Partial COVID-19 lockdown effect in atmospheric pollutants and indirect impact in UV radiation in Rio Grande do Sul, Brazil

The COVID-19 pandemic introduced a significant decrease in industrial activities and other anthropic interventions on the environment, followed by a reduction of the emission of pollutant gases and aerosols. Monitoring of air quality is commonly performed through automatic stations, which can provide nearly real-time, accurate information. However, stations located in urban areas are subject to maintenance problems and extensive coverage for large areas is not feasible. As an alternative approach, data from orbital sensors can provide useful information for large areas at a low cost. Consequently, this study aimed to analyze the partial COVID-19 lockdown effect in atmospheric pollutants and indirect impact in UV radiation in Rio Grande do Sul, Brazil. Data on concentrations of nitrogen dioxide (NO2), total ozone (O3), and ultraviolet index (UVI) acquired by the OMI sensor aboard the Aura satellite were accessed for May, for the entire period 2010 to 2018, 2019, and 2020. Differences between these time series were calculated. Results showed significant reductions in nitrogen dioxide in most of the study area by as much as 33.9%, followed by increases in total ozone of up to 3.5% and the ultraviolet index by up to 4.8%. Although NO2 plays a fundamental role in stratospheric chemistry, our results suggest that its decrease in 2020 was not directly responsible for the increase in total O3; however, NO2 was partially the cause for the increase in UVI, which in turn led to the heating of the stratosphere, generating an increase in ozone.