Spring festival and COVID-19 lockdown: disentangling PM sources in major Chinese cities

Research output: Contribution to journalArticlepeer-review


  • Qili Dai
  • Linlu Hou
  • Yufen Zhang
  • Philip K. Hopke
  • Yinchang Feng

External organisations

  • Nankai University
  • University of Rochester
  • Clarkson University


Responding to the 2020 COVID-19 outbreak, China imposed an unprecedented lockdown producing reductions in air pollutant emissions. However, the lockdown driven air pollution changes have not been fully quantified. We applied machine learning to quantify the effects of meteorology on surface air quality data in 31 major Chinese cities. The meteorologically normalized NO2, O3, and PM2.5 concentrations changed by −29.5%, +31.2%, and −7.0%, respectively, after the lockdown began. However, part of this effect was also associated with emission changes due to the Chinese Spring Festival, which led to ∼14.1% decrease in NO2, ∼6.6% increase in O3 and a mixed effect on PM2.5 in the studied cities that largely resulted from festival associated fireworks. After decoupling the weather and Spring Festival effects, changes in air quality attributable to the lockdown were much smaller: −15.4%, +24.6%, and −9.7% for NO2, O3, and PM2.5, respectively.

Bibliographic note

Funding Information: This work was funded by the Ministry of Science and Technology of the People's Republic of China (2016YFC0208505). Publisher Copyright: © 2021. The Authors.


Original languageEnglish
Article numbere2021GL093403
Number of pages12
JournalGeophysical Research Letters
Issue number11
Early online date1 Jun 2021
Publication statusPublished - 16 Jun 2021


  • air quality, COVID-19, machine learning, meteorological normalization, source, spring festival

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