Trend analysis of wet deposition between 1987 ～ 2004 in Beijing City
北京市近二十年(1987～2004)湿沉降特征变化趋势分析

The trend of the wet deposition between 1987 and 2004 in Beijing city was analyzed by using two parameters, e.g. precipitation acidity and wet deposition fluxes. Since 1998 the value of pH has declined to 5.52, and acidification frequency has increased. The sulphate, among wet deposition of major species, came from local sources of SO_2 as well as long-range transportation. And nitrate showed increasing contribution to wet deposition. Meanwhile, wet deposition of calcium declined dramatically, probably due to stringent abatement efforts of total suspended particulates. The acid deposition in Beijing caused by not only local SO_2 emissions, but also regional SO_2 sources, Comparing the SO_2 sources, the monitoring results indicated that the wet deposition has been getting more severe in Beijing city recently.