[Characteristic analysis of a multi-day pollution event in Chang-Zhu-Tan Metropolitan Area during October 2013]

Chang-Zhu-Tan Metropolitan Area experienced a typical multi-day pollution event in October 2013. Based on the air pollution index, conventional pollutants observations, surface meteorological observations and sounding data, the relationships of air pollution, large-scale circumfluence and boundary layer meteorology of this event were comprehensively analyzed. Additionally, the sources and transport paths of pollutions were investigated by application of satellite remote sensing data and HYSPLIT4 model. The results showed that pollutants gradually accumulated in the earlier stage of the event (October 21th to 26th) , while in the later stage (October 27th to 31th) the characteristic pollutants of crop residue burning (PM2.5, CO, NO2) sharply increased. The deterioration of air quality in the later stage was mainly related to the remote transport of pollutants caused by straw burning. Analysis of simulations of HYSPLIT4 model and fire spots showed that the currents mainly came from Anhui and Hubei Province in the earlier stage, while in the later stage they were mainly from Jiangxi Province where fire spots were intensively located. Stable atmospheric stratification caused by steady uniform high-pressure field and slight wind due to the confrontation of cold and warm currents greatly contributed to the development, maintainability and reinforcement of the pollution event. The remote transport of pollutants had a significant impact on ambient air quality of Chang-Zhu-Tan Metropolitan Area.