Variable impact of COVID-19 lockdown on air quality across 91 Indian cities

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  • 1 Department of Geography, Lalbaba College, University of Calcutta, Howrah, WB, 700202, India. Email: khanansargeo@gmail.com
  • | 2 Department of Geography, University of Calcutta, Kolkata, WB, 700019, India. Email: samirankhorat054@gmail.com
  • | 3 School of Oceanographic Studies, Jadavpur University, Kolkata, WB, 700 032, India. Email: rupaliocean@gmail.com
  • | 4 Centre for Computational Sciences, University of Tsukuba, Ibaraki, 3058577, Japan. Email: Doan.van.gb@u.tsukuba.ac.jp
  • | 5 Department of Atmospheric Sciences, University of Alabama in Huntsville, Huntsville, AL, 35806, USA. Email: nairu@uah.edu
  • | 6 Department of Geological Sciences, Jackson School of Geosciences, and Department of Civil, Architectural, and Environmental Engineering, The University of Texas at Austin, Austin, TX 78712, USA. Email: happy1@utexas.edu
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Abstract

India responded to the COVID-19 pandemic through a three-phase nationwide lockdown: 25 March - 14 April, 15 April - 3 May and 4 - 17 May, 2020. We utilized this unique opportunity to assess the impact of restrictions on the air quality of Indian cities. We conducted comprehensive statistical assessments for the Air Quality Index (AQI) and criteria pollutant concentrations for 91 cities during the lockdown phases to the preceding seven days (pre-lockdown phase 18-24March,2020) and corresponding values from the same days of the year in 2019. Both comparisons show statistically significant country-wide mean decrease in AQI (33%), PM2.5 (36%), PM10 (40%), NO2 (58%), O3 (5%), SO2 (25%), NH3(28%), and CO(60%). These reductions represent a background or the lower bound of air quality burden of industrial and transportation sectors. The northern region was most impacted by the first two phases of the lockdown, while the southern region was most affectedin the last phase. The northeastern region was least affected, followed by the eastern region which also showed an increase in O3during the lockdown. Analysis of satellite retrieved Aerosol Optical Depth (AOD) shows that effects of restrictions on particulate pollution to be variable- locally confined in some areas or having a broader impact in other regions. Anomalous behavior over the eastern region suggestsa differing role of regional societal response or meteorology. The study results have policy implications as they provide the observational background values for the industrial and transportation sector’s contribution to urban pollution.

Corresponding Author: Ansar Khan, Department of Geography, Lalbaba College, University of Calcutta, Howrah, WB, 700202, India. Email: khanansargeo@gmail.com

Abstract

India responded to the COVID-19 pandemic through a three-phase nationwide lockdown: 25 March - 14 April, 15 April - 3 May and 4 - 17 May, 2020. We utilized this unique opportunity to assess the impact of restrictions on the air quality of Indian cities. We conducted comprehensive statistical assessments for the Air Quality Index (AQI) and criteria pollutant concentrations for 91 cities during the lockdown phases to the preceding seven days (pre-lockdown phase 18-24March,2020) and corresponding values from the same days of the year in 2019. Both comparisons show statistically significant country-wide mean decrease in AQI (33%), PM2.5 (36%), PM10 (40%), NO2 (58%), O3 (5%), SO2 (25%), NH3(28%), and CO(60%). These reductions represent a background or the lower bound of air quality burden of industrial and transportation sectors. The northern region was most impacted by the first two phases of the lockdown, while the southern region was most affectedin the last phase. The northeastern region was least affected, followed by the eastern region which also showed an increase in O3during the lockdown. Analysis of satellite retrieved Aerosol Optical Depth (AOD) shows that effects of restrictions on particulate pollution to be variable- locally confined in some areas or having a broader impact in other regions. Anomalous behavior over the eastern region suggestsa differing role of regional societal response or meteorology. The study results have policy implications as they provide the observational background values for the industrial and transportation sector’s contribution to urban pollution.

Corresponding Author: Ansar Khan, Department of Geography, Lalbaba College, University of Calcutta, Howrah, WB, 700202, India. Email: khanansargeo@gmail.com
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