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. 2022 May:6:100078.
doi: 10.1016/j.hazadv.2022.100078. Epub 2022 Apr 20.

Comprehensive analysis of ambient air quality during second lockdown in national capital territory of Delhi

Gautam Kumar Sharma  1 , Ankush Tewani  1 , Prashant Gargava  1
Affiliations

Comprehensive analysis of ambient air quality during second lockdown in national capital territory of Delhi

Gautam Kumar Sharma et al. J Hazard Mater Adv. 2022 May.

Abstract

The lockdown imposed in Delhi, due to the second wave of the COVID-19 pandemic has led to significant gains in air quality. Under the lockdown, restrictions were imposed on movement of people, operation of industrial establishments and hospitality sector amongst others. In the study, Air Quality Index and concentration trends of six pollutants, i.e. PM2.5, PM10, NO2, SO2, CO, and O3 were analysed for National Capital Territory of Delhi, India for three periods in 2021 (pre-lockdown: 15 March to 16 April 2021, lockdown: 17 April to 31 May 2021 and post-lockdown: 01 June to 30 June). Data for corresponding periods in 2018-2020 was also analysed. Lockdown period saw 6 days in satisfactory AQI category as against 0 days in the same category during the pre-lockdown period. Average PM2.5, PM10, NO2 and SO2 concentrations reduced by 22%, 31%, 25% and 28% respectively during lockdown phase as compared to pre-lockdown phase, while O3 was seen to increase. Variation in meteorological parameters and correlation of pollutants has also been examined. The significant improvement arising due to curtailment of certain activities in the lockdown period indicates the importance of local emission control, and helps improve the understanding of the dynamics of air pollution, thus highlighting policy areas to regulatory bodies for effective control of air pollution.

Keywords: Air pollution; Air quality index; COVID-19 second wave; Criteria pollutants; Hybrid single-particle lagrangian integrated trajectory model; Meteorology.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Image, graphical abstract
Graphical abstract
Fig 1
Fig. 1
Location of CAAQMS in Delhi.
Fig 2
Fig. 2
Daily average temperature (Temp in ºC), Relative Humidity (RH in%) and rainfall (in mm) during study period of 2021.
Fig 3
Fig. 3
(a) Wind rose for pre-lockdown period 2021, (b) Wind rose for during lockdown period 2021, (c) Wind rose for post-lockdown period 2021 Note: Wind speed in m/s.
Fig 4
Fig. 4
Violin plot for AQI in Delhi for 2018–2021 under the three phases.
Fig 5
Fig. 5
Violin plots during the three phases in 2018–2021 for pollutants (a) PM2.5, (b) PM10, (c) NO2, (d) SO2, (e) CO, and (f)O3.
Fig 6
Fig. 6
Box plot depicting PM2.5/PM10 ratio for the three phases during 2021.
Fig 7
Fig. 7
Backward trajectories ending at 12 UTC on 26 April 2021 with source location at New Delhi.
Fig 8
Fig. 8
Backward trajectories ending at 23 UTC on 22 May 2021 with source location at New Delhi.
See this image and copyright information in PMC

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