Assessment of air quality in Kolkata before and after COVID-19 lockdown
Suranjana Banerji, Deblina Mitra
Abstract
Air Pollution plagues urbanised areas and enhances mankind’s vulnerability to the COVID-19 virus. According to W.H.O, Kolkata (India) ranks 25<sup>th</sup> amongst 1100 cities in the world. Curbs on traffic movement reduced this pollution during COVID-19 lockdown. Resumption of activities nullified this. This study analyses the trend of air pollutants, their interrelationships with PM<sub>2.5,</sub> PM<sub>10</sub>, resultant National Air Quality Indices (NAQIs) before and after COVID-19 lockdowns in Kolkata. Temporal trend analysis, PCA, multiple regressions and NAQIs were computed using pollutant data. SO<sub>2</sub>, NO<sub>2</sub>, CO, NH<sub>3</sub>, PM<sub>10</sub> and PM<sub>2.5</sub> witnessed drastic rise and fall and again subsequent rise through the pre-lockdown to lockdown and unlock phases, respectively. NAQIs reduced by 74.55%, in the former phase, while in the next it reduced by 5.93%. PM<sub>10</sub> and PM<sub>2.5</sub>, <5µm in aerodynamic diameter, had positive associations with SO<sub>2</sub> and NO<sub>2</sub>, which stimulates air-borne transmission of COVID-19. Pollutant monitoring, bio-filtration, biofuel use may be adopted.