广州市春季一次沙尘天气过程综合观测

2017年4月21—23日广州市经历了一次远距离传输的沙尘天气过程,为了解沙尘过程对广州市空气质量的影响,基于广州市大气超级站,利用单颗粒气溶胶质谱(SPAMS)、气溶胶激光雷达观测数据并结合HYSPLIT后向轨迹模型分析了沙尘过程细颗粒物组分及污染来源贡献变化和沙尘气溶胶的来源及路径。结果表明:受沙尘过境影响,PM_(10)浓度大幅升高,PM_(2.5)/PM_(10)最小值仅为12.1%;沙尘过境期间影响近地面颗粒物的沙尘高度主要分布在1 km以下区域,近地面颗粒物消光系数均值为100.11 Mm~(-1),探测到最大退偏振比为0.28。SPAMS研究发现沙尘过境期间含硅酸盐颗粒物(SI)的细颗粒物数浓度比例达25.9%,是沙尘过境前的1.4倍;PM_(2.5)中扬尘贡献率明显增大,达到了17.3%,是沙尘过境前的1.9倍。后向轨迹模型HYSPLIT显示此次沙尘为典型的北方沙尘传输,沙尘源自中国西北地区,传输方向为自西北输送至华东地区后,转为东南方向影响广州市。

Observation Studies on a Dust Case in the Spring of Guangzhou

A dust case had occurred in Guangzhou in 21^st-23^rd, Apr 2017. In order to understand its effect to the air quality of Guangzhou, the chemical composition, source apportionment of fine particle along with the source and tracks of dust aerosol were analyzed by aerosol Lidar, single particle aerosol mass(SPAMS)and air mass backward trajectory model at the Guangzhou Atmospheric Supersite. The results indicated as follows: Influenced by dust, the concentration of PM₁₀ increased significantly and the minimum value of PM_2.5/PM₁₀ was only 12.1%.Then the dust aerosol which influenced the concentration of PM₁₀ mainly distributed below 1 km region. In addition, the average value of particle extinction coefficient was 100.11 Mm^-1 and the maximum of depolarization ratio reached to 0.28. Besides, SPAMS system results indicated that the proportion of SI type particle in atmosphere was 25.9%, 1.4 times of that before the dust crossing. While the contribution of dust to PM_2.5 increased significantly during the dust process, whose proportion was 17.3%, 1.9 times of that before the dust crossing. Finally the result of the air mass backward trajectory model of HYSPLIT showed that this dust process was a typical north dust transmission, and the dust was came from the northwest of China, while transmission direction was from northwest transport to the east region of China, then turned into southeast direction and affected Guangzhou.