics and Risk Assessment of Nitro Polycyclic Aromatic Hydrocarbons in PM_2.5 of Nanjing, China]

Nitro polycyclic aromatic hydrocarbons (NPAHs) are important pollutants with carcinogenic effects present in PM_2.5. To analyze the pollution characteristics and sources of NPAHs, 14 samples of PM_2.5 were collected in Nanjing from November 2017 to March 2018. The results showed that, 2,8-dinitrodibenzothiophene (743 pg·m^-3), 2, 7-dinitrofluorene (331 pg·m^-3), 9-nitroanthracene (326 pg·m^-3), 3-nitrofluoranthene (217 pg·m^-3), and 1,8-dinitropyrene (193 pg·m^-3) were dominant, and the detection concentrations notably varied between seasons; the highest concentrations occurred in winter (3082 pg·m^-3) followed by autumn (1553 pg·m^-3) and spring (1218 pg·m^-3). The ratio of nitrofluoranthene and 1-nitropyrene concentrations, and 9-nitroanthracene and 1-nitropyrene concentrations, indicated that the main sources of NPAHs in the PM_2.5 of Nanjing were photooxidation of polycyclic aromatic hydrocarbons and biomass burning. NPAHs were more typically associated with smaller particles, which further indicated that secondary formation is an important source. The current carcinogenic risk of NPAHs in PM_2.5 in Nanjing is controllable, and dinitro-polycyclic aromatic hydrocarbons represent the highest level of risk. The data presented in this study provide important baseline information that can inform the management of risks associated with NPAHs in PM_2.5 in Nanjing.