Effect of Fog Process on the Size Distribution of Polycyclic Aromatic Hydrocarbons in the Atmospheric Aerosol PM10

Fractionating samples of atmospheric aerosol PM10, collected during a fog high frequency period, were determined for 16 priority polycyclic aromatic hydrocarbons(PAHs). Result shows that the average mass concentrations of PM2.1 and PM9.0 in the near surface layer of the fog area increase sufficiently, and the diurnal concentration variation of PM2.1 are changed due to fog process. Before, during and after fog event, the 16 priority PAHs in the PM10 mainly distribute in the fine particles with larger specific surface area, and averagely, 83.04% of PAHs distribute on the aerosol with D-p <2.1 mu m. During the fog event, the concentrations of Sigma 16PAHs in the particles(D-p = 1.1-2.1 mu m) increase remarkably, whereas those in the particles(D-p < 0.65 mu m) decrease slightly; therefore, fog process play a great role on the distributions of Sigma 16PAHs in the fine particles. In the daytime before, during and after fog event, the distributions of Sigma 16PAHs in the accumulation mode have large differences; the peak diameter of accumulation mode shifts to the larger size during the fog event, compared with those before and after fog. In a prolonged fog event, the peak diameter of day. time Sigma 16PAHs accumulation mode shifts to the larger size continuously and stays at 1.1-2.1 mu m, while there is no significant variation of peak diameter in the night, all at 1.1-2.1 mu m; subsiquently, the size distributions of Sigma 16PAHs in PM10 are greatly affected by the duration of the fog event.