**Abstract**

The giant increase in COVID-19 infection across India forced the government to impose strict lockdown in order to curb the pandemic. Although the stringent restrictions crippled India's economy and poor people's livelihood, it significantly improved the air quality of most of the polluted cities of India and rejuvenated the atmosphere. Thus, the major objective of this study is to provide a comprehensive overview of lockdown on pollutants prevailing in the atmosphere. A prominent decline in primary pollutants such as Particulate matter (PM), Black carbon (BC), Oxides of nitrogen (NOx), Carbon monoxide (CO) is observed across the country. However, lockdown had a trifling impact on Sulphur dioxide (SO2) concentration over some parts of India due to the constant operation of coal-fired thermal plants as a part of essential service. Furthermore, the sudden decline in NOx concentration disturbed the complex atmospheric chemistry and lead to an enhancement of surface ozone (O3) (secondary pollutant) in many cities of India. Thus, lockdown emerged as a unique opportunity for the atmospheric researchers, policymakers as well as stakeholders to collect baseline data of pollutants and their major sources. This will help to set new targets of air quality standards and to develop various mitigation processes to combat air pollution.

**Keywords:** COVID-19, lockdown, aerosols, trace gas, air quality index
