Short-term impacts of air pollutants in three megacities of India during COVID-19 lockdown

Abstract

Lockdown was imposed by the Indian government in the month of March 2020 as an early precaution to the COVID-19 pandemic which obstructed the socio-economic growth globally. The main aim of this study was to analyse the impact of lockdown (imposed in March and continued in April 2020) on the existing air quality in three megacities of India (Delhi, Mumbai and Kolkata) by assessing the trends of PM 10 and NO 2 concentrations. A comparison of the percentage reduction in concentrations of lockdown period with respect to same period in year 2019 and pre-lockdown period (February 14–March 24) was made. It was observed from the study that an overall decrease of pollutant concentrations was in the ranges of 30–60% and 52–80% of PM 10 and NO 2 , respectively, in the three cities during lockdown in comparison with previous year and pre-lockdown period . The overall decrease in concentrations of pollutants at urban sites was greater than the background sites. Highest decline in concentrations of PM 10 were observed in Kolkata city, followed by Mumbai and Delhi, while decline in NO 2 was highest in Mumbai. Results also highlighted that capital city Delhi had the worst air quality amongst three cities, with particulate matter (PM 10 ) being the dominant pollutant. Although COVID-19 has significantly affected the human life considering the mortality and morbidity, lockdowns imposed to control the pandemic had significantly improved the air quality in the selected study locations, although for the short amount of period.

Impact of COVID-19 Pandemic on Air Quality: A Systematic Review

“…Nevertheless, not all evidenced an increase of the pollutants after the lockdown, because of the slow economic recovery [ 48 , 61 , 70 ]. Similarly, studies that compared to the same period in previous years [ 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 ], and even more robustly with historical data of more than 5 years ( Table 1 ), reported a decrease of pollutants’ concentrations during the lockdown. As shown in Table 1 , decreases between 9–60%, 21.4–61.6%, and 30–66% were obtained for PM 2 .…”

PM2.5 concentration prediction during COVID-19 lockdown over Kolkata metropolitan city, India using MLR and ANN models

“…A recent study has been done to analyze the spatiotemporal variation of PM 10 and NO 2 over three megacities of India (Delhi, Mumbai and Kolkata). It has been observed that a significant reduction of pollutants has been registered over the megacities during lockdown period and the concentration level of PM 10 has significantly dropped over Kolkata metropolitan area mainly due to imposed of lockdown ( Ganguly et al., 2021 ). But the study has some limitations because the whole study has been conducted within a short time frame and in India, the air pollution parameters are not routinely updated or monitored.…”

Effect of COVID-19-induced lockdown on NO2 pollution using TROPOMI and ground-based CPCB observations in Delhi NCR, India

“…(Tobías et al, 2020) reported a 51% decrease in NO 2 in Barcelona and Spain during the two-week lockdown. Several other studies (Table 1) have indicated a reduction in NO 2 and other pollutants across Indian cities (Biswal et al, 2020;Biswas & Ayantika, 2021;Dumka et al, 2021;Ganguly et al, 2021;Jain & Sharma, 2020;Kumar et al, 2020b;Mahato et al, 2020;Navinya et al, 2020;Selvam et al, 2020;Sharma et al, 2020;Singh et al, 2020a, b) and other cities around the world as an effect of partial and complete lockdown (Acharya & Sreekesh, 2013). Studies indicated that ambient concentrations of pollutants were significantly curtailed as an after effect of the pandemic-related lockdown compared to before lockdown scenarios and last year status.…”