Impact of COVID-19 Containment Measures on Air Pollution in California

Abstract

This study used space-and ground-based sensors in conjunction meteorological and traffic information to evaluate the impact of the COVID-19 containment measures on air pollution in California by comparing data from March-April 2020 to the similar period in 2019. Although significantly lower pollution levels were observed throughout the COVID-19 containment period in 2020 compared to 2019, our meteorological analysis found that periods of enhanced precipitation likely contributed to the cleaner environment over the Central Valley and southern California. Therefore, we focused our assessment on a 19-day period of drier conditions across the region. During this period, TROPOspheric Monitoring Instrument (TROPOMI) data revealed strong reductions in tropospheric NO 2 of 40% in Los Angeles, 38% in Fresno, and about 20% in Bakersfield and San Francisco when compared to 2019. The reductions were mostly within about 10% of the decrease in vehicle miles traveled (VMT), which indicates that the decrease in traffic-related NO x due to the COVID-19 lockdown was an important driver of the NO 2 reduction. Ozone Monitoring Instrument (OMI) data showed similar NO 2 reductions to TROPOMI over Los Angeles during the lockdown, but drastically different results over the other cities where little to no reductions were observed. The close agreement between ground-based and TROPOMI observations indicated that a more accurate assessment of the impacts from the COVID-19 lockdown can be accomplished using TROPOMI rather than OMI data, which is attributed to its improved resolution and sensitivity that can better characterize NO 2 pollution associated with fine-scale emissions. Altogether, the space-and ground-based observations provide strong evidence that the containment measures led to NO 2 reductions of around 35% in Los Angeles and Fresno and 25% in San Francisco and Bakersfield relative to 2019, along with decreases in PM 2.5 and improved air quality at the surface.

COVID-19 lockdown induced changes in NO<sub>2</sub> levels across India observed by multi-satellite and surface observations

“…A significant reduction in the range of ~25-75 % is observed, consistent in all observational sources used in this study. A similar reduction observed by the satellites over the cities in other parts of the world has been reported (Tobías et al, 2020;Naeger and Murphy, 2020;Kanniah et al, 2020;Huang and Sun, 2020). The satellites observe the largest reduction over Delhi and smallest over Kolkata.…”

Impacts of Traffic Reductions Associated With COVID‐19 on Southern California Air Quality

“…COVID‐19 traffic reductions led to an overall drop in atmospheric NO 2 concentrations in LA similar to those seen in other major cities around the world (Bauwens et al, 2020; Goldberg et al, 2020; Le et al, 2020; Naeger & Murphy, 2020; Tanzer‐Gruener et al, 2020). Depending on the location in the basin, afternoon NO 2 concentrations for 2020 were up to 33% lower than those expected using the trend between 2000 and 2019; in several remote locations, NO 2 levels were actually larger than expected in 2020 (Table S1).…”

“…The trends in afternoon O 3 concentrations vary in different parts of the basin, from decreases of 0.87% to increases of 0.64% per year, while afternoon O x concentrations have decreased by between 0.39% and 1.53% per year across the basin. COVID-19 traffic reductions led to an overall drop in atmospheric NO 2 concentrations in LA similar to those seen in other major cities around the world (Bauwens et al, 2020;Goldberg et al, 2020;Le et al, 2020;Naeger & Murphy, 2020;Tanzer-Gruener et al, 2020). Depending on the location in the basin, afternoon NO 2 concentrations for 2020 were up to 33% lower than those expected using the trend between 2000 and 2019; in several remote locations, NO 2 levels were actually larger than expected in 2020 (Table S1).…”

Bidirectional association between COVID-19 and the environment: A systematic review

“… ( Bedi et al, 2020 ) 20–40% Decreased air pollution The space-based air quality measurements from the National Aeronautics and Space Administration (NASA) Ozone Monitoring Instrument (OMI) onboard the Aura satellite and the TROPOspheric Monitoring Instrument (TROPOMI) onboard the European Space Agency's (ESA) Sentinel-5 Precursor (Sentinel-5P) satellite were used for assessing the spatial and temporal evolution of tropospheric NO2 throughout California during the pre- and post-initiation of COVID-19 containment measures in the state. Investigate the impact of COVID-19 Containment Measures on Air Pollution in California Naeger and Murphy (2020) 30% Decreased air pollution Nitrogen dioxide (NO2) emission data obtained from Ozone Monitoring Instrument (OMI) on board the AURA satellite launched in 2004 as part of the NASA EOS (Earth Observation System) was used Compare the concentrations of atmospheric pollutants in the period before the lockdown and during the implementation of preventive control measures COVID-19. By focusing on East China (Filonchyk et al) SO 2 Negligible Increased air pollution Data obtained from a network of air quality monitoring stations across 22 different cities in India for the past four years (2017–2020) for the time period of March 16th to April 14th.…”