EFFECT OF OXIDATION ON ACIDIFICATION OF CLOUD DROPLET IN CONDENSATIONAL GROWTH

In order to investigate the effect of the drop-phase oxidation due to rainout (in cloud scavenging) of gaseous air pollutants on the acidification of cloud droplets, the characteristics of the acidification of a growing cloud droplet by the rainout of SO2 (g) are simulated numerically with use of a mathematical model based on physicochemical consideration.(NH4) 2SO4is selected for the cloud condensation nucleus (CCN), which is a major aerosol and produced from NH3 (g) and SO2 (g) via gas-phase chemical reaction in the atmosphere. With use of the model the droplet radius and the concentrations of chemicals are simulated. It is shown that with lapse of time the hydrogen ion concentration continues to increase beyond the equilibrium concentration (obtained in the case without the oxidation) and that a plateau appears in the concentration profile.