Impact of Nationwide COVID-19 Lockdown on Indian Air Quality in Terms of Aerosols as Observed from the Space

Manoj K Mishra,Pradyuman S Rathore

doi:10.4209/aaqr.2020.07.0461

Manoj K Mishra, Pradyuman S Rathore

Open Access

https://doi.org/10.4209/aaqr.2020.07.0461

Copy DOI

Abstract

Air pollution in India, especially in cities located in Indo-Gangetic plain (IGP), has exceeded all standards in the recent past. The development of an effective pollution control strategy requires knowledge of the pollutant sources, their spatio-temporal variability, and the efficacy of control strategies. The Indian government has implemented nationwide lockdown (LD) during March and April 2020 to contain the infectious disease COVID-19. LD also provides an opportunity to evaluate the efficacy of restricting anthropogenic activities in controlling air pollution. In the present paper, using data from space-borne sensors, a detailed analysis of the impact of LD on aerosols in the Indian atmosphere is presented. The aerosol optical depth (AOD), fine mode fraction (FMF), absorbing aerosol index (AAI), active fire/thermal anomaly and the HYSPLIT model is used to study the instantaneous state and spatio-temporal transportation of aerosols. On average, an overall decrease in AOD with 60% of the Indian landmass showing an average decrease of 0.16 is observed. A significant decrease in FMF indorses decreased AOD solely due to restricted anthropogenic activities, especially in IGP, which confirms the positive impact of LD on air quality. However, central, northeast and partially western India show some contrasting results which are associated with smoke from active fires. An increase of 30% in fire spots is observed during LD in these regions. The city-level analysis shows improved air quality in most of the cities located in IGP during LD. The cities located in the west, north-west and east India have shown a small decrease in AOD during LD, while in central, north-east, and few in the southern region, the increased AOD is observed in spite of LD due to increase in biomass burning.

Highlights

The COVID-19 pandemic forced the governments of different countries to shut down the industrial activity and transportation services
The major objectives of the present work are defined as (a) to study overall, regional and city-level variation of aerosol optical depth (AOD) and properties in India before and during LD period, (b) to do evidential study whether the observed trends in AOD are linked to LD or some other sources such as forest fire, and dust transportation, etc., (c) to serve knowledge about the sources that contribute to air pollution, their spatio-temporal variability, and the efficacy of restricting anthropogenic sources as a pollution control strategy in different parts of India
The increasing trend of AOD during the study period is the normal behavior of AOD as it is in agreement with the observations reported by Ramchandran et al (2008) where analysis of several years of MODIS-terra AOD product was carried out over the Indian region

Summary

Introduction

The COVID-19 (a disease caused by novel coronavirus 2019) pandemic forced the governments of different countries to shut down the industrial activity and transportation services. The impact of LD measure taken in other parts of the world such as countries in middle-east (Broomandi et al, 2020; Faridi et al, 2020; Sahin et al, 2020), South-Asia (Babu et al, 2020; Jain et al, 2020; Li et al, 2020; Metya et al, 2020; Navinya et al, 2020; Suhaimi et al, 2020), north and south-America (Naeger et al, 2020; Zalakeviciute et al, 2020) and Europe (Bessagnet et al, 2020; Tobias et al, 2020) to contain the spread of COVID-19 on air quality has been reported All these studies based on data acquired from space-borne as well as ground-based instruments endorses that LD measures taken to contain COVID-19. The major objectives of the present work are defined as (a) to study overall, regional and city-level variation of AOD and properties in India before and during LD period, (b) to do evidential study whether the observed trends in AOD are linked to LD or some other sources such as forest fire, and dust transportation, etc., (c) to serve knowledge about the sources that contribute to air pollution, their spatio-temporal variability, and the efficacy of restricting anthropogenic sources as a pollution control strategy in different parts of India

Objectives

Methods

Results

Conclusion