Impacts of nationwide lockdown due to COVID-19 outbreak on air quality in Bangladesh : a spatiotemporal analysis

In Bangladesh, a nationwide lockdown was imposed on 26 March 2020, due to the COVID-19 pandemic. Due to restricted emissions, it was hypothesized that the air quality has been improved during lockdown throughout the country. The study is intended to assess the impact of nationwide lockdown measures on air quality in Bangladesh. We analyzed satellite data for four different air pollutants (NO₂, SO₂, CO, and O₃) to assess the changes in the atmospheric concentrations of pollutants in major cities as well as across the country. In this study, the concentrations of NO₂, SO₂, CO, and O₃ from 1 February to 30 May of the year 2019 and 2020 were analyzed. The average SO₂ and NO₂ concentrations were decreased by 43 and 40%, respectively, while tropospheric O₃ were found to be increased with a maximum of > 7%. Among the major cities, Dhaka, Gazipur, Chattogram, and Narayanganj were found to be more influenced by the restricted emissions. In Dhaka, NO₂ and SO₂ concentrations were decreased approximately by 69 and 67%, respectively. Our analysis reveals that NO₂ concentrations are highly correlated with the regional COVID-19 cases (r = 0.74). The study concludes that the lockdown measures significantly reduced air pollution because of reduced vehicular and industrial emissions in Bangladesh.