奥运会及残奥会期间北京市区大气颗粒物污染特征及微观形貌类型

2008年8月和9月,北京市成功举办了第29届奥运会和第13届残奥会,对这段时间在北京市区(中国矿业大学校园综合楼五层,距奥运村3 km)采集的大气颗粒物的质量浓度和微观形貌类型进行了研究。结果表明:奥运会期间,北京市区大气PM10和PM2.5的日均质量浓度分别小于国家PM10二级标准(150μg/m3)和美国EPA的PM2.5二级标准(65μg/m3),12 h的质量浓度范围分别为7.64~81.63μg/m3和1.91~54.59μg/m3;残奥会期间,12 h的PM10质量浓度范围为33.83~106.36μg/m3,没有超标,PM2.5质量浓度变化范围为15.29~88.30μg/m3,其中出现了3 d超标天,分别为9月6日、7日和14日;从奥运期间PM2.5/PM10的比值(0.26~0.86,大部分值大于0.5)可以看出,奥运期间北京大气颗粒物以细粒子为主。与往年相比,颗粒物质量浓度出现大幅下降趋势。场发射扫描电镜观察显示,奥运会和残奥会期间样品的微观形貌类型主要有球形颗粒、烟尘集合体、不规则矿物和未知颗粒,其数量-粒径分布主要呈单峰分布,峰值均在0.1~0.2μm范围,其中球形颗粒明显占多数。各种分析数据均显示,残奥会期间样品比奥运会期间样品污染要严重。

Characteristics of Pollution and Microscopic Morphology of Atmospheric Particulate Matter in Beijing during 2008 Olympics and Paralympics

In August and September of 2008 Beijing held the 29th Olympics and 13th Paralympics successfully.The atmospheric particulate matter was collected during this period on the campus of China University of Mining & Technology(Beijing) which is about 3 kilometers from central Olympic Stadium.The mass concentrations and morphological types of the airborne particles were investigated.The results showed that the mass concentrations of PM10 and PM2.5 during the Olympics were well below the national standard II(150 μg/m3) and USA-EPA daily mean standard(65 μg/m3),respectively,with the 12-hour means ranging between 7.64 μg/m3 and 81.63 μg/m3 for PM10 and between 1.91 μg/m3 and 54.59 μg/m3 for PM2.5.The 12-hour concentrations of PM10 during Paralympics ranged between 33.83 μg/m3 and 106.36 μg/m3,which are higher than those during the Olympics but are still lower than the national standard II.Mass concentrations of PM2.5 during the Paralympics samples ranged between 15.29 μg/m3 and 88.30 μg/m3,and the PM2.5 levels during most days of Paralympics were relatively low,except 6th,7th and 14th of September when the PM2.5 level exceeded USA-EPA daily mean standard.The PM2.5/PM10 ratios during the Olympics and Paralympics were in the range between 0.26 and 0.86,mostly higher than 0.5,demonstrating a predominance of the PM2.5 in PM10.Compared with previous years,mass concentration of PM2.5 and PM10 are both in a decreasing trend.The microscopic morphologies and size distribution of particle samples were further examined by FESEM and Image Analysis.Spherical particulate,soot,irregular minerals and unknown fine particles were identified.The number-size distribution of these samples showed that the particles are mainly concentrated in the size range of 0.1-0.2 μm,in which the spherical particles are dominated.All data indicated that the pollution of the airborne particles in Beijing city during the Paralympics is more severe than that during the Olympics.