Propriedades de atenuação da radiação: influência da textura e tamanho de agregado do solo

Abstract

This study analysed 25 soil samples from the State of Paraná, Brazil, with different textures. Aiming at evaluating the parameters of radiation interaction with the matter, the samples were submitted to the semi-quantitative analysis using energy dispersive X-ray (XRF) fluorescence, to obtain the content of oxides contained in the soil mixture. Two particle sizes were analysed, being: the 45 μm, wich is the standard required by the manufacturer of the X-ray fluorescence equipment, and the 2-1mm. The oxide content, mass attenuation coefficient (𝜇𝜌⁄), molecular cross section (𝜎𝑀), atomic cross section (𝜎𝐴), electronic cross section (𝜎𝐸), effective atomic number (𝑍𝑒𝑓𝑓) and the electronic density (𝑁𝑒𝑙) were analysed in the 25 samples and for the two particle sizes. The results showed differences in the soil oxide content between one aggregate size and the other, revealing changes in the percentage of the Al2O3, SiO2 and Fe2O3 oxides. With the difference observed, there was change in the values of other parameters under analysis, the cross sections, the effective atomic number and the electronic density. The molecular cross section and the effective electronic density showed dependence on the content of Al2O3 and SiO2 oxides, which were found in higher percentages in sandy and loam soils, for both aggregate sizes. The atomic cross section was seen to present dependence on the total number of molecular formula units contained in the soil composition. While the remaining parameters, mass attenuation coefficient, electronic cross sections and the effective atomic number showed dependence on the Fe2O3 oxide, whose higher contents were found in the clay textured samples, for both aggregate sizes. In this way, it was observed texture and size dependency, both with the elementary chemical composition because in the first case, different textures are related to elementary and mineral composition in the different soils and the second due to the conformation of the aggregated in both analyzed arrays.