NOx Emission Reduction and Recovery: Comparison
Please note this is a comparison between Version 1 by Ruixiong Zhang and Version 3 by Rita Xu.

Since its first confirmed case at the end of 2019, COVID-19 has become a global pandemic in three months with more than 1.4 million confirmed cases worldwide, as of early April 2020. Quantifying the changes of pollutant emissions due to COVID-19 and associated governmental control measures is crucial to understand its impacts on economy, air pollution, and society. We used the WRF-GC model and the tropospheric NO

2

column observations retrieved by the TROPOMI instrument to derive the top-down NOx emission change estimation between the three periods: P1 (January 1

st

to January 22

nd

, 2020), P2 (January 23

rd

, Wuhan lockdown, to February 9

th

, 2020), and P3 (February 10

th

, back-to-work day, to March 12

th

, 2020). We found that NOx emissions in East China averaged during P2 decreased by 50% compared to those averaged during P1. The NOx emissions averaged during P3 increased by 26% compared to those during P2. Most provinces in East China gradually regained some of their NOx emissions after February 10, the official back-to-work day, but NOx emissions in most provinces have not yet to return to their previous levels in early January. NOx emissions in Wuhan, the first epicenter of COVID-19, had no sign of emission recovering by March 12. A few provinces, such as Zhejiang and Shanxi, have recovered fast, with their averaged NOx emissions during P3 almost back to pre-lockdown levels.

  • COVID-19
  • air pollutant emission
  • TROPOMI
  • NO2
  • NOx
  • economic activity
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