Assessment of four urban forest as environmental indicator of air quality: a study in a brazilian megacity

Vehicular emissions comprise a main source of air pollutants, especially particulate matter (PM), which contains toxic compounds. Brazil has been restricting vehicular emissions for more than 30 years to minimize the impacts of fleet vehicles, but despite the restrictive legislation, several Brazilian cities still suffer from the effects of atmospheric pollution. The adoption of nature-based solutions (NbS) is being hailed as a sound alternative for improving urban air quality. In this sense, trees are a true reflection of the NbS concept since they can directly decrease PM levels by intercepting and resuspending particles, as well as altering pollution dispersion patterns. We wanted to understand the practical outcome of urban forest fragments as an NbS. Therefore, using litterfall in urban forest fragments, this study reported the role of green areas in reducing air pollution concentrations in 4 urban parks in Sao Paulo Megacity, Brazil. Air contaminants (Cd, Cu and Pb) varied from the edge to the core of urban forests. Multivariate analysis revealed that areas with different vehicle fleets influenced the input of air pollutants into these forest fragments. Our study further showed that trees serve as a natural barrier against PM. It can be concluded that this low-cost NbS alternative can reduce air pollution and has a potential to improve human health and well-being, and should be incorporated into municipal policies and programs, especially in critical locations of high human density. and poorly managed green areas.