Abstract
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.
Highlights
Novel Coronavirus or COVID-19, the greatest pandemic of the century (WHO, 2020) poses unprecedented situations for human survival in the world
The present study investigated daily pollution change during COVID-19 lockdown over Chennai
There is an increase in relative humidity (RH) (~10%), decrease in air temperature (~2°C) and increase in wind speed (~2 m s–1) during COVID-19 lockdown over Chennai
Summary
Novel Coronavirus or COVID-19, the greatest pandemic of the century (WHO, 2020) poses unprecedented situations for human survival in the world. Kumar et al (2020) studied fine particulate matter using satellite derived Aerosol Optical Depths (AOD) and in-situ observed hourly data by U.S Embassy over five megacities of India (Delhi, Kolkata, Mumbai, Chennai and Hyderabad) during COVID-19 lockdown. They found that aerosol loading decreased 29% over Chennai with considerable improvements in premature deaths. The present study will attempt to analyse the pollution change of five criterion pollutants (i.e., PM2.5, NOx, O3, CO and SO2) during the COVID-19 lockdown at five different sites in the city: Teynampet, Alandi, Velachery, Manali and U.S Embassy.
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