Air pollution in three megacities of India during the Diwali festival amidst COVID-19 pandemic

The present study characterized the difference in air pollution levels between Diwali celebrations amidst the Covid-19 pandemic (14 November 2020) and the previous year (27 October 2019). The concentration of seven principal air pollutants, namely PM2.5, PM10, NO2, NH3, SO2, CO, and O3, was substantially higher in 2020 Diwali than in 2019 Diwali. PM2.5, PM10, and CO were always above the permissible limits in all three megacities, with the highest concentrations observed in Delhi. This observation indicates that amidst the pandemic, people burnt more firecrackers than the preceding year. However, the pre-Diwali to Diwali changes in pollutant concentrations suggested that Mumbai and Kolkata had lower pollution levels due to the fireworks. The fireworkinduced air pollutant load in Delhi was enhanced by a higher margin in the pandemic year. The difference in meteorological conditions between the two consecutive year's Diwali might have led to the enhanced pollutant load in 2020, especially in Delhi. Delhi showed a tendency to retain the pollutants in the ground-level atmosphere for almost one week after the event. Thus, this study implies the need for stringent law enforcement to ameliorate the pollution levels due to such celebrations.