Numerical simulations of PM2.5 pollution source in the Yangtze River Delta region in fall and winter in 2018

This paper used WRF-Chem and WRF-FLEXPART to quantify the source contribution to PM2.5 of the Yangtze River Delta (YRD) region during fall and winter in 2018, especially during the cold air processes. The results showed that the contribution to PM2.5 of the YRD region from inter-regional transport accounted for 15.9%, while the contribution from local emission and intra-regional transport accounted for 84.1%, which indicated that the influence of local emission and intra-regional pollution transport was much more significant than that of inter-regional transport. During cold air processes, the contribution to PM2.5 in the YRD region from intra-regional transport increased to around 33.1%, approximately twice of the average contribution during the whole fall and winter in 2018. The contribution to each provincial region in the YRD region from both intra- and inter-regional transport ranged from 46.2% to 56.2%, among which the inter-regional transport ranged between 10.2% and 38.6%. They were significantly above the averages in the fall and winter. During cold air processes, the potential pollution transport pathways affecting the 4 major cities (Shanghai, Hefei, Nanjing and Hangzhou) was along the mid-and-east pathway. The potential pollution contribution from external YRD regions to Shanghai and Nanjing were more than 30%, while that to Hangzhou was smallest at around 16.1%. © 2020, Editorial Board of China Environmental Science. All right reserved.