A study on rain acidification processes in ten cities of China

A physico-chemical sub-cloud rain acidification model is used to simulate t he acidification processes of rainwater in ten cities of China, based on th e observation data of the chemical components of cloud- and rainwater and t he concentrations of gaseous and aerosol species. The results show that the re are in-cloud process and below-cloud process in the formation of acid ra in, but the relative importance of these two processes is different in vari ous cities. The acidification of rainwater under cloud is very important in Guiyang, Shanghai, Jilin, Beijing Changsha and Chongqing, and the in-cloud and below-cloud process contribute, equally to the acidification in Guilin , however, the acidification of rainwater in cloud is more important in Nan chang and Guancrzhou. Overall, the aerosol has an alkalization effect on th e rain, about 11%-25% of H+ concentration in the rainwater is neutralized o ver Southern China and 60%-70% is neutralied over Nor-them China by aerosol species. The effect of atmospheric SO2 on acidification of rainwater is no nlinear and is different in various regions. The effects of the variation o f atmospheric NH3, H2O2 and aerosol species on pH of rainwater are also dis cussed in detail.