COVID-19 strict lockdown impact on urban air quality and atmospheric temperature in four megacities of India

Subodh Chandra Pal; Indrajit Chowdhuri; Asish Saha; Manoranjan Ghosh; Paramita Roy; Biswajit Das; Rabin Chakrabortty; Manisa Shit

doi:10.1016/j.gsf.2022.101368

COVID-19 strict lockdown impact on urban air quality and atmospheric temperature in four megacities of India

Geosci Front. 2022 Nov;13(6):101368. doi: 10.1016/j.gsf.2022.101368. Epub 2022 Feb 9.

Authors

Subodh Chandra Pal¹, Indrajit Chowdhuri¹, Asish Saha¹, Manoranjan Ghosh^{2

3}, Paramita Roy¹, Biswajit Das¹, Rabin Chakrabortty¹, Manisa Shit⁴

Affiliations

¹ Department of Geography, The University of Burdwan, Bardhaman, 713104, West Bengal, India.
² Center for Rural Development and Innovative Sustainable Technology, Indian Institute of Technology Kharagpur, West Bengal, 721302, India.
³ India Smart Cities Fellow, National Institute of Urban Affairs, New Delhi, 110003, India.
⁴ Department of Geography, Raiganj University, Raiganj, Uttar Dinajpur, 733134, West Bengal, India.

Abstract

COVID-19 pandemic has forced to lockdown entire India starting from 24th March 2020 to 14th April 2020 (first phase), extended up to 3rd May 2020 (second phase), and further extended up to 17th May 2020 (third phase) with limited relaxation in non-hotspot areas. This strict lockdown has severely curtailed human activity across India. Here, aerosol concentrations of particular matters (PM) i.e., PM₁₀, PM_2.5, carbon monoxide (CO), nitrogen dioxide (NO₂), sulphur dioxide (SO₂), ammonia (NH₃) and ozone (O₃), and associated temperature fluctuation in four megacities (Delhi, Mumbai, Kolkata, and Chennai) from different regions of India were investigated. In this pandemic period, air temperature of Delhi, Kolkata, Mumbai and Chennai has decreased about 3 °C, 2.5 °C, 2 °C and 2 °C respectively. Compared to previous years and pre-lockdown period, air pollutants level and aerosol concentration (-41.91%, -37.13%, -54.94% and -46.79% respectively for Delhi, Mumbai, Kolkata and Chennai) in these four megacities has improved drastically during this lockdown period. Emission of PM_2.5 has experienced the highest decrease in these megacities, which directly shows the positive impact of restricted vehicular movement. Restricted emissions produce encouraging results in terms of urban air quality and temperature, which may encourage policymakers to consider it in terms of environmental sustainability.

Keywords: Aerosol; Air pollutant; COVID-19; Climate; Megacity.