Did the COVID?19 lockdown in Delhi and Kolkata improve the ambient air quality of the two cities?

To control the spread of COVID-19, government India imposed a nationwide lockdown on all nonessential activities from 22 Mar. to 3 May 2020. Daily ambient particulate matter ?10 ?m in diameter (PM10), ?2.5 (PM2.5), NO, NO2, and O3 concentrations Delhi Kolkata 1 March both 2019 2020 were collected different monitoring stations along with meteorological data study impact COVID-19 pollutant concentrations. In 2020, average PM10 PM2.5 significantly decreased (Delhi: 59 43%, respectively; Kolkata: 49 50%, respectively) during period compared same cities. Average concentration was lower (38.5 ?g m–3) (44.7 period. However, higher (46.9 (31.4 Kolkata. Effect size analysis predictive variables reveals that explains maximum variation cities explained primarily by spatial rather than This suggests major policy implementation related transport industrial sectors aims address air pollution problem may reduce concentrations, although it not have significant effect other pollutants such as Indian