COVID-19 Pandemic and Urban Air Quality: Delhi Region

Abstract

AbstractCOVID-19 pandemic hit the world bringing socio-economic and cultural shutdown of activities. The curse was a blessing to the environment in terms of significant air quality improvements. The study uses geospatial technology for assessing the reduction in nitrogen dioxide (NO2) levels and aerosol optical depth (AOD) levels using satellite-based (Sentinel-5P TROPOMI and MODIS data, respectively) and ground-based (Central Pollution Control Board, etc.) observations of 2019 and 2020. The study examines the lockdown period-wise reductions in ambient air pollution in the Delhi Region- the capital of India. It was investigated that satellite observations recorded a reduction of 51% in NO2 during lockdown phase-1 as compared to the pre-lockdown phase in 2020. When compared with 2019, the maximum reduction of 66.5% was seen in the lockdown phase-1, with p < 0.001. The ground-based stations also showed a 61% reduction in daily NO2 during lockdown phase-1 and phase-2 as compared to 2019. There is a drop in AOD by 55, 24 and 30% in lockdown phase-1, lockdown phase-2 and lockdown phase-3 w.r.t. pre-lockdown phases. However, an increase of 30% is observed during the post-lockdown phase of 2020 w.r.t. pre-lockdown phase. Ground-based stations ascertained that the reduction of 66, 60, 53 and 14% was observed in 2020 in the lockdown phases 1, 2 and 3 and post-lockdown phase w.r.t. pre-lockdown phase of 2020. Additionally, there is a 14, 56, 41, 39 and 3% reduction during the pre-lockdown, lockdown 1, lockdown 2, lockdown 3 and post-lockdown phase of 2020 w.r.t. similar periods of 2019. It was highlighted that environmental degradation can be mitigated with such stringent measures by policymakers from time to time to protect the deteriorating environment.KeywordsCOVID-19Geospatial technologyRemote sensingNO2AODPM2.5TROPOMICPCB