北京市近二十年(1987～2004)湿沉降特征变化趋势分析

通过分析降水酸度和沉降量2个酸沉降控制指标,得出北京市近二十年(1987～2004)湿沉降特征变化趋势.研究发现,1998年以后北京市的湿沉降污染有严重的趋势.pH值逐年下降至5.52,酸雨频率逐年上升.湿沉降中的硫组分来自北京本地污染源排放的SO2和远距离输送.含氮组分对湿沉降的贡献作用明显增加.钙沉降是湿沉降中变化最大的因素,钙沉降量明显下降.1998年以后所采取的使总悬浮颗粒物浓度大幅下降的污染控制措施,可能直接导致了湿沉降酸化的加剧.酸沉降污染控制是一个复杂的控制过程,不能单纯地依靠控制本地的SO2排放量,北京市SO2排放量虽然得到了削减,但是湿沉降污染并未减缓.

Trend analysis of wet deposition between 1987 ～ 2004 in Beijing City

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.