A better understanding of air quality resulting from the effects of the 2020 pandemic in a city in the equatorial region (Fortaleza, Brazil).

The year 2020 was atypical due to the pandemic caused by the SARS-CoV-2 virus (COVID-19), providing a unique opportunity to understand changes in air quality due to the reduction in urban activity. Therefore, the aim of the present study was to perform an integrated evaluation on the influence of the effects of the 2020 pandemic on air quality in the city of Fortaleza, investigating levels of PM, PM, NO, NO, SO, CO, and O, corresponding health risks, as well as the influence of meteorological variables and urban activity. In all phases analyzed, significant reductions were found in NO, NO, NO, and CO. A considerable reduction in PM and PM was found in the early phases, with an increase in the later phases. These findings are explained by the nearly 50% reduction in vehicular traffic and the consequent reduction in fossil fuel emissions, mainly in the partial lockdown and total lockdown periods, as well as reductions in commercial (stores/shops) and industrial activities. The variation in O was initially non-significant, followed by a considerable increase in the last three phases analyzed; this increase was influenced by changes in temperature and the incidence of sunlight. SO concentrations increased in the period studied, demonstrating that the vehicular fleet, local commerce, and other activities are not the predominant sources of this compound. Estimated health risks were reduced by half during the lockdown period, especially for non-smokers, followed by a drastic increase in the last three phases. The planetary boundary layer was positively correlated with O and PM and negatively correlated with NO, NO, and NO, indicating its influence on the distribution of pollutants in the lower atmosphere and, consequently, air quality.