中文摘要：

为了研究北京城市浓雾生成机理以及雾水的污染情况,2006年12月11—12日,在北京南郊北京市观象台（39°56′N、116°17′E）对水平能见度在100m以内的浓雾进行了观测,并分析了这次浓雾形成的天气条件,对所采集的雾水进行了离子组分分析。结果显示：这是一次平流辐射雾,雾层厚约150m,能见度小于100m;在高空槽前、稳定边界层中,近地面正相对涡度区内有气流辐合和暖湿平流,日落之后地面降温迅速,有利于雾的生成;地面偏南风配合近地层暖平流,有利于增加雾的浓度;浓雾的形成发展时段内伴随着大气五级重污染事件。与1999年北京的雾水采样比较：pH值上升,电导率下降,阴离子浓度普遍下降,阳离子浓度有所上升。研究表明,近年来北京城市所采取的治理措施,减轻了浓雾及其雾水中的污染。

英文摘要：

In order to study the formation mechanism of urban heavy fog and the pollution of fog-water,an observation of a heavy fog with the visibility of 100m during 11-12 Dec,2006 was made in Beijing Observatory located in the south suburb（39°56′N,116°17′E）.The synoptic system and fog-water ionic species concentration was analyzed in the work.The results demonstrated that the observed fog process was an advection-radiation fog with a deep layer of more than 150 meters and a low visibility of less than 100 meters.In the front of upper trough there exits a stable boundary layer,accompanying with convergence and warm moist advection in the surface positive relative vorticity area.The surface temperature decreased rapidly after sunset,which is favorable for the fog formation.The south-oriented wind and warm advection layer on the ground result in an increase of fog concentration.The formation and increase of heavy fog accompany with the air pollution index Ⅴ（APIⅤ） increasing.Compared with Beijing＇s fog-water sample of 1999,the pH rises,electric conductivity rate descents,the anion＇s concentration generally decreased and the cation concentration increased.Investigation shows that the pollution of heavy fog and fog-water of Beijing has been reduced through efficient control.