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

Jyotsna Singh1, Bhishma Tyagi This email address is being protected from spambots. You need JavaScript enabled to view it.2

1 Shanti Raj Bhawan, Paramhans Nagar, Kandwa, Varanasi, India
2 Department of Earth and Atmospheric Sciences, National Institute of Technology Rourkela, Rourkela, India

Received: July 31, 2020
Revised: November 12, 2020
Accepted: December 21, 2020

 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.200490  

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Cite this article:

Singh, J., Tyagi, B. (2021). Transformation of Air Quality over a Coastal Tropical Station Chennai during COVID-19 Lockdown in India. Aerosol Air Qual. Res. 21, 200490. https://doi.org/10.4209/aaqr.200490


  • The pollutants variation is not uniform during COVID-19 lockdown at different sites of Chennai.
  • SO2 have increased at Teynampet and Velachery but reduced at Alandur and Manali.
  • NOx, PM2.5 and CO decreased at all sites during the lockdown period.
  • The weekly analysis shows non-uniformity in reduction with increased values at some weeks.
  • CWT analysis reveals different source regions pattern during the lockdown period.


To prevent the spread of COVID-19, Government of India imposed strict lockdown in the country from 24 March–31 May 2020, which allows the environment to revive with reduced emissions. The present work analyses the PM2.5, NO2, O3, CO and SO2 along with meteorological parameters (humidity, temperature and wind speed) at a tropical coastal station Chennai for March-May 2019 and 2020 at five locations: Alandur Bus depot, Velachery, Manali, Teynampet and U.S. Embassy Chennai. Chennai is a megacity of southern India and the state capital of Tamil Nadu, one of the worst affected states due to COVID-19. Though overall PM2.5 values decreased for the lockdown (ranging from ~32–187%), weekly analysis shows the variation in reduction/increase. SO2 and O3 values were found increasing for two sites: Teynampet (~40% in SO2 and ~48% in O3) and Velachery (~42% in SO2 and ~5% in O3), but decreasing for Alandur (~30% in SO2 and ~50% in O3) and Manali (~247% in SO2). NOx and CO were reduced during the lockdown (~47–125%) for all the sites. The source regions examined by concentration weighted trajectory analysis were found to change for transporting pollution to the site. The analysis shows there are local scale variations in the air pollution for the city during COVID-19 lockdown.

Keywords: COVID-19, CWT analysis, Particulate Matter, Nitrogen dioxide, Sulphur dioxide

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