外来输送对江苏冬季PM2.5贡献的数值模拟研究

利用WRF-Chem模式对2016年12月中下旬的两次重污染过程进行模拟，定量研究外来污染输送对江苏省PM_2.5的污染贡献。15—17日和22—23日两次过程都存在明显的上游污染输送特征:宿迁、扬州、无锡(自西北向东南)的PM_2.5浓度先后出现峰值，峰值均出现在西北风场中，当风向转为偏北风时峰值逐渐减弱。第二次过程中地面风力更大，高空形势更有利于远距离输送，高值区范围强度明显强于第一次，重度污染层厚度达到900~1 500 m，且持续时间较长。第一次过程中江苏省内排放源贡献率为23%~79%(第二次为5%~32%)，苏南仍以本地排放源污染为主，苏北外来输送贡献率超过50%。第二次过程中宿迁、扬州、无锡的PM_2.5外来输送贡献分别为105.9 μg/m3、83.1 μg/m3、64.8 μg/m3(第一次为40.2 μg/m3、20.9 μg/m3、11.1 μg/m3)，山东省和京津冀地区排放源是主要污染输送来源，二者贡献之和在44%~70%。两次过程中，外来输送贡献均是自北向南递减，山东省贡献率高于京津冀地区，而其余周边省份的贡献率相对较低；安徽省对江苏西部城市的贡献率较高。 

A NUMERICAL SIMULATION STUDY ON THE CONTRIBUTION OF POLLUTION TRANSPORT TO PM2.5 IN JIANGSU DURING WINTERTIME

In order to reveal the contribution of pollution transport to PM_2.5 in Jiangsu, WRF-Chem model was used to simulate heavy pollution episodes during December 14—24, 2016. The results showed that Episode1(15—17) and Episode2(22—23) both had obvious features of upstream pollution transport: the PM_2.5 concentration peak value appeared successively from northwest to southeast when surface was dominated by the northwest wind and decreased when wind direction changed to northerlies. The extension and intensity of high value in Episode2 was much higher than that in Episode1, during which the wind was stronger, the upper-level synoptic pattern was more favorable to long-distance transport, the severe pollution layer height reached 900~1 500 m, and the life-span was longer. The contribution ratio of emission resources in Jiangsu reached 23%~79% in Episode1 (and 5%~32% in Episode2). The ratio of transport was over 50% in northern Jiangsu while less than 50% in southern Jiangsu. In Episode2, the contribution of PM_2.5 transport in Suqian, Yangzhou and Wuxi were 105.9 μg/m3, 83.1 μg/m3, and 64.8 μg/m3(40.2 μg/m3, 20.9 μg/m3, and 11.1 μg/m3, respectively in Episode1). Shandong and Beijing-Tianjin-Hebei region contributed 44%~70% together as far as pollution transport is concerned. In both Episodes, the contribution of PM_2.5 transport decreased from north to south. Shandong played a more important role of pollution transportation than Beijing-Tianjin-Hebei region, and the other regions were relatively less important. Anhui had a high contribution rate on the western cites of Jiangsu.