The Impact of COVID-19 on Urban PM <sub>2.5</sub> —Taking Hubei Province as an Example

Abstract

In January 2020, China adopted strict lockdown measures due to the invasion of the new coronavirus, which led to a sharp decline in the contribution of anthropogenic PM2.5. The special period of COVID-19, especially in Hubei where the epidemic was the most severe, provides excellent research conditions for studying the contribution of anthropogenic activities to PM2.5 concentrations. We used an optimized deep learning model to predict the PM2.5 concentration during the epidemic period in the cities of Hubei Province. The contributions of local anthropogenic activities to PM2.5 pollution were obtained by comparing the predicted results with actual site observations. Among the contributions of anthropogenic activities on PM2.5 during the COVID-19 lockdown, Huanggang, the city with the largest decline, decreased by 34.40%; the most severely affected area, Wuhan, decreased by 26.38%; and Hubei Province decreased by 22.61% on average. However, a strange phenomenon was discovered. Xiangyang and Yichang are the second and third largest cities in Hubei Province in terms of industrial output value. Severe smog is observed every winter, but low local anthropogenic contributions to PM2.5 were found in these cities, conflicting with our previous expectations. Through an analysis of backward air-mass trajectory and an analysis of changes in the main pollution components, we believe that an increased conversion of secondary aerosols caused by long-distance transmission of pollutant gases from the Beijing-Tianjin-Hebei region is the main cause of winter haze pollution in these two cities. This finding highlights the importance of joint regional prevention and control of air pollution.