Atmospheric Pollution Reduction in São Paulo City and the Social Isolation Effect

Abstract

Since January 2020, some studies have been reporting a reduction in air pollution in several countries due to social isolation measures, which have been adopted in order to contain the coronavirus outbreak progress (Covid-19). This study aims to evaluate the change in the atmospheric pollution levels by NO and NO2 in São Paulo city in the social isolation period. The NO and NO2 hourly concentrations were obtained through air quality monitoring stations from CETESB, from January 14 to April 12, 2020. Mann-Kendall and the Pettitt tests were performed in the air pollutants time series. We observed an overall negative trend in all stations, indicating a decreasing temporal pattern in concentrations. Regarding NO, the highest decrease rates were observed in Congonhas (-6.39 µg.m-3month-1) and Marginal Tietê (-6.19 µg.m-3month-1) stations; regarding NO2, the highest rates were observed in Marginal Tietê (-4.45 µg.m-3month-1) and Cerqueira César (-4.34 µg.m-3month-1) stations. In addition, we identified a turning point in the NO and NO2 series trends that occurred close to the start date of the social isolation period (March 20, 2020). Moreover, from statistical analysis, it was found that NO2 is a suitable surrogate for monitoring economic activities during social isolation period. Thus, we concluded that social isolation measures implemented in March 20, 2020 caused significant changes in the air pollutants concentrations in São Paulo city (as high as -200% in NO2 levels).