Characterization of sources of atmospheric particulate matter in urban and industrial environments of Rio de Janeiro by micro-XRF, SEM and PCA

Abstract Fine particulate matter (PM₂.₅) is one of the main atmospheric pollutants with significant implications for human health and the environment. In this study, PM₂.₅ samples were collected from different locations in the metropolitan region of Rio de Janeiro, covering urban and industrial areas. Particles were segregated into aerodynamic diameter ranges (0.12–2 μm) using a cascade impactor and characterized by micro X-ray fluorescence (micro-XRF) and scanning electron microscopy (SEM). Micro-XRF analyses identified the presence of the elements Al, Si, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, and Pb. Multivariate statistical methods, including Principal Component Analysis (PCA) and hierarchical cluster analysis (HCA), revealed distinct patterns of association among the elements. SEM micrographs showed particles with varied morphologies, including aggregated structures suggestive of black carbon, fine particulate agglomerates, and particles with features compatible with bioaerosols, such as pollen and insect fragments. These results highlight the chemical and morphological complexity of PM₂.₅ in urban and industrial environments and reinforce the importance of integrating analytical techniques for the characterization of atmospheric aerosols.