中文摘要：

为研究大气污染物在近地层内的垂直分布规律,2009年2月10—25日利用被动采样器在北京325 m气象铁塔10个高度（8、15、47、80、120、160、200、240、280、320 m）对SO_2、NO_2、O_3、NH_3和苯系物（苯benzene、甲苯toluene、乙苯ethylbenzene和二甲苯xylene）共8种大气污染物浓度进行了同步观测.结果表明,北京城区冬季污染物浓度具有明显的垂直变化特征,污染物浓度从近地面开始逐渐上升,在80—160 m以内的某一高度到达峰值后逐渐下降;200—300 m范围内,大气污染物浓度的垂直变化幅度相对较小,浓度值与地面接近;200 m以下各种污染物浓度的变化比较剧烈,浓度极大值出现的高度有所不同,O_3、SO_2和NH_3极大值位于160 m,苯和NO_2极大值出现在120 m,甲苯、乙苯和二甲苯极大值在80 m处.污染物在不同高度富集可能与污染源排放高度、城市冠层的热动力作用和气象因素有关,区分这些因素的各自贡献尚需进一步研究.

英文摘要：

To examine the vertical distribution of air pollutants in the lower atmospheric boundary layer,the concentrations of SO_2,NO_2,O_3,NH_3 and BTEX（ benzene,toluene,ethylbenzene and xylene） were measured simultaneously by passive samplers on a 325 m meteorological tower at ten heights（ 8,15,47,80,120,160,200,240,280 and 320 m）,during February 10—25,2009 in urbanBeijing. The results show that the highest concentration of aforementioned air pollutants along the vertical profile was always observed at 80—160 m height,decreasing toward the surface and toward higher altitudes. The concentrations of these pollutants between 200—300 m varied insignificantly,with values close to those at the surface. In contrast,the concentrations of these pollutants changed dramatically below 200 m,with the maximum values at 160 m for O_3,SO_2 and NH_3; at 120 m for benzene and NO_2; and at 80 m for toluene,ethylbenzene and xylene. The elevated concentrations of gaseous pollutants coincided with the inversion layer and were likely influenced by the emission heights of point sources and the meteorological conditions,as well as the dynamic and thermal effects of urban canopy combined. The individual contribution of these factors needs to be separated in future work.