2021年青岛市一次PM_(2.5)和沙尘混合空气污染过程分析

Analysis of a Mixed Air Pollution Process of PM_(2.5) and Dust in Qingdao in 2021

以2021年3月青岛市空气自动站监测数据为依据,借助环境气象激光雷达、气溶胶激光雷达、在线离子色谱仪等技术手段,并利用后向轨迹模式(HYSPLIT)对青岛市一次PM_(2.5)和沙尘混合空气污染过程、气象条件、颗粒物组成以及传输路径等进行了综合分析。结果表明:静小风、湿度大、垂直方向逆温以及高空多次向近地面的污染物输送是第1阶段PM_(2.5)污染的主要原因,NO^(-)_(3)、SO^(2-)_(4)、NH^(+)_(4)浓度分别占水溶性离子浓度总和的51.7%,24.8%,22.4%,三者之和占ρ(PM_(2.5))的52.3%,机动车源、工业源和燃烧源贡献较大,其中尤以机动车源影响最显著;第2阶段各子站颗粒物浓度变化呈现明显的传输特征,PM_(2.5)中Ca^(2+)浓度升至第1阶段的6倍,沙尘源影响显著,污染气团主要来自蒙古国和我国内蒙古,前期由西北地区直接到达青岛,后期是经渤海湾、烟台到达青岛东南海域,最后回流至青岛;冷高压强度较弱导致近地面水平扩散条件不利,ρ(PM_(10))长时间维持在较高水平。

Based on the monitoring data of Qingdao automatic air station in March 2021,with the help of environmental meteorological lidar,aerosol lidar and on-line ion chromatograph data,and using the backward trajectory model(HYSPLIT),a comprehensive analysis has made on the air pollution process,meteorological conditions,particle composition and transmission path of PM_(2.5) and sand dust mixture in Qingdao.The results showed that the main causes of PM_(2.5) pollution in the first stage were quiet wind,high humidity,vertical temperature inversion and multiple pollutant transportation from high altitude to the ground.The concentrations of NO^(-)_(3),SO^(2-)_(4) and NH^(+)_(4) accounted for 51.7%,24.8%and 22.4%of the total concentration of water-soluble ions respectively,and the sum of the three accounted for 52.3%of PM_(2.5) concentration.Motor vehicle sources,industrial sources and combustion sources contributed a lot.Among them,the influence of vehicle source was the most significant.In the second stage,the change of particle concentration in each sub station showed obvious transmission characteristics,the concentration of Ca^(2+)in PM_(2.5) increased to 6 times of that in the first stage,and the influence of dust sources was significant.The polluted air mass mainly came from Mongolia and Inner Mongolia.In the early stage,it directly arrived at Qingdao from Northwest China,and in the later stage,it reached southeast Qingdao via Bohai Bay and Yantai,and finally returned to Qingdao.The weak cold high pressure led to unfavorable horizontal diffusion conditions near the ground,and PM_(10) concentration remained at a high level for a long time.