Study On The Long-Term Trend And Spatio-Temporal Distribution Of Acid Rain Over China

Acid rain damages natural environment, agricultural production and human health etc., and has become a worldwide environmental problem. Since the economic booming starting at 1980's, China has been becoming the major part of East Asia acid rain region, which follows other two large acid rain areas in the world--Europe and North America. Based on former researches, we choose data sets including pH value, conductivity,rainfall and so on from 88 stations between 1992 and 2006, and checked each item of the data according to original materials, then analyzed and evaluated the quality of the data for each station with K-pH inequation. We corrected the data which don't fit this inequation and testified the correction case is logical. Then we analyzed and classified the data of each station with different statistic methods. Finally, we obtained long-term complete and reliable acid rain data sets. Based on the reliable data, we studied the characteristics of long-term trend and spatio-temporal distribution of aid rain over China. Then we analyzed chemical components of precipitation for 3 regional baseline stations (Longfengshan, Shangdianzi, Linan). Spatio-temporal distribution and seasonality in Chongqing area between 1997 and 2006 were analysed considering this area is a severe acid rain region in China.The results indicate that Beijing nearby region (except for Tianjin), Central China and Southeastern Coastal China have decreasing trend of pH value. The areas that have increasing trend of pH value are East China and Southwest (except for Chongqing). The areas that have increasing trend of conductivity are Northeast China, east of Northwest China, Southwest China, middle and lower reaches of Changjiang river and South China. Qinhuangdao, Guiyang and southwest of Chongqing area have decreasing trend of conductivity.The results of two interpolation methods are consistent in most areas except for western area that has fewer stations. The interpolation results are reliable and show that the south of Changjiang river is the most severe acid rain region, which agree with the results issued by Environmental Protection Agency. But there are still some differences between them because of the differences in station selection, monitoring procedure and interpolation methods. The areas with similar climate and rainfall conditions are similar in pH value, but still different in conductivities.In Northeast, North and East of china, the major anions are SO42- and NO3- and major cations are NH4+ and Ca2+. The concentration of SO42- is slightly higher than NO3- and the concentration of NH4+ is two times higher than Ca2+. Industrial emissions, agricultural activities and biomass burning contribute most to the precipitation chemistry in the 3 areas. Influence by sea salt is more significant in East China compared with other areas. The seasonality and spatial discrepancy of acidity and conductivity of precipitation are obvious over Chongqing area.