SYNOPTIC SITUATIONS OF PM2.5 POLLUTION EPISODES AND TRANSPORTATION CHARACTERISTICS DURING A TYPICAL WINTER SEVERE POLLUTION EVENT IN ZHAOQING

WU Luo-lin; ZHOU Liu-yi; WANG Xue-mei; CHEN Wei-hua; DAI Jia-ning; SHA Chen-yuan; CHANG Ming

doi:10.16032/j.issn.1004-4965.2017.05.021

Abstract：In order to investigate the occurrence and development of severe particle pollution process,two-years (2013-2014) of continuous observation data of PM2.5 collected in Zhaoqing,Guangdong province were used and analyzed in this study to explore the seasonal variation of air quality and PM2.5 pollution processes.In addition,all the particle pollution processes,combined with their weather condition during 2013 and 2014,were summarized and analyzed,and the air quality numerical model (WRF-Chem) was applied to simulate and study a typical winter heavy haze event.The result showed that,a total of 27 pollution episodes were found in 2013 and 2014,and extreme pollution episodes mainly occurred in autumn and winter season.By analyzing the characteristics of PM2.5 pollution episodes,four typical weather conditions related to pollution episodes were summarized,including weak-high-pressure type (48％),tropical-depression type (22％),front type (19％) and strong-high-pressure type (11％).The prevailing wind direction was southeast and south under the influence of these weather conditions,and the atmosphere was in a steady state,resulting in the accumulation of pollutants and further leading to the occurrence of pollution episodes.Model results revealed that the adverse meteorological conditions and local emission sources were the key reasons for the occurrence of pollution processes.A four-dimensional flux model was employed to study the regional transport flux of atmospheric pollutants.Negative net flux was found for PM2.5,indicating that the pollutants in Zhaoqing area were exported to adjacent areas,especially NO3-and NH4+,which showed a relatively high negative flux.In addition,the transport pathway of pollutants in Zhaoqing mainly ran from southeast to northwest.The nonlocal pollutants tend to be transported through the pathway and further influence the air quality of Zhaoqing area.