Characteristics Of Polycyclic Aromatic Hydrocarbons (PAHs) In PM₁₀ And PM_2.5 And The Influence Of Foggy Weather Conditions During The Winter In Nanjing

To study the distribution characteristics of polycyclic aromatic hydrocarbons (PAHs) in PM10 and PM2.5 and the influence of foggy weather conditions, aerosol samples were collected in foggy and sunny days in Nanjing,and the concentrations of 16 priority-controlled PAHs were analyzed by gas chromatography with mass selective detection (GC-MS).The results suggest that the total concentrations of 16 PAHs in PM10 and PM2.5 during foggy days are higher by 34.72 ng.m"3 and 35.35 ng.m^-3 respectively than those during sunny days. However, the diurnal variation in foggy days isn't exhibited, compared to sunny days. The proportion of low-ring PAHs in corresponding size ranges gradually decrease,while the high-ring PAHs gradually increase. In foggy day, the concentration of Bap related to the other homologous compounds and E PAHs well, indicating that they may come from the same sources; The main sources of atmospheric PAHs in TSP were estimated by ratios method, the result is that the main pollution sources were vehicle emission, coal combustion; Benzo(a) pyrene(BaP)-equivalent carcinogenic concentration (BaPE) in foggy days was higher by 1.48 ng.m^-3 than the regional standard (BaP, 5ng.m^-3). The analysis of meteorological conditions in foggy days shows that foggy days are characterized by the stable inversion layer and high relative humidity. Furthermore,the mass concentrations of 16 PAHs in particles in the range of 0.65μm to 2.1μm are gradually increases,exhibiting enrichment of accumulation mode. The existence of warm and moisture from southeast and southwest provides a rich source of water vapor and polluted particles which may act as fog condensation nuclei for fog, and at the same time, weak wind conditions are also proper for upper and lower air exchanging, resulting in a thicker fog, maintaining the development of fog, leading to significant increase of the PAHs pollution. To clear up organic pollutants such as polycyclic aromatic hydrocarbons in the air, precipitation (rain, snow, hail, etc.) is an effective way to remove pollution; The duration of fog had a significant effect on the polycyclic aromatic hydrocarbons in aerosols, in which particle size is 1.1-2.1μm.