2020年秋季济南市一次沙尘天气污染特征研究

Characteristics of a dust weather pollution in Ji'nan during autumn in of a dust weather pollution in Ji'nan during autumn in 2020

利用激光雷达观测资料、PM_(2.5)化学组分在线监测数据,结合常规污染物监测数据以及HYSPLIT模式结果,对济南地区在2020年秋季遭遇的一次沙尘天气过程进行分析。结果表明:①2020年10月21日10时沙尘开始影响济南市,PM_(10)小时浓度呈逐渐上升的变化趋势;15时,济南市PM_(10)小时浓度达到峰值(349μg/m^(3))。根据中国环境监测总站《关于沙尘天气过程影响扣除有关问题的通知》(总站气字〔2020〕76号)中关于沙尘天气影响起始和结束时间的确定方法,2020年10月21日13时至10月22日19时作为沙尘污染期间。②受高空槽和地面冷锋过境影响,上游沙尘以西北路径传输至济南地区。③沙尘期间,近地面至高空2.5 km退偏比值迅速上升,气溶胶非球形特征明显增强,颗粒物以粗粒子污染为主。④污染期间OC是PM_(2.5)中主要的碳质气溶胶,OC与EC相关系数为0.53,表明二者来自相同的污染源。⑤沙尘过境前,济南市PM_(2.5)中水溶性离子以NH_(4)^(+)、SO_(4)^(2-)和NO_(3)^(-)为主,体现了大量气态污染物的二次化学转化贡献更为明显;沙尘影响期间,NH_(4)^(+)、SO_(4)^(2-)和NO_(3)^(-)明显下降,而Mg^(2+)、Ca^(2+)则迅速上升,其浓度分别较上一个小时上升37.2%和10.5%,矿物离子明显增长,一次源影响显著。

Using lidar observation data,online monitoring data of PM_(2.5)chemical components,combined with conventional pollutant monitoring data and the results of the HYSPLIT model,an analysis of the sand and dust weather process encountered in Jinan in the autumn of 2020 was carried out.the result showed:①At 10:00 on October 21,2020,sand and dust began to affect Jinan City,and the concentration of PM_(10)showed a gradually increasing trend.At 15:00,the concentration of PM_(10)in Jinan City reached its peak(349μg/m^(3)).According to the method of determining the start and end time of the impact of sand and dust weather,the period of sand and dust pollution is from 13:00 on October 21 to 19:00 on October 22,2020.②Affected by the transit of high-altitude troughs and ground cold fronts,the upstream sand and dust were transmitted to the Jinan area through the northwest route.③During the sand and dust,the depolarization ratio of the near ground under 2.5km rised rapidly,and the non-spherical characteristics of aerosols are significantly enhanced.④During the pollution period,OC was the main carbonaceous aerosol in PM_(2.5),and the correlation coefficient between OC and EC was 0.53,indicating that the two come from the same pollution source.⑤Before the sand and dust cross the border,the water-soluble ions in the PM_(2.5)were mainly NH_(4)^(+),SO_(4)^(2-)and NO_(3)^(-),which reflected the significant contribution of the secondary chemical conversion of a large number of gaseous pollutants.During the impact of sand and dust,NH4+,SO_(4)^(2-)and NO_(3)^(-)decreased significantly,while Mg^(2+)and Ca^(2+)rosed rapidly,and their concentrations increased by 37.2%and 10.5%respectively from the previous hour.Mineral ions increased significantly,and the primary source had a significant impact.