Special Issue on COVID-19 Aerosol Drivers, Impacts and Mitigation

Parichat Wetchayont This email address is being protected from spambots. You need JavaScript enabled to view it.1, Tadahiro Hayasaka2, Pradeep Khatri2


1 Department of Geography, Faculty of Social Science, Srinakharinwirot University, Bangkok, Thailand
2 Center for Atmospheric and Oceanic Studies, Graduate School of Science, Tohoku University, Sendai, Japan

Received: December 14, 2020
Revised: February 13, 2021
Accepted: March 10, 2021

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

Download Citation: ||https://doi.org/10.4209/aaqr.200662  

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Cite this article:

Wetchayont, P., Hayasaka, T., Khatri, P. (2021). Air Quality Improvement during COVID-19 Lockdown in Bangkok Metropolitan, Thailand: Effect of the Long-range Transport of Air Pollutants. Aerosol Air Qual. Res. https://doi.org/10.4209/aaqr.200662


  • Air quality has improved significantly during the COVID-19 lockdown.
  • Surface NO2 and SO2 increased due to the long-range transport pollutions.
  • Lockdown measures has no impact on air pollution at the upper level.


Lockdown measures have been adopted in many countries worldwide due to the onset of the COVID-19 pandemic, including in Thailand. Air quality improvements with regard to restrictions of daily movement among Bangkok people have been reported. This study explores the impact of the COVID-19 outbreak and long-range pollution on air quality in Bangkok Metropolitan, Thailand by using ground-based and satellite measurements such as MODIS and TROPOMI data. Moreover, the results project some possible future trends of air quality in Bangkok Metropolitan. The 24-hr average concentrations of PM2.5, O3, NO2, CO and SO2 were compared between the periods of Normal, Lockdown and New Normal. PM2.5 concentrations increased by 20.56% during the Normal period and decreased by -15.79% and -23.34% during the Lockdown and New Normal periods, respectively, compared to the same periods in 2017–2019. There were also significant decreasing trends in O3: -7.13% and 4.72%; and CO -8.01% and 23.59% during the Lockdown and New Normal periods, respectively, while NO2 and SO2 concentrations showed increasing trends during the three periods. The MODIS and TROPOMI data analyses indicate the COVID-19 outbreak has had significant positive impact on surface pollution, but no impact on upper atmospheric pollution due to added pollution from long-range transport. The results also demonstrate that surface air pollution had a combination effect from biomass burning, traffic, industrial and household sources during the Lockdown period, except for SO2 concentrations, which were attributed to long-range transport pollution loading. In some cases, a negative impact of the COVID-19 lockdown on air pollution can be observed due to certain activities increasing within Bangkok Metropolitan. Additionally, the results also show that changing the lifestyle into a ‘new normal’ for people in Bangkok after the Lockdown period has had a positive effect on air pollution.

Keywords: COVID-19, Pollution, Long-range air pollution, PM2.5, Bangkok, Thailand

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