In the course of COVID- 19 pandemic, a nationwide lockdown in India has been imposed from 22nd March 2020 extended to June end, thereafter a partial lockdown was enforced as a precautionary measure to confine the spread of COVID- 19. The anthropogenic activity was restricted during lockdown therefore the pollution level across many cities in India reduced drastically. This eventually led us to analyze the air quality scenario of Kolkata metropolitan city along with suburban areas of North 24 Parganas and Howrah in the state of West Bengal, India. In the present research, the air quality parameters like PM10, PM2.5, SO2, NO2, CO, O3, and NH3 were analyzed the during lockdown phase of 23rd March 2020 to 30th June 2020. A comparative study was done with the air quality data of the pre-lock down phase (March 2019 to 4th March 2020) and an Air Quality Index (AQI) was prepared. During lockdown coal/ fuel consumption was low due to the restriction of vehicle movement and road transport thus carbon emission in the air was less. AQI improved enormously with reduction of SO2 content to <80 %; among other pollutants NO2 and NH3 reduced to <54 % and <91 % in Kolkata, Howrah, and 24 Parganas North. P.M 2.5 drastically reduced in the regions of Kolkata, Howrah, and 24 Parganas North of West Bengal effectively to <81%, <91 %, and <95% respectively. P.M 10 reduced to <75%, <79%, and < 81 % in Kolkata, Howrah, and 24 Parganas North. In Kolkata there was 55% reduction in the level of CO. There was 4 folds reduction of P.M2.5 and P.M10 in Kolkata compared to March- June 2019. About 50 % to 60 % improvement in air quality was identified within 7days of the lockdown. Improvement of air quality during lockdown has benefited the environment and ecology.
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