Comprehensive study on impact assessment of lockdown on overall ambient air quality amid COVID-19 in Delhi and its NCR, India

• Published in: Journal of hazardous materials letters 2021-11, Vol.2, p.100010-100010, Article 100010
• Main Authors: Garg, Anchal, Kumar, Arvind, Gupta, N.C.
• Format: Article
• Language: English
• Subjects: Air quality index; Ambient air; COVID-19; Human health; Lockdown; Meteorology; Ozone
• ISSN: 2666-9110; 2666-9110
• DOI: 10.1016/j.hazl.2020.100010

[Display omitted] •Overall AQI of Delhi NCR region improved by 58 % and came under satisfactory level during lockdown.•PM10 and PM2.5 levels decreased upto 55–65 %.•NO and NOx concentration have shown maximum reduction (∼ 50–78 %).•Consistent and significant reduction observed in other pollutants such as SO2, CO, NH3 and C6H6.•An interesting feature observed that during first week of lockdown O3 decreased but later it increased by ∼19−27%. Indian government announced the complete lockdown from 25 March, 2020 for all outdoor activities across the country due to containment of COVID-19. This study is an attempt to assess the impacts of lockdown on ambient air quality in five cities of Indian National Capital Region including Delhi, Gurugram, Noida, Ghaziabad and Faridabad. In this context, the data of air pollutants (PM10, PM2.5, NOx, NO, NO2, SO2, NH3, SO2, CO, and C6H6) from 36 locations of the study area were analyzed from 1st March to 1st May, 2020. The results showed that PM10 and PM2.5 level decreased upto 55–65 %. NOx and NO have shown maximum reduction (∼ 50–78 %). Similarly, consistent and significant reduction in other air pollutants such as SO2 (∼33 %), CO (∼45 %), NH3 (∼27 %) and C6H6 (∼53 %) has been observed. During lockdown Air Quality Index (AQI) shows improvement as its value significantly decreased (∼ 45 %–68 %). An interesting feature observed that during first week of lockdown O3 decreased but later it increased by ∼19−27%. The study suggests that this pandemic gives lessons for interventions for urban air pollution mitigation in controlling the health impact due to urban air pollution.