Variations of Urban NO2 Pollution during the COVID-19 Outbreak and Post-Epidemic Era in China: A Synthesis of Remote Sensing and In Situ Measurements

Remote Sensing

Chengxin Zhang¹  Chunhui Zhao²  Shuntian Wang²  Jinan Lin²  Cheng Liu²  Hanyang Liu³  Hongyu Wu⁴ 

[1] Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230026, China;Key Laboratory of Environmental Optics & Technology, Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China;School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China;School of Environmental Science and Optoelectronic Technology, University of Science and Technology of China, Hefei 230026, China;

关键词: NO₂;    COVID-19;    air pollution;    satellite remote sensing;    TROPOMI;   

DOI  :  10.3390/rs14020419

来源: DOAJ

【 摘 要 】

Since the COVID-19 outbreak in 2020, China’s air pollution has been significantly affected by control measures on industrial production and human activities. In this study, we analyzed the temporal variations of NO₂ concentrations during the COVID-19 lockdown and post-epidemic era in 11 Chinese megacities by using satellite and ground-based remote sensing as well as in situ measurements. The average satellite tropospheric vertical column density (TVCD) of NO₂ by TROPOMI decreased by 39.2–71.93% during the 15 days after Chinese New Year when the lockdown was at its most rigorous compared to that of 2019, while the in situ NO₂ concentration measured by China National Environmental Monitoring Centre (CNEMC) decreased by 42.53–69.81% for these cities. Such differences between both measurements were further investigated by using ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) remote sensing of NO₂ vertical profiles. For instance, in Beijing, MAX-DOAS NO₂ showed a decrease of 14.19% (versus 18.63% by in situ) at the ground surface, and 36.24% (versus 36.25% by satellite) for the total tropospheric column. Thus, vertical discrepancies of atmospheric NO₂ can largely explain the differences between satellite and in situ NO₂ variations. In the post-epidemic era of 2021, satellite NO₂ TVCD and in situ NO₂ concentrations decreased by 10.42–64.96% and 1.05–34.99% compared to 2019, respectively, possibly related to the reduction of the transportation industry. This study reveals the changes of China’s urban NO₂ pollution in the post-epidemic era and indicates that COVID-19 had a profound impact on human social activities and industrial production.

【 授权许可】

Unknown