Study of the elemental composition of aerosols in the Candiota region of Brazil using the PIXE technique

摘要

The scope of this study was to determine the concentration and composition of atmospheric particles in the Candiota region of Brazil using HV PM_(10) and Dichotomous (PM_(10-2.5) and PM_(2.5)) samplers. Four sampling sites at an average distance of about 35 km from a coal-fired thermoelectric power plant were selected: Acegua, Aeroporto, 8 de Agosto and Pedras Altas. Samples were collected from December 2000 to December 2001, and their PM_(10) mass concentrations (coarse and fine particles) were determined. Moreover, the concentration of the elements Si, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and Br were obtained through the PIXE technique. The average mass concentrations of coarse and fine particles were found to be well below the daily (150 μgm~(-3)) and annual average (50 μgm~(-3)) air quality standards established by the country's legislation. The high enrichment factors observed in the fine fraction particulate (<2.5 μm) suggests that anthropogenic activities were the dominant source for elements such as S, V, Cr, Ni, Cu, Zn and Br. Analysis performed with HV PM_(10) samples showed a grouping of the elements Si, K, Ca, Ti, Mn and Fe, indicating coal and earth crust as the possible sources of these elements, whereas the presence of S is associated to coal combustion. The elements Cr, Ni and Cu characterise the influence of the power plant, while the presence of Cl and Br is associated with the presence of marine salts in the area.