Assessment of Air Quality Changes in the Four Metropolitan Cities of India during COVID-19 Pandemic Lockdown

Abstract

In view of emerging threat of COVID-19 pandemic, stringent lockdown measures have been implemented in India since 25 th March, 2020. The present study aims to assess the changes in air quality before and during lockdown in the four major metropolitan cities of India viz., Delhi, Mumbai, Kolkata and Chennai. The data on major air quality parameters and meteorological parameters was collected for 15 days before lockdown (i.e., March 10 th-March 24 th , 2020) and 15 days after implementation of lockdown (25 th March-April 8 th , 2020). The lockdown measures reflected a significant reduction in air pollutants, most significant fall was estimated for NO 2 (29.3-74.4%) while the least reduction was noticed for SO 2. On the contrary, levels of ground level ozone were found to be increased (except in Mumbai), could be related to the lower utilization of O 3 owing to decrease of NO x in the environment. Since, the lockdown period has been extended, therefore further reduction of most pollutants is expected. Among the various metrological parameters, significant increase in diurnal temperature was observed at Delhi, Kolkata and Mumbai, however relative humidity has changed significantly only in Mumbai. In the absence of any major violent meteorological phenomena in India during recent months the significant difference in air quality parameters could be majorly attributed to the effect of lockdown measures. However, the regional differences may be because of the local emission of pollutants and the prevailing effects of secondary pollutants. These observations highlight the contribution of anthropogenic sources in air pollution, therefore, sustainable polices for mitigation of air pollution are essential in India.

Spatio-temporal analysis of air quality and its relationship with major COVID-19 hotspot places in India

“…The findings of this research are more or less similar with other studies where they performed short-term (a week/month) pre- and post-lockdown analysis in different ground air pollutants that were declined significantly over the Kolkata, Delhi, Mumbai and Chennai metro cities ( Singh and Chauhan, 2020 ; Bedi et al, 2020 ).…”

Bidirectional association between COVID-19 and the environment: A systematic review

“… Assess the changes in air quality parameters during the implementation of the lockdown measures in the four major metropolitan cities of India, viz., Delhi, Mumbai, Kolkata and Chennai for a one-month period (15 days before lockdown and 15 days after the implementation of lockdown). ( Bedi et al, 2020 ) 20–40% Decreased air pollution The space-based air quality measurements from the National Aeronautics and Space Administration (NASA) Ozone Monitoring Instrument (OMI) onboard the Aura satellite and the TROPOspheric Monitoring Instrument (TROPOMI) onboard the European Space Agency's (ESA) Sentinel-5 Precursor (Sentinel-5P) satellite were used for assessing the spatial and temporal evolution of tropospheric NO2 throughout California during the pre- and post-initiation of COVID-19 containment measures in the state. Investigate the impact of COVID-19 Containment Measures on Air Pollution in California Naeger and Murphy (2020) 30% Decreased air pollution Nitrogen dioxide (NO2) emission data obtained from Ozone Monitoring Instrument (OMI) on board the AURA satellite launched in 2004 as part of the NASA EOS (Earth Observation System) was used Compare the concentrations of atmospheric pollutants in the period before the lockdown and during the implementation of preventive control measures COVID-19.…”

“… Assess the changes in air quality parameters during the implementation of the lockdown measures in the four major metropolitan cities of India, viz., Delhi, Mumbai, Kolkata and Chennai for a one-month period (15 days before lockdown and 15 days after the implementation of lockdown). Bedi et al (2020) 48.9% Decreased air pollution Data were obtained from the platform: http://www.aqistudy.cn/ . Air Quality Index, Indicatory Air Pollutants and Impact of COVID-19 Event on the Air Quality near Central China Xu et al (2020a) Water Water quality decreased 15.9% of suspended particulate matter Improved water quality The suspended particulate matter was measured by the red band (655 nm) Investigate the effect of COVID-19 lockdown on surface water quality Yunus et al (2020) The BOD and COD values reduced by 42.83% and 39.25%, respectively, Faecal Coliform declined by over 40%.…”

Ambient air quality of a less industrialized region of India (Kerala) during the COVID-19 lockdown

“…Hence, the increase in the concentration of NH 3 in Kerala State during the LD 2020 indicates the contributions from the sources other than industrial and transportation sectors. On the other hand, the major urbanized/industrialized areas of India (e.g., Kolkata, Delhi, Chennai) observed a considerable reduction in NH 3 concentration due to the shutdown of transportation sector ( Bedi et al, 2020 ; Mahato et al, 2020 ). One may also note that K3 showed a significant reduction of NH 3 levels (-67 %) during the LD 2020, which could be attributed to the cessation of the industrial activities.…”