Air Quality Change and Improvement Measures during the COVID-19 Epidemic in Wuhan

From 23 January 2020, strict traffic control measures have been implemented in Wuhan, which has had a significant impact on human activities in Wuhan. This study analyzes the changes of the main atmospheric components in Wuhan during the lockdown based on ground monitoring stations and satellite remote sensing. Moreover, the study shows the effects of anthropogenic emissions on O₃ and PM2.5 pollution. Compared with the observed values in the same period of 2019, the results showed that the banning of motor vehicles reduced NO₂ concentration and VOCs (mainly low-activity alkanes) in Wuhan by 53.2% and 25.1%, respectively. On the other hand, the maximum 8-h moving average 90th percentile of the O₃ concentration increased by 16.5% compared with the same period last year. Particularly in February, when the temperature was comparatively 5 °C higher than usual with an increase in surface UV radiation by 100%, O₃ concentration was much higher. This is suggested that the nonlinear quantitative relationship between the NO₂ and VOC active species in O₃ generation should be used to promote collaborative emission reduction. Meanwhile, PM2.5 reduced by 35.6%, which was mainly concentrated in February under favorable meteorological conditions. The reduction of nitrate in PM2.5 was not as obvious in March compared with that in February, indicating that the main driving effects of the atmospheric oxidation capacity in nitrate formation still exist. Therefore, the control of primary particles and key precursors must be strengthened in the emission reduction of particulate matter in Wuhan.