Site 3—Jadavpur, Kolkata
After Delhi and Mumbai, Kolkata is the third populous metropolitan area in the nation. Kolkata is the educational, cultural, and commercial center of the eastern part of the country and is the capital of West Bengal. The concentration of PM2.5, PM10, NO2, NH3, SO2, and CO at site 3 significantly dropped steeply from 242, 205, 85, 10, 9, and 49 μg/m3 as on January 1, 2020 to 20, 28, 9, 1, 7, and 22 μg/m3 during COVID-19 pandemic confinement on May 31, 2020, respectively. Also, the mean concentration levels of PM2.5, PM10, NO2, NH3, SO2, and CO significantly reduced by 73%, 63%, 79%, 74%, 15%, and 32% due to decline in fossil fuel consumption, biomass burning, and other anthropogenic activities as observed from Fig. 4, while ozone levels were significantly raised by 77% with total variation of + 22 μg/m3 during confinement period as similar to Delhi due to high winds, intermittent rains and thunderstorms, and high temperature and heatwaves.