Impact of Lockdown on Air Pollutant Variation in Metropolitan Cities

Abstract

In early 2020, the COVID-19 pandemic swept the globe. In many countries, the complete lockdown resulting from the COVID-19 outbreak helped improve air quality, particularly in developing countries such as India. The main aim of the study is to assess the variation in AOD and various atmospheric pollutants such as PM_2.5, PM₁₀, NO₂, SO2, and O₃ before and after the lockdown. The data source used for the current study includes MODIS-Aqua, OMI, and ground-based monitoring data gathered from Central Pollution Control Board (CPCB). Time-averaged maps of Aerosol Optical Depth (AOD) at 500 nm, daily 1° [OMI OMAERUVd v003], and at 550 nm (Deep Blue, Land-only) daily 1° [MODIS-Aqua MYD08_D3 v6.1] were plotted on NASA’s Giovanni during 2010–2020. The data was extracted during the lockdown phases in India from March 25, 2020, to May 17, 2020. During the same period, changes in mean AOD were assessed during 2010–2019. Significant reductions were observed in mean AODs. Similarly, changes in the concentration of other pollutants were observed in the study areas during COVID. Fluctuations in the contaminants have also resulted from changes in meteorological conditions; hence, the impact of wind speed, temperature, and humidity are also studied on changing pollutant concentrations. This is owing to a reduction in local emissions resulting from anthropogenic activities due to the pandemic-control lockdown procedures. This work aids in visualizing pollutant responses in metropolitan cities as a result of reduced anthropogenic emissions, which can aid in developing atmospheric governance strategies.