Urban Climate 35 (2021) 100758 2212-0955/© 2020 Elsevier B.V. All rights reserved. Spatio-temporal concentration of atmospheric particulate matter (PM 2.5 ) during pandemic: A study on most polluted cities of indo-gangetic plain Manob Das a , Arijit Das a , Sasanka Ghosh b , Raju Sarkar c, * , Sunil Saha a a Department of Geography, University of Gour Banga, Malda 732103, West Bengal, India b Department of Geography, Kazi Nazrul University, Asansol 713340, West Bengal, India c Department of Civil Engineering, Delhi Technological University, Bawana Road, Delhi 110042, India A R T I C L E INFO Keywords: Lockdown COVID-19 Air quality Particulate matter (PM) Indo-Gangetic plain (IGP) ABSTRACT COVID-19 pandemic exhibited the entire world two aspects: human threats and environmental restoration. Due to pandemic, the nationwide lockdown in India imposed on 25 March and continued till 31 May 2020 in different phases. Again partial withdrawl of restrictions started from UnlockI (1–30 June 2020) to revive the Indian economy partially. The present research focused to assess impact of lockdown on the concentration of particulate matter (PM 2.5 ) across the ten most polluted cities of Indo-Gangetic Plain of India alongwith incorporation of spatial dis- tribution of PM 2.5 hotspots. It observed that during lockdown, the average concentration of PM 2.5 (μg/m 3 ) across the cities decreased from 197 to 79 which is decrease of 60% since pre lockdown. In January 2020, the cities under considerations were in the category of ‘severe’ air quality index (AQI) but from March no cities fall under this category. The hotspot maps showed that in last three years (2017–2019), relatively higher concentration of PM 2.5 was observed mostly around Delhi NCR but during same period of 2020 (lockdown and Unlock I), this con- centartion decreased substantially. The fndings of the study suggest that only by effective policies like short term lockdown, implementation of odd and even number motor vehicles, relocation of polluted industries need to be implemented by central and state governmental authorities to achive environmental sustainability. 1. Introduction The COVID-19 has now become a global health concern (Das et al., 2020a) caused by SARS-CoV-2 virus due to its rapid spreading across the entire world (World Health Organization (WHO), 2020). As of 8th August 2020, nearly 20 million people has been infected across the world with deaths about 0.7 million deaths (World Health Organization (WHO). Report of the WHO-China Joint Mission on Corona Virus Disease 2019 (COVID-19), 2020). Few considerable combating measures have been adopted to restrict the spread of ths pandemic by restricting travel, lockdown, maintenance of social distancing etc. Among all the measures, lockdown has impacted all the sphere of the environment-such as social, economic as well as environmental. This pandemic has been declared as ‘social, human and economic crises’ by United Nation (2020). A prediction was made by Congressional Research Service (2020) that annual gross * Corresponding author. E-mail address: rajusarkar@dce.ac.in (R. Sarkar). Contents lists available at ScienceDirect Urban Climate journal homepage: www.elsevier.com/locate/uclim https://doi.org/10.1016/j.uclim.2020.100758 Received 9 September 2020; Received in revised form 30 October 2020; Accepted 4 December 2020