  Air pollution has been on continuous rise with increase in industrialization
in metropolitan cities of the world. Several measures including strict climate
laws and reduction in the number of vehicles were implemented by several
nations. The COVID-19 pandemic provided a great opportunity to understand the
daily human activities effect on air pollution. Majority nations restricted
industrial activities and vehicular traffic to a large extent as a measure to
restrict COVID-19 spread. In this paper, we analyzed the impact of such
COVID19-induced lockdown on the air quality of the city of New Delhi, India. We
analyzed the average concentration of common gaseous pollutants viz. sulfur
dioxide (SO$_2$), ozone (O$_3$), nitrogen dioxide (NO$_2$), and carbon monoxide
(CO). These concentrations were obtained from the tropospheric column of
Sentinel-5P (an earth observation satellite of European Space Agency) data. We
observed that the city observed a significant drop in the level of atmospheric
pollutant's concentration for all the major pollutants as a result of strict
lockdown measures. Such findings are also validated with pollutant data
obtained from ground-based monitoring stations. We observed that near-surface
pollutant concentration dropped significantly by 50% for PM$_{2.5}$, 71.9% for
NO$_2$, and 88% for CO, after the lockdown period. Such studies would pave the
path for implementing future air pollution control measures by
environmentalists.
