Abstract: This work aims to characterize the chemical composition of PM2,5, using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), apportioning its sources and relation with the atmospheric conditions in the Metropolitan Area of Sao Paulo. Concentrations were monitored in the Faculdade de Saúde Pública (FSP; School of Public Health; 23o33’S, 46o40’W) from University of Sao Paulo, a region next to avenues and natural parks, from 05/09/2022 to 01/11/2023. After the sampling, the filters were cut in strips and stored in a freezer for preservation (Oliveira, 2020). The filters were digested and the resulting solution was filtrated, and the ICP-MS analysis was performed to obtain elemental concentrations. Principal Component Analysis (PCA) and Positive Matrix Factorization (PMF) model were applied for the identification of the PM2.5 sources. There were higher PM2.5 concentrations during winter, when temperatures and total rainfall were lower; the concentrations decreased in summer, along with an increase in temperatures and total rainfall. During the sampling period, air quality limit from CETESB (Sao Paulo Environmental Agency) was not exceeded, although there were 30 exceedances of the 24-h limit according to WHO (World Health Organization) guidelines. There were strong correlations between resuspension-related compounds and between vehicular-emitted compounds. The PCA as well as PMF results, suggested the following sources: heavy-duty and light-duty vehicles, road dust resuspension and civil construction. Particularly, vehicular emissions was the main source. The results were compared with another experimental campaign performed from 03/04/2019 to 01/01/2020 in the Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG; Institute of Astronomy, Geophysics and Atmospheric Sciences; 23,56oS, 46,74oW, approximately 6.2 km – 3.9 mi – from FSP). The compounds with the highest concentrations were the same at the two sites. PCA showed that the sources in IAG and FSP are distinguished by a biomass burning source on IAG, and the fact that the heavy- duty vehicle source is more important on FSP. Therefore, seasonal variations of PM2,5 coordinate with the expected function of meteorological conditions. The main sources of PM2,5 in the region of FSP are heavy-duty and light-duty vehicles, and road dust resuspension and civil construction, according to previous results for MASP.

Keywords: PM2,5, ICP-MS, PCA, PMF, Sao Paulo.