| Based on the precipitation monitoring results in Nanjing City from 1991 to 2013,the variation of acid rain and the changing trend of ion composition and ion concentration were analyzed through Spearman correlation coefficient.The results showed that since 1991,the frequency of acid precipitation has been rising and the pH value shows marked drop in precipitation,which indicates that the acid rain pollution is on the rise.The main factor of acid precipitation is still sulfur oxides in Nanjing City,but its action on acid rain is decreasing year by year while the action of NO-3 is rising.Pollution of precipitation caused by chlorides,which come from the chemical industry,is improved.The neutralization effect of calcium,which comes from alkaline particulate matter,is weakened year by year. |
