MECHANISM OF AQUEOUS OXIDATION OF S(IV) FOR BELOW-CLOUD SCAVENGING TRACE GASES
Shen Ji, Zhao Qianxue, Zhao Dianwu (Research Center for Eco-Environmental Sciences, Academia Sinica Beijing)
The mechanism of aqueous oxidation of S(IV)for below-cloud scavenging trace gases has been simulated numerically, four oxidation pathways considered were, by O3, by H2O2, by Mn~(2+), Fe~(3+) catalytically and oxidation after the rain reached on the ground. The effects of the concentrations of gaseous SO2, NH3, the acidity of the precipitation, the rain drop size and the duration of the precipitation on the production of SO4~(2-) were also studied. It was demonstrated that in North China, all pathways are important with the one by O3 to be the most. In South-west China, the pathway by O3 plays an important role until pH drops to about 4.6, with further acidification of precipitation, the one by H2O2 becomes to be dominant.