The Role of Primary Emission and Transboundary Transport in the Air Quality Changes During and After the COVID‐19 Lockdown in China

• Published in: Geophysical Research Letters 2021-04, Vol.48 (7), p.e2020GL091065-n/a
• Main Authors: Fan, Hao, Wang, Yuan, Zhao, Chuanfeng, Yang, Yikun, Yang, Xingchuan, Sun, Yue, Jiang, Shuyi
• Format: Article
• Language: English
• Subjects: Aerosols; Aerosols and Particles; air pollutants; Atmospheric Composition and Structure; Biogeosciences; China; COVID‐19; emission; lockdown; Marine Pollution; Megacities and Urban Environment; Natural Hazards; Oceanography: Biological and Chemical; Oceanography: General; Paleoceanography; Pollution: Urban and Regional; Pollution: Urban, Regional and Global; Research Letter; The COVID‐19 pandemic: linking health, society and environment; Urban Systems
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2020GL091065

In late January 2020, China’s rapid and strict control measures to curb the COVID‐19 spread led to a sharp halt in socio‐economic activity and a significant reduction in emissions. Using the ground‐based observational data, the authors synergistically quantify the nation‐wide variations of major air pollutant as well as meteorology during and after the lockdown. Their concentrations (except O3) exhibited significant reduction during February and March 2020, by more than 24% during the lockdown compared with the earlier time period and by more than 17% compared with that in the same period in 2019. In contrast, ozone increased rapidly by about 60% across the country during the lockdown. Abnormal increases in carbon monoxide and particulate matter concentrations in southwest China are attributed to the severe wildfires in Southeast Asia. The concentration of air pollutants bounced back rapidly after the full‐scale reopen in March 2020, indicating the decisive role of emissions in the pollution formation. Plain Language Summary Previous studies have reported unexpected increases in air pollution over certain region during the first few weeks of the pandemic in China, due to strong modulation from meteorological variations and complex atmospheric chemistry. Here, we show that on the national scale, the major air pollutants (other than ozone [O3]) still exhibited significant reduction between February and March 2020. The concentration of major pollutants fell by more than 24% during the lockdown period compared with that before the lockdown and by more than 17% compared with that in the same period in 2019. In contrast, ozone showed rapid growth of about 60% across the country during the lockdown, which underscores the importance of coordinated management of PM (particulate matter) and O3. The concentration of air pollutants bounced back rapidly after March 2020. We also find increases in CO and PM concentrations in southwest China due to abnormal wildfires in Southeast Asia, revealing the nonnegligible influence of transboundary transport of pollutants in the regional scale. Key Points Significant air pollutant changes during and after the lockdown implies that emission is still the primary driver of nationwide air pollution Ozone showed rapid growth of about 60% across the country during the lockdown Southeast Asia wildfires caused an abnormal increase in carbon monoxide (CO) and particulate matter (PM) in southwest China