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Variation Characteristics and Source Analysis of Pollutants in Jinghong before and after the COVID-19 Pandemic

With the outbreak of COVID-19 in early 2020, China’s urban epidemic prevention and control policies have caused significant changes in air pollution sources. In order to clarify the change characteristics of urban air pollution in Yunnan Province before and after the epidemic, using statistics and correlation analysis methods, Jinghong city was selected as the research object, and based on the ambient air quality monitoring data (SO2, NO2, CO, O3, PM2.5, and PM10) and meteorological data from 2017 to 2021, the concentration characteristics of air pollutants in Jinghong in the past five years were analyzed, and the sources of air pollutants were analyzed using the local emission source inventory and HYSPLIT model. The results show that: ① The air quality in Jinghong was the worst in 2019 before the outbreak of the epidemic, and then gradually improved, with an average 5-year excellent and good rate of 91.8%. The pollutants are mainly particulate matter and O3. ② Except for SO2, the concentrations of other pollutants have similar seasonal changes, with the highest in spring and the lowest in summer. ③ The air quality in Jinghong is mainly affected by the combined effects of local emissions and external transportation. According to the local emission inventory, biomass combustion sources have the largest contribution to CO, PM2.5, and PM10, mobile sources have the highest share rate of NOx, and industrial enterprises are the largest emission sources of SO2. Air mass backward trajectory research shows that the westward and southerly airflow are the main transport direction of pollutants entering Jinghong, especially in spring, which significantly affects the local pollutant concentration level. In addition, meteorological conditions such as temperature, precipitation, and wind speed also have a great impact on the dilution, diffusion, and transfer of air pollutants in Jinghong. The results of this study further improve the characteristics of the spatial and temporal distribution of air pollutants and pollutant sources in the border areas of China and before and after the epidemic, and also provide a theoretical basis for air environment management in the border areas.