Estudo crítico de métodos de preparo de amostras de material particulado atmosférico para determinação de elementos-traço por espectrometria de absorção atômica

Abstract

On the atmosphere, particles of solids or liquids are found, suspended in the air, known as particulate matter. The size of these particles may be associated with their harmful potential to human health, since they can be retained in the respiratory tract, causing several diseases. Several contaminants, such as trace elements, can be found on the surface of particulate matters. In this context, the aim of this study was to develop analytical methods for extraction of trace elements from atmospheric particulate matter samples with subsequent determination of these elements by atomic absorption spectrometry. The samples were collected, monthly, in the city of Juiz de Fora, MG, Brazil, during 24 months, using passive samplers, installed at four sampling sites (two avenues with large fleet of vehicles, an industrial area and a region with high altitude and small fleet of vehicles). Instrumental parameters for the determination of Al, As, Cd, Cr, Cu, Fe, Mn, Pb and Zn by flame atomic absorption spectrometry (F AAS) and graphite furnace atomic absorption spectrometry (GF AAS) were investigated. Two sample preparation methods for particulate matters were developed, using ultrasonic assisted extraction and microwave assisted extraction. The methods showed adequate results regarding precision (RSD <10 %) and accuracy (recoveries between 83 and 114 %), with reduced time (10 min) in sample preparation and low reagent consumption (aqua regia: 5.0 mL). Particulate matter samples (n = 92) were prepared with microwave assisted extraction using diluted aqua regia, with subsequent determination of the analytes by F AAS and GF AAS. Using enrichment factor, principal component analysis, hierarchical cluster analysis and Pearson correlation, the possible sources of each analyte at each point were identified. The analytes Al, Fe, Cr and Mn were related to natural sources, such as the resuspension of soil dust. However, the analytes As, Cu, Cd, Pb and Zn may be associated with anthropogenic sources. Critical mean values were obtained for Cd, Pb and Zn (146, 2895, 40924 mg kg-1, respectively) at site 2, a region with intense industrial activity. In general, the possible sources of the analytes in the studied particulate matter samples are resuspension of soil dust, industrial emission (metallurgy and steel mill), biomass burning, building construction and fossil fuel emissions.