COVID-19 lockdown and its impact on tropospheric NO2 concentrations over India using satellite-based data

Abstract

The World Health Organization has declared the COVID-19 pandemic a global public health emergency. Many countries of the world, including India, closed their borders and imposed a nationwide lockdown. In India, the lockdown was declared on March 24 for 21 days (March 25-April 14, 2020) and was later extended until May 3, 2020. During the lockdown, all major anthropogenic activities, which contribute to atmospheric pollution (such as industries, vehicles, and businesses), were restricted. The current study examines the impact of the lockdown on tropospheric NO 2 concentrations. Satellite-based ozone monitoring instrument sensor data were analyzed in order to investigate the variations in tropospheric NO 2 concentrations. The results showed that from March 1 to 21, 2020, the average tropospheric NO 2 concentration was 214.4 Â10 13 molecule cm À2 over India, and it subsequently decreased by 12.1% over the next four weeks. An increase of 0.8% in tropospheric NO 2 concentrations was observed for the same period in 2019 and hence, the reduced tropospheric NO 2 concentrations can be attributed to restricted anthropogenic activities during the lockdown. In the absence of significant activities, the contribution of various sources was estimated, and the emissions from biomass burning were identified as a major source of tropospheric NO 2 during the lockdown. The findings of this study provide an opportunity to understand the mechanism of tropospheric NO 2 emissions over India, in order to improve air quality modeling and management strategies.

Spatio-temporal analysis of air quality and its relationship with major COVID-19 hotspot places in India

“…5 ). Our spatio-temporal findings about declined tropospheric NO 2 concentrations is well corroborate with other studies where the average short-term reductions were reported <12% post-lockdown in India ( Biswal et al, 2020 ; Naqvi et al, 2020 ).

Figure 5 The average tropospheric NO 2 concentration variations in the study area during a one-month pre- and post-lockdown period.

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Impact of COVID-19 lockdown on ambient air quality in megacities of India and implication for air pollution control strategies

“…During the lockdown period, this work and other recent studies highlighted the impact of restricted anthropogenic activities on air quality across India and other parts of the world (Sharma et al 2020;Jain and Sharma 2020;Mahato et al 2020;Dantas et al 2020;Chauhan and Singh 2020;Mor et al 2020). In India, particulate matter (PM 2.5 and PM 10 ) and NO 2 show a significant reduction of up to 40-50% in the many megacities during the lockdown period as highlighted by Jain and Sharma (2020), Mahato et al (2020), Singh et al (2020a), and Biswal et al (2020). The air quality index (AQI) improved by 15-44% in India's different parts (Sharma et al 2020).…”

COVID-19 lockdown induced changes in NO&lt;sub&gt;2&lt;/sub&gt; levels across India observed by multi-satellite and surface observations

“…The satellite-based studies by Biswal et al (2020) and Pathakoti et al (2020) estimated the change in NO2 levels using OMI observations whereas Siddiqui et al (2020) utilised TROPOMI to compute the change over eight major urban centres of India. Biswal et al (2020) reported that average OMI NO2 over India decreased by 12.7 %, 13.7 %, 15.9 %, and 6.1 % during the subsequent weeks of the lockdown. Similarly, Pathakoti et al (2020) reported a decrease of 17 % in average OMI NO2 over India as compared to the pre-lockdown period and a decrease of 18 % against the previous 5-year average.…”