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      Effect of lockdown amid COVID-19 pandemic on air quality of the megacity Delhi, India

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          Abstract

          Amid the COVID-19 pandemic, a nationwide lockdown is imposed in India initially for three weeks from 24th March to 14th April 2020 and extended up to 3rd May 2020. Due to the forced restrictions, pollution level in cities across the country drastically slowed down just within few days which magnetize discussions regarding lockdown to be the effectual alternative measures to be implemented for controlling air pollution. The present article eventually worked on this direction to look upon the air quality scenario amidst the lockdown period scientifically with special reference to the megacity Delhi. With the aid of air quality data of seven pollutant parameters (PM 10, PM 2.5, SO 2, NO 2, CO, O 3 and NH 3) for 34 monitoring stations spread over the megacity we have employed National Air Quality Index (NAQI) to show the spatial pattern of air quality in pre and during-lockdown phases. The results demonstrated that during lockdown air quality is significantly improved. Among the selected pollutants, concentrations of PM 10 and PM 2.5 have witnessed maximum reduction (>50%) in compare to the pre-lockdown phase. In compare to the last year (i.e. 2019) during the said time period the reduction of PM 10 and PM 2.5 is as high as about 60% and 39% respectively. Among other pollutants, NO 2 (−52.68%) and CO (−30.35%) level have also reduced during-lockdown phase. About 40% to 50% improvement in air quality is identified just after four days of commencing lockdown. About 54%, 49%, 43%, 37% and 31% reduction in NAQI have been observed in Central, Eastern, Southern, Western and Northern parts of the megacity. Overall, the study is thought to be a useful supplement to the regulatory bodies since it showed the pollution source control can attenuate the air quality. Temporary such source control in a suitable time interval may heal the environment.

          Graphical abstract

          Highlights

          • PM 10 and PM 2.5 concentrations reduced by about half in compare to the pre-lockdown

          • NO 2 and CO have also shown considerable decline during lockdown.

          • In the transportation and industrial location air quality have improved close to 60%.

          • The central and Eastern Delhi have experienced maximum improvement in air quality.

          • On the 2nd and 4th day of lockdown, about 40% to 50% improvement in air quality

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          Author and article information

          Contributors
          Journal
          Sci Total Environ
          Sci. Total Environ
          The Science of the Total Environment
          Elsevier B.V.
          0048-9697
          1879-1026
          29 April 2020
          29 April 2020
          : 139086
          Affiliations
          Department of Geography, University of Gour Banga, West Bengal, India
          Department of Geography, Presidency University, West Bengal, India
          Author notes
          [* ]Corresponding author. krishna.geog@ 123456presiuniv.ac.in
          Article
          S0048-9697(20)32603-6 139086
          10.1016/j.scitotenv.2020.139086
          7189867
          32375105
          bf3730ec-a2c8-456a-8134-0ff07348de96
          © 2020 Elsevier B.V. All rights reserved.

          Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.

          History
          : 25 April 2020
          : 26 April 2020
          : 27 April 2020
          Categories
          Article

          General environmental science
          covid-19,lockdown,megacity delhi,national air quality index,change of air quality

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