Analysis of the Impact of Meteorological Factors on Ambient Air Quality during the COVID-19 Lockdown in Jilin City in 2022

This paper explored the changes of six significant pollutants (PM2.5, PM10, SO2, NO2, O-3, and CO) in Jilin City during the coronavirus disease 2019 (COVID-19) epidemic in 2022, and compared them with the same period of previous years to analyze the impact of anthropogenic emissions on the concentration of pollutants; The Weather Research and Forecasting Community Multiscale Air Quality (WRF-CMAQ) model was used to evaluate the effect of meteorological factors on pollutant concentration. The results showed that except for O-3, the concentrations of the other five pollutants decreased significantly, with a range of 21-47%, during the lockdown period caused by the government's shutdown and travel restrictions. Compared with the same period in 2021, the decrease of PM2.5 was only 25% of PM10. That was because there was still a large amount of PM2.5 produced by coal-fired heating during the blockade period, which made the decrease of PM2.5 more minor. A heavy pollution event caused by adverse meteorological conditions was found during the lockdown period, indicating that only controlling artificial emissions cannot eliminate the occurrence of severe pollution events. The WRF-CMAQ results showed that the lower pollutant concentration in 2022 was not only caused by the reduction of anthropogenic emissions but also related to the influence of favorable meteorological factors (higher planetary boundary layer thickness, higher wind speed, and higher temperature).