Spatio-temporal concentration of atmospheric particulate matter (PM2.5) during pandemic: A study on most polluted cities of indo-gangetic plain

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 (PM2.5) across the ten most polluted cities of Indo-Gangetic Plain of India alongwith incorporation of spatial distribution of PM2.5 hotspots. It observed that during lockdown, the average concentration of PM2.5(mu g/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 PM2.5 was observed mostly around Delhi NCR but during same period of 2020 (lockdown and Unlock I), this concentartion decreased substantially. The findings 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.