Abstract
With the current COVID-19 pandemic being spread all over the world, lockdown measures are being implemented, making air pollution levels go down in several countries. In this context, the air quality changes in the highly populated and trafficked Brazilian states of São Paulo (SP) and Rio de Janeiro (RJ) were addressed using a combination of satellite and ground-based daily data analysis. We explored nitrogen dioxide (NO2) and fine particulate matter (PM2.5) daily levels for the month of May from 2015–2020. Daily measurements of NO2 column concentrations from the Ozone Monitoring Instrument (OMI) aboard NASA’s Aura satellite were analyzed and decreases of 42% and 49.6% were found for SP and RJ, respectively, during the year 2020 compared to the 2015–2019 average. Besides NO2 column retrievals, ground-based data measured by the Brazilian States Environmental Institutions were analyzed and correlated with satellite retrievals. Correlation coefficients between year-to-year changes in satellite column and ground-based concentrations were 77% and 53% in SP and RJ, respectively. Ground-based data showed 13.3% and 18.8% decrease in NO2 levels for SP and RJ, respectively, in 2020 compared to 2019. In SP, no significant change in PM2.5 was observed in 2020 compared to 2019. To further isolate the effect of emissions reduction due to the lockdown, meteorological data and number of wildfire hotspots were analyzed. NO2 concentrations showed negative and positive correlations with wind speed and temperature, respectively. PM2.5 concentration distributions suggested an influence by the wildfires in the southeast region of the country. Synergistic analyses of satellite retrievals, surface level concentrations, and weather data provide a more complete picture of changes to pollutant levels.
Highlights
The new coronavirus (COVID-19) disease was declared as a global pandemic by the World Health Organization on 11 March 2020 [1]
In Sao Paulo (SP), the range of NO2 column density values within the hydrographic region was 4.75 × 1015 molecules/cm2 (78.83 mol/km2) during both timeframes (May 2020 and May 2015–2019). This range for Rio de Janeiro (RJ) was 5.28 × 1015 molecules/cm2 (87.7 mol/km2) during 2015–2019, and 1.75 × 1015 molecules/cm2 (29 mol/km2) for 2020. These observations suggest that the partial lockdown had a more pronounced impact on the reduction of NO2 in RJ when compared to SP
Qualitative and quantitative differences in NO2 and PM2.5 concentrations were investigated for timeframes before and during the COVID-19 lockdown determined by the Brazilian government
Summary
The new coronavirus (COVID-19) disease was declared as a global pandemic by the World Health Organization on 11 March 2020 [1]. In Brazil, small towns to bigger cities and entire states have implemented lockdown regulations in varying periods and social-economic activities, depending on local virus propagation, infrastructure and regional characteristics [2]. The southeastern states of Sao Paulo (SP) and Rio de Janeiro (RJ) were the first ones to implement lockdown measures in local areas due to their high numbers of COVID-19 cases. Considering that they are highly populated and industrialized regions, and hold the largest economic clusters in the nation, any imposed changes on their regular activities greatly affects the country’s GDP (gross domestic product). On the other hand, were considerably reduced (e.g., a limitation of travel based on the plate number)
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