Abstract: Affected by the COVID-19 epidemic, the activity level of Wuhu residents has been reduced to the lowest level during the Spring Festival in 2020 (from January 24 to February 8). However, there were three different air pollution events occurred in Wuhu city, which provided an opportunity for exploring the cause of air pollution in Wuhu. The pollution characteristics and causes of the three pollution events are analyzed based on the monitoring data of ground meteorological elements, lidar monitoring data and HYSPLIT backward trajectory model. The results show that the first pollution event from 8:00 on January 27 to 18:00 on January 28 is a 10-hour transient pollution process induced by the high humidity and static atmospheric environment with the local basic emissions unchanged. The second pollution event from 17:00 on January 29 to 13:00 on February 1 is caused by a long-distance and longterm transportation of polluted air masses from Hebei, Henan and Shandong provinces, which intensifies the degree of pollution, and finally induces a two-day light pollution from January 30 to 31 under the increased emissions from key enterprises and unfavorable atmospheric diffusion conditions. And the third pollution event from 19:00 on February 2 to 07:00 on February 4 is a day light pollution caused by the short-term input of pollution groups from Jiangsu and Zhejiang provinces under the unfavorable diffusion conditions. Compared with the Spring Festival in 2019, the air quality in 2020 has improved significantly, the number of days of moderate and above pollution has decreased by 100%, and the pollution duration of light pollution has decreased by 48 hours. It can be seen that local source emission reduction is the fundamental to improve the air quality of Wuhu, and regional joint prevention and control is an effective means to deal with the polluted weather.

Key words: air pollution event, Wuhu, back trajectory model, aerosol lidar