The present paper deals with the studies on the change in concentration of three standard pollutants namely, respiratory suspended particulate matter (RSPM or PM₁₀), Sulphur dioxide (SO₂) and Nitrogen dioxide (NO₂) because of lockdown in India to prevent the spread of COVID-19 pandemic in 2020. The monthlyaverage concentrations of the above pollutants observed at four monitoring stations in and around Nagpur city during January to December 2020 were analyzed and compared. Due to COVID-19 pandemic, there was a complete lockdown from 25th March to 31st May 2020 and phased reopening of areas outside containment zones from June 1st onwards. It is found that the average concentration of all the three pollutants at all four stations was reduced by about 50 % to 75 % due to lockdown. During lockdown, the minimum concentration of PM₁₀, SO₂ and NO₂ amongst all stations were found to be 40, 5 and 11 μg/m³, respectively, whereas the maximum concentrations were found to be 159, 20, and 50 μg/m³, respectively. The concentrations during lockdown were below the standards prescribed by CPCB, which were found to increase due to reopening. The Air quality index (AQI) at all four stations during lockdown was less than 50 (i.e. SATISFACTORY), whereas it increased above 100 (i.e. MODERATE) after reopening. As a result, the annual average concentration of pollutants was reduced in 2020 compared to previous years.

The present study deals with the analysis of daily average concentrations of respirable suspended particulate matter (RSPM- PM₁₀), sulfur dioxide (SO₂), and nitrogen dioxide (NO₂) at seven monitoring stations namely, Hazratganj, Talkatora, Mahanagar, Aliganj, Sarai Mali Khan, Gomtinagar, and Ansal TC in Lucknow city from 2016 to 2020. The analysis shows that the annual average concentration of RSPM varies from 148.74 to 323.05 μg/m³, SO2 varies from 7.11 to 8.94 μg/m³ and NO₂ from 23.52 to 31.86 μg/m³ at all the locations.From the analysis of seasonal variation, it is found that the minimum concentration of RSPM found to be 81.59 μg/m³ in monsoon and maximum concentration was found to be 447.47 μg/m³ in post-monsoon. However, the seasonal variation of SO2 was found in the range of 5.55 to 10.94 μg/m³ and NO₂ in the range of 20.23 to 38.40 μg/m³, which are below the prescribed standards. The pollution level decreased to some extent due to the COVID-19 lockdown in the year 2020 but not below the prescribed standard for RSPM. The levels of PM₁₀ in Lucknow are not reducing despite the government of India banning industries and adopting other safeguards within the city. The Trajectory and Dispersion study using the HYSPLIT4.0 model shows insufficient localpollution control, and pollutants are carried from adjacent locations due to the wind blowing from north-west direction to keep daily pollution levels over the standards prescribed by Central Pollution Control Board (i.e., 100 μg/m³). The peak concentration of RSPM is recorded to be 323.05 μg/m³ for the year 2017 at the Hazratganj monitoring station. Over the study region, wavelet analysis of monthly averaged values of PM₁₀ data sets at all seven stations revealed that the presence of semi-annual and annual periodicity. The findings revealthat controlling of particulate matter pollution in the city is a significant concern and has an alarming situation as compared to SO₂ and NO₂ pollutants.