Effect of coagulation on the asymmetric charging of aerosols

The asymmetric charge distribution on submicron aerosols has been examined by solving the ion–aerosol balance equations including the effects of both the ion–aerosol attachment mechanism and the coagulation of charged aerosols. Our results for the case of asymmetric charging show a decrease in the charging asymmetry as compared to Hoppel and Frickʹs [Aerosol Sci. Technol. 5 (1986) 1] results where the effect of coagulation is not included. Further, the results show an excess of negative aerosols when the number of elementary charges on the aerosols p≤3 and an excess of positive aerosols when p≥4. As in the case of symmetric charging, in asymmetric charging, the particle charge distribution is found to depend on the aerosol concentration and the rate of ionization. The contribution of the coagulation process becomes significant when the aerosol concentration exceeds ∼105 particles cm−3. Moreover, the charging asymmetry increases with increasing aerosol concentrations but decreases with the increasing ionization rate.