结合常规污染物监测、PM2.5化学组分监测、激光雷达监测和颗粒物数浓度及粒径监测等手段,对2017年5月影响北京市的一次沙尘天气过程进行分析.结果表明:5月4日凌晨起沙尘天气开始影响北京市,延庆、官园和通州3个站点PM10峰值浓度分别为2 091、2 245、2 590 μg/m3,体现了该次沙尘天气影响程度之重.PM2.5浓度与PM10变化一致,也达到重度污染的水平.沙尘天气移动路径是沿着区域西北至东南方向.沙尘天气主体从3 km左右的高空进入北京市,随后逐渐渗透至1 km高度以及地面,且沙尘层厚度较高,覆盖了地面至3 km的高度.沙尘天气过程中OM和Ca2组分增幅最大.在沙尘天气影响严重时间段,沙尘天气源与生物质燃烧源比例之和大于50％,最高值为67.6％.沙尘天气过程中颗粒物峰值粒径为0.965 ～1.037 μm.%A dust pollution episode in May,2017 was analyzed using regular pollutants observation,PM2.5 chemical composition observation,lidar observation,number concentrations of particulate matter observation and size spectrum observation.The results showed that the dust reached Beijing at early morning on May 4.The peaks of PM10 concentrations in Yanqing,Guanyuan and Tongzhou reached 2 091,2 245,and 2 590 μg/m3,respectively.The variation of PM2.5 concentration in this episode was consistent with that of PM10.The spatial analysis showed that the dust movement path was along the northwest to southeast of the region.Liar observation showed that the dust reached Beijing in the height of 3km,and then went down to the height of 1km and the ground.The dust layer was thick and covered the height of 0-3 km.The concentration increase of OM and Ca2 + were the highest during the chemical compositions of PM2.5.Online source analysis showed that the contribution of dust and biomass burning accounted for more than 50％ of the emission sources,with the highest contribution of 67.6％.The peak size spectrum of the dust was among 0.965-1.037 μm.
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