中国青岛市近年来灰霾污染数值模拟研究

The Numerical Modeling of Recent Haze Pollution in Qingdao,China

基于SO_(2)和PM_(2.5)的小时观测数据,本研究发现青岛市2014—2018年采暖期间SO2和PM_(2.5)平均浓度呈现下降的趋势,但是高浓度PM_(2.5)在不同年份偏移明显,尤其是2015年高浓度PM_(2.5)显著高于其它年份。为阐明这一时期高浓度PM_(2.5)的物理化学过程,利用区域气象化学模式Weather Research and Forecasting-Community Multiscale Air Quality Model(WRF-CMAQ)对2015年12月~2016年1月的PM_(2.5)累积和清除的物理化学过程分析,发现浓度累积主要受源排放、气溶胶过程和垂直对流过程影响,清除的主要控制过程为垂向扩散和水平对流。同时,对2015年12月29~31日和2016年1月15~17日两次高浓度PM2.5污染事件的分析发现,PM_(2.5)的主要成分为二次无机离子(SNA)和有机气溶胶(OA),其中SNA占比44%,OA占近30%。SNA主要由气溶胶反应过程、垂直和水平对流过程控制,OA主要受垂直和水平对流过程影响。本研究揭示的影响PM2.5组分的不同物理化学过程,一方面利于污染减排政策更有针对性的制定;另一方面从模式开发的角度,改进PM_(2.5)高比例组分,如SNA和OA的模拟能力,对于PM_(2.5)生消的机制解析具有重要意义。

Based on the hourly monitoring data of SO_(2)and PM_(2.5)in Qingdao,this study illustrates a decreasing trend of SO_(2)and PM_(2.5)concentration during the heating period from 2014 to 2018 in Qingdao.However,the high concentration of PM_(2.5)shifted significantly in different years,especially in 2015,when the high PM_(2.5)concentration was significantly larger than the other years.In order to elucidate the physical and chemical processes governing the high PM_(2.5)concentration during this period,regional model Weather Research and Forecasting-Community Multiscale Air Quality Model(WRF-CMAQ)was used to elucidate the processes modulating the accumulation and removal of PM_(2.5)during December 2015 and January 2016.The analysis showed that the accumulation of PM_(2.5)was mainly contributed by emission,aerosol process and vertical advection,whereas the major removal processes included vertical diffusion and horizontal advection.Meanwhile,focusing on two episodic events during December 29 to 31,2015 and January 15 to 17,2016,we found that the main components of PM_(2.5)were secondary inorganic ions(SNA)and organic aerosol(OA),with SNA accounting for 44%and OA nearly 30%.SNA is mainly controlled by the aerosol process,vertical and horizontal advection,while OA is mainly influenced by vertical and horizontal advection.The elucidation of physical and chemical processes affecting the PM_(2.5)compositions,on the one hand,may help to foster a more appropriate air pollution control strategy;On the other hand,from the perspective of model development,improving the ability of the model in simulating the components with high portion such as SNA and OA is of great significance in understanding the mechanism responsible for the accumulation and removal of PM_(2.5).