Secondary aerosols formation and nucleation in foggy weather events

The formation, nucleation and impacts of the secondary aerosols of SO4, NO3 and NH4 originated from pollution gaseous precursors of SO2, NOx and NH3 in foggy weather events of Northern China are investigated by field observations and numerical simulation by WRF/Chem model coupled with anthropogenic emission inventory. Results show that the secondary aerosols of SO4, NO3 and NH4 had important impacts on the formation processes and microphysical structure of the foggy event. The concentrations of NOx and NO3 were found to be extremely high in these cases. The concentration of interstitial aerosol NO3 was much higher than SO4 and NH4, but the concentration of SO4 was highest in cloud-borne aerosols. The averaged nucleation activation ratios for SO4, NO3 and NH4 could be as high as 30%, and the maximum ratios could reach over 80% during the fog episode The polluted atmospheric boundary condition can create a favorable condition for fog formation, and increase the fog area by 50% and 5 times in intensity, and ...