中文摘要：

本地排放和区域传输共同影响着北京及周边地区的空气质量．2007年8月在北京清华大学、密云水库、河北任丘和内蒙古商都采集颗粒物样品并获得了PM2.5质量浓度和TSP中22种无机元素的时空分布特征．4个观测点PM2.5，质量浓度高低顺序为任丘〉清华〉密云〉商都．二次污染元素S和一次污染元素Zn、Pb、Cu、As、Sb、Ni、Cd、In、Se在任丘的PM中含量最高，表明该观测点受人为源影响最为显著，其较弱的日变化幅度表明高浓度PM主要由本地源贡献；商都地区污染元素浓度随时间变化波动最为剧烈，受气象条件导致的传输影响较大；清华和密云的S、Pb、Cd、In、As、Zn的相关系数均大于0．70，其来源具有一定相似性；在锯齿型污染过程的开始和结束，密云各元素浓度值达到和区域背景点商都观测期间最低值相近的水平，表明密云可以表征西北洁净空气的区域特征；PM峰值阶段，整个地区高浓度硫酸盐的均匀分布（约10μg／m^3）证实了锯齿型区域污染的二次性本质．结合元素富集因子的不同分布特征讨论了各地区PM的可能来源及相互影响．

英文摘要：

The air quality in Beijing and surrounding area is influenced by local emission and regional transport. To study the characteristics of regional pollution, PM （particulate matter） samples were collected simultaneously at 4 sites including Tsinghua University （TH） and Miyun reservoir （MY） in Beijing, Renqiu （RQ, Hebei Province）, and Shangdu （SD, Inner Mongolia） during August, 2007, and temporal/spatial distributions of PM2.5 mass concentrations along with 22 elements in TSP were characterized. PM2.5 mass concentrations were quite different at 4 sites, following the sequence as RQ 〉 TH 〉 MY 〉 SD. The highest concentrations of pollution-derived elements S, Zn, Pb, Cu, As, Sb, Ni, Cd, In, Se were found in RQ, showing the most intensive anthropogenic influence around this region, and their lowest variation indicated that the pollution mostly came from local sources. Controlled by the meteorological factors, highest daily variations of these elements were found at SD with relative lower concentrations. The correlation coefficients of S、Pb、Cd、In、As、Zn concentrations between TH and MY were all higher than 0.70, which implies similar sources for these elements at the 2 sites in Beijing. At the beginning and the end of the Sawtooth pollution episode in Beijing, concentrations of most elements in Miyun were comparable with the lowest concentrations at Shangdu observed during the sampling period, which means Miyun could well represent the regional characteristics of clean air mass from the northwest. Uniform spatial distribution of high sulfate was found（about 10 μg/m^3） at the peaks of Sawtooth episode, which implies the important contribution from secondary aerosol during the regional pollution. Variable sources of PM at each site and their regional influence were discussed based on the different characteristics of elemental enrichment factors.