No abstract

In this paper, we present in details a method for determining the soil density of disturbed samples. The mass attenuation coefficient was also evaluated by using the relation between the number of photon counts and the path length (soil density ×thickness). A typical student laboratory setup (PASCO) was utilized in the measurements. A gamma ray source of 137 Cs and soils with four different textural classes were employed. The experimental apparatus here proposed, that uses an educational gamma ray attenuation system, permitted measuring, with very good agreement with the traditional method, the density of soil samples. The experiment can be somehow extended by proposing the investigation of soil bulk variations due, for instance, to soil compaction, a subject of interest for engineering and environmental physics students.

Soils subjected to disaggregation can break into aggregates of different sizes composed of sand, clay, and silt particles. Each aggregate contains different oxides, which can vary according to the aggregate size and influence its properties, such as the radiation interaction parameters. These parameters are relevant in the evaluation of radiation shielding and soil physical properties. Thirteen tropical/subtropical soils of contrasting textures (clayey and loamy/sandy) with two aggregate sizes (2–1 mm and <45 μm) were studied. The radiation parameters analyzed were the atomic (σA), electronic (σE), and molecular (σM) cross-sections; the effective atomic number (Zeff); and the electron density (Nel). We verified that the aggregate sizes affected the major oxides (SiO2, Al2O3, Fe2O3). In general, the attenuation coefficient and Zeff were sensitive to the clayey soils’ aggregate sizes (low photon energies). However, the loamy/sandy soils did not exhibit differences among the parameters. As the photon energy increased, only Zeff presented differences for most soils. We also verified that σM, Zeff, and Nel were the most sensitive parameters to the soil composition. Although the soil chemical composition was influenced by the studied aggregate sizes, the radiation parameters exhibited differences for only some of these parameters. This means that the aggregate size is practically irrelevant when radiation parameters are determined based on X-ray fluorescence.

Abstract. Considering the importance to understand the behavior of the elements on different natural and/or anthropic processes, this study had as objective to verify the accuracy of a multielement analysis method for rocks characterization by using soil standards as calibration reference. An EDXRF equipment was used. The analyses were made on samples doped with known concentration of Mn, Zn, Rb, Sr and Zr, for the obtainment of the calibration curves, and on a certified rock sample to check the accuracy of the analytical curves. Then, a set of rock samples from Rio Bonito, located in Figueira city, Paraná State, Brazil, were analyzed. The concentration values obtained, in ppm, for Mn, Rb, Sr and Zr varied, respectively, from 175 to 1084, 7.4 to 268, 28 to 2247 and 15 to 761.

The objective of this study was to determine different radiation interaction parameters in clay soils, given the scarcity of works approaching this type of soil and its aggregation ability, which directly affects radiation attenuation. The parameters were theoretically determined through elemental analysis. The results showed that the parameters that presented a better distinction between soils were the effective atomic number (Zeff) and the molecular cross-section (σM). The Zeff, as well as the mass attenuation coefficient (μ/ρ) plus the atomic (σA) and the electronic (σE) cross-sections, presented strong positive correlations and direct relation with the soil Fe2O3 content. The σM, in turn, showed a negative correlation with the iron oxide content while presenting a strong positive correlation with the molecular weight of each soil constituent. Finally, the radiation interaction parameter set proposed in this study enabled the characterization of the soils regarding their chemical composition, even in soils with the same texture.