云下降雨洗脱痕量气体时S(IV)的液相氧化过程

用数值模拟跟踪S(Ⅳ)氧化生成SO_4~2的行为,研究SO_2及NH_3等气体浓度、降雨酸度、雨滴大小、持续降雨时间等因素对四个氧化途径(O_3氧化,H_2O_2酸催化氧化;Mn~(2+),Fe~(3+)催化氧化;降落到地面后S(Ⅳ)的氧化)的影响。 计算结果表明,我国北方地区云下降雨洗脱SO_2等痕量气体时,降雨中四个氧化途径都起作用,而以O_3氧化过程为主,在西南地区,首先是O_3氧化S(Ⅳ)起主要作用,而降雨的进一步酸化则是H_2O_2酸催化氧化S(Ⅳ),降雨过程中Mn~(2+),Fe~(3+)催化氧化S(Ⅳ)不是最主要途径。

MECHANISM OF AQUEOUS OXIDATION OF S(IV) FOR BELOW-CLOUD SCAVENGING TRACE GASES

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.