长三角地区2015年大气重污染特征及其影响因素

We analyzed ground air quality measurements from 129 monitoring stations in the Yangtze River Delta (YRD) region during 2015 to examine the spatial and temporal variabilities of severe air pollution episodes in this region. By using the meteorological information and backward trajectory model, we investigated the effects of meteorological factors and regional transport on typical severe air pollution episodes. There were on average eight days of severe air pollution (AQI >200) in 2015 in each city, and PM _2.5 was the primary contributor. High AQI days were mainly concentrated in January and December. Spatially, monitoring data indicated more frequent high pollution days in the northern region of the YRD as compared to the southern region. In particular, Xuzhou city and Changzhou city had seen the most frequent high pollution days. We then analyzed three representative large regional episodes, i.e., a "north-south diffusion type" during January 9-11, an "east-west diffusion type" during January 24-26, and a "multi-process diffusion type" during December 20-26. During these heavy air pollution episodes, the predominant wind was of northwesterly direction, and the atmosphere was more stagnant as indicated by lower wind speeds and high relative humidity. Analysis of the backward trajectories and frequency distributions showed that the airflow from the northwest had an important influence on the transport of air pollutants in the YRD and particularly the northern region of Jiangsu Province.