青岛市PM_(2.5)重污染天气演变过程分析

Analysis on the evolution of PM_(2.5) heavy air pollution process in Qingdao

运用WRF-CMAQ模式对2016年1月1日~1月7日青岛市的PM_(2.5)重污染天气进行了模拟研究,分析了青岛市PM_(2.5)重污染形成、持续和清除过程的主要影响因素.与观测对比表明,模式能够较好地模拟出青岛市主要气象要素和近地面PM_(2.5)浓度的变化特征.在重污染形成期,持续的西南气流将山东南部、安徽、江苏等地PM_(2.5)及其前体物传输至青岛地区;逆温层的出现及大气边界层高度的降低使得输送至青岛地区的PM_(2.5)在近地面积累,浓度升高.由山东西南部、安徽北部、河南东部等地传输至山东西北部和京津冀地区的PM_(2.5)及其前体物,在重污染持续期沿近地面传输至青岛,加之液相化学过程生成了大量的二次气溶胶,导致PM_(2.5)浓度一直维持在200μg/m^3以上.重污染清除期,风速加大,水平传输作用加强,高浓度的PM_(2.5)污染带向下风向转移.区域传输对此次青岛市PM_(2.5)重污染事件具有重要贡献,3个时期的贡献率分别为87.0%、68.5%和57.6%.

WRF-CMAQ model was used to simulate a severe PM（2.5） pollution episode in Qingdao from 1 to 7 January, 2016, and the major factors influencing the formation, persistence and removal of the severe PM（2.5） pollution were analyzed. The model reasonably reproduced the temporal and spatial variation of PM（2.5） concentration and meteorological conditions. Under the influence of persistent southwest airflow during the severe pollution formation period, PM（2.5） and its precursors were transported to Qingdao from the South of Shandong, Anhui and Jiangsu province. These pollutants continued to accumulate in Qingdao due to the favorable meteorological conditions such as the occurrence of inversion layer and reduced planetary boundary layer height. PM（2.5） and its precursors transported to Qingdao area from the Beijing-Tianjin-Hebei region and the Northwestern Shandong during the severe pollution persistence period, which originated from the Southwestern Shandong, north of Anhui and east of Henan province. In addition, numerous secondary aerosols were formed during the aqueous phase chemistry process, leading to persistently high PM（2.5） concentration of more than 200μg/m^3. During the severe pollution removal period, the wind speed was increased and thus enhancing the horizontal transport, the PM（2.5） was transported to the downwind areas. Regional transport was a major contributor to the severe PM（2.5） pollution, accounting for 87.0%, 68.5% and 57.6% during the three periods, respectively.