Exploratory and comparative analysis of the morphology and chemical composition of PM2.5 from regions with different socioeconomic characteristics

Abstract

Chemical and physical properties of fine particulate matter (PM2.5) are related to emission sources. In order to determine chemical and physical differences, PM2.5 samples were collected at urban, rural and industrial areas of the metropolitan region of Rio de Janeiro (MRRJ), Brazil. The chemical characterization of the samples was performed using ion chromatography (IC) and inductively coupled plasma mass spectrometry (ICP-MS), while the physical characterization was done by scanning electron microscopy–energy dispersive spectrometry (SEM-EDS). Through the use the Hybrid Single-Particle Lagrangian Integrated Trajectories (HYSPLIT) model, it was observed that all the studied sites presented the influence of ocean air masses. The industrial and rural sites showed to influence of continental air masses too, that carried aerosols with greater UV absorption compared to those observed in trajectories originating in the Atlantic Ocean. Among analyzed species, NO3− and SO42− ions and V, Pb and Sn elements were predominant in the urban site whereas in the rural and industrial sites Na+, SO42− were the major ions and Na, Zn and Ba were the elements with the higher concentrations. Through SEM-EDS analysis, the particles were classified into two categories, the first in terms of the morphological similarities and the second in function of the elemental composition. As observed in ICP-MS analysis, the elements K, Al, Ca, Fe, Cu, Zn, Ba and Mg were detected also in the individual particles analysis by SEM-EDS. These results showed that C, O and Si were predominant elements at all sites. The morphological and chemical analyses indicate that the influence of vehicular emissions as a common source at all sites. The analyses also showed that the urban sites present particles with more diverse morphologies compared to rural and industrial sites.