Rodrigo O. Bastos

Granulometry and Moisture Influence for In Situ Soil Analysis by Portable EDXRF

The objective of this work was to verify the granulometry and the moisture influence in results when soils samples are measured for identification and quantification of metal, on field, employing portable Energy Dispersive X‐Ray Fluorescence (PXRF) equipment. For granulometry, the obtained concentration values for Ti, Fe and Zr, are equivalent for the samples grinded for one minute and the samples grinded and sieved. This result indicates that, for in situ analysis of this soil, it is sufficient to grind the dried sample before measurement. For moisture, concentration values obtained for the samples dried from 30 to 120 minutes at sun are equivalent. On the other hand, the concentration values obtained for the samples dried during 24 h are higher than the values obtained for the same samples dried at sun. Moisture influences the concentrations values in around 20%.

X-ray fluorescence and gamma-ray spectrometry combined with multivariate analysis for topographic studies in agricultural soil.

Physical and chemical properties of soils play a major role in the evaluation of different geochemical signature, soil quality, discrimination of land use type, soil provenance and soil degradation. The objectives of the present study are the soil elemental characterization and soil differentiation in topographic sequence and depth, using Energy Dispersive X-Ray Fluorescence (EDXRF) as well as gamma-ray spectrometry data combined with Principal Component Analysis (PCA). The study area is an agricultural region of Boa Vista catchment which is located at Guamiranga municipality, Brazil. PCA analysis was performed with four different data sets: spectral data from EDXRF, spectral data from gamma-ray spectrometry, concentration values from EDXRF measurements and concentration values from gamma-ray spectrometry. All PCAs showed similar results, confirmed by hierarchical cluster analysis, allowing the data grouping into top, bottom and riparian zone samples, i.e. the samples were separated due to its landscape position. The two hillslopes present the same behavior independent of the land use history. There are distinctive and characteristic patterns in the analyzed soil. The methodologies presented are promising and could be used to infer significant information about the region to be studied.

Gamma Radiation Dose Rate in Air due to Terrestrial Radionuclides in Southern Brazil: Synthesis by Geological Units and Lithotypes Covered by the Serra do Mar Sul Aero- Geophysical Project

The absorbed dose rates in air due to terrestrial radionuclides were estimated from aerial gamma spectrometric data for an area of 48,600 km2 in Southern Brazil. The source data was the Serra do Mar Sul Aero‐Geophysical Project back‐calibrated in a cooperative work among the Geological Survey of Brazil, the Geological Survey of Canada, and Paterson, Grant & Watson Ltd. The concentrations of eU (ppm), eTh (ppm) and K (%) were converted to dose rates in air (nGy⋅h−1) by accounting for the contribution of each elements concentration. Regional variation was interpreted according to lithotypes and a synthesis was performed according to the basic geological units present in the area. Higher values of total dose were estimated for felsic igneous and metamorphic rocks, with average values varying up to 119±24 nGy⋅h−1, obtained by Anitapolis syenite body. Sedimentary, metasedimentary and metamafic rocks presented the lower dose levels, and some beach deposits reached the lowest average total dose, 18.5±8.2 nGy⋅h−...

Energy dispersive X-ray fluorescence (EDXRF) equipment calibration for multielement analysis of soil and rock samples

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, Parana 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.

Radioactivity of a Rock Profile from Rio do Rasto Formation Measured by High Resolution Gamma Spectrometry

Natural occurring radionuclides are present in different concentrations in sedimentary rocks. Generally, their distribution correlates reasonably with their geo‐physicochemical behavior during sediment deposition and rock consolidation. This fact permits to study some geological characteristics of the rocks by analyzing the radionuclide distribution in the rocks, as it might reflect the origin of the sediments, the depositional environment, and more recent events such as weathering and erosion. In this work, rocks from an exposed profile of the Rio do Rasto Formation were collected and analyzed in laboratory by high resolution gamma spectrometry for 226Ra, 232Th and 40K determination. It was employed a standard gamma ray spectrometry electronic chain, with a 66% relative efficiency HPGe detector. The efficiency calibration, as well as its validation, was accomplished with eight International Atomic Energy Agency certified samples. The outcrop exposes layers of sandstone and siltstone and, secondarily, cla...

Some geological characteristics in a regolith-limey shale rock profile through natural radionuclides distribution

The objective of this work is to study some geological characteristics in a regolith-rock profile by analyzing the distribution of natural radionuclides along the profile by high resolution gamma ray spectrometry. The concentrations of radionuclides reflect some mineralogical characteristics of the rock matrix and also more recent events, such as weathering and erosion. The samples were collected in an abandoned limestone mine, in the city of Sapopema, Paraná State, Brazil. The stratigraphy is represented by an alternation of decimetric limestone layers, bituminous shale and some rhythmite layers. The ratios eTh/K obtained for all samples of the studied profile have equivalent values, indicating similar mineralogical characteristics of their detritic components. The ratio eTh/eU corroborates the fact that regolith samples belong to a much more oxidized environment, favoring the leaching of uranium. These results show that the measurement of radionuclide distribution in rocks and soils may be an important tool for the analysis of geological characteristics, such as mineralogy and oxidizing conditions.

Vertical Profiles Of 226Ra, 232Th And 40K Activities In Rocks From The Irati Formation Of The Paraná Sedimentary Basin, Southern Brazil

Naturally occurring radioisotopes are present in different concentrations in sedimentary rocks, reflecting the origin of the sediments, the depositional environment, and more recent events such as weathering and erosion. Using a high‐resolution γ‐ray spectrometry methodology, sedimentary rocks were measured to assess the concentration activities of the natural radioisotopes. The surveyed rocks are from the Irati formation in the Parana sedimentary basin, which are exposed by an abandoned, open‐pit limestone mine, in the city of Sapopema, southern Brazil. The exposed vertical profile is 5 m, and its stratigraphy is represented by an alternation of limestone and bituminous shale (layers being a few decimeters thick), and some millimeter rhythm layers with limestone and bituminous shale laminas. Eleven samples were collected along this profile, each of them dried in the open air during 48 hours, sieved through 4 mm mesh and sealed in cylindrical recipients. Measurements were accomplished using a 66% relative...

Modeling Background Attenuation by Sample Matrix in Gamma Spectrometric Analyses

In laboratory gamma spectrometric analyses, the procedures for estimating background usually overestimate it. If an empty container similar to that used to hold samples is measured, it does not consider the background attenuation by sample matrix. If a “blank” sample is measured, the hypothesis that this sample will be free of radionuclides is generally not true. The activity of this “blank” sample is frequently sufficient to mask or to overwhelm the effect of attenuation so that the background remains overestimated. In order to overcome this problem, a model was developed to obtain the attenuated background from the spectrum acquired with the empty container. Beyond reasonable hypotheses, the model presumes the knowledge of the linear attenuation coefficient of the samples and its dependence on photon energy and samples densities. An evaluation of the effects of this model on the Lowest Limit of Detection (LLD) is presented for geological samples placed in cylindrical containers that completely cover the...