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

• Published in: The Science of the total environment Vol. 730; p. 139086
• Main Authors: Mahato, Susanta, Pal, Swades, Ghosh, Krishna Gopal
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.08.2020
• Subjects: Air Pollutants; Air Pollution; air quality; Betacoronavirus; Change of air quality; Cities; Coronavirus Infections; COVID-19; COVID-19 infection; environment; Environmental Monitoring; Humans; India; Lockdown; Megacity Delhi; National Air quality Index; Pandemics; Particulate Matter; Pneumonia, Viral; pollutants; SARS-CoV-2; Cities; India; Lockdown; Change of air quality; Megacity Delhi; Covid-19; National Air quality Index
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.139086

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 (PM10, PM2.5, SO2, NO2, CO, O3 and NH3) 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 PM10 and PM2.5 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 PM10 and PM2.5 is as high as about 60% and 39% respectively. Among other pollutants, NO2 (−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. [Display omitted] •PM10 and PM2.5 concentrations reduced by about half in compare to the pre-lockdown•NO2 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