What Can We Learn about Improvements in Air Quality During the COVID-19 Pandemic? A Case Study in Four Cities Located in the Same State but with Different Emission Profiles

This study aimed to assess how a partial lockdown due to the coronavirus disease 2019 (COVID-19) pandemic affected air quality in four cities with dissimilar characteristics. In three cities, Araraquara (ARQ), Presidente Prudente (PPE), and Santos (STS), reductions in NO₂ concentrations were observed due to social distancing. Conversely, in Santa Gertrudes (SGD), NO₂ concentrations increased, indicating that a brief pause in ceramics industry activity was not sufficient to reduce NO₂ emissions. A variable behavior was observed in O₃ concentrations; in some cases, it followed the trends observed in previous years, but in others, an increase or decrease in concentrations was observed due to variations in concentrations of NO₂ and volatile organic compounds and/or climatic conditions. Particulate matter (PM) concentrations decreased in SGD and STS due to social distancing, meteorological conditions, such as wind speed, and reductions in industrial and port activities. Nevertheless, in the cities of ARQ and PPE, particulate matter with aerodynamic diameter ≤ 10 µm (PM₁₀) concentrations were elevated during the pandemic period, due to numerous biomass burning events in 2020. Thus, although vehicular and industrial emission control/reduction policies are effective in improving air quality, they may not be sufficient to achieve air quality standards if they are not combined with more restrictive measures to manage biomass burning.

Keywords:
air quality; nitrogen dioxide; ozone; particulate matter; coronavirus