Carlos Roberto Appoloni

Mass attenuation coefficients of brazilian soils in the range 10–1450 keV

Abstract The mass attenuation coefficients of the LRd-A 3 Brazilian soil has been measured at seven energies in the range of 59.5–1408.0 keV. Radioactive isotopes were used as sources of monoenergetic γ radiation in a narrow-beam collimated geometry. Experimental errors were in the range from 0.4 to 3.1%. Also mass attenuation coefficients of six Brazilian soils have been calculated in the energy range from 10 keV to 10 GeV to study the influence of chemical composition. Comparison between data, theoretical calculated values and data from the literature has been done for the LRd-A 3 soil.

Portable XRF and principal component analysis for bill characterization in forensic science

Several modern techniques have been applied to prevent counterfeiting of money bills. The objective of this study was to demonstrate the potential of Portable X-ray Fluorescence (PXRF) technique and the multivariate analysis method of Principal Component Analysis (PCA) for classification of bills in order to use it in forensic science. Bills of Dollar, Euro and Real (Brazilian currency) were measured directly at different colored regions, without any previous preparation. Spectra interpretation allowed the identification of Ca, Ti, Fe, Cu, Sr, Y, Zr and Pb. PCA analysis separated the bills in three groups and subgroups among Brazilian currency. In conclusion, the samples were classified according to its origin identifying the elements responsible for differentiation and basic pigment composition. PXRF allied to multivariate discriminate methods is a promising technique for rapid and no destructive identification of false bills in forensic science.

Brazil nuts: determination of natural elements and aflatoxin

Um estudo foi realizado para avaliar a associacao dos niveis de radioatividade, selenio e aflatoxinas em castanha-do-Brasil descascada, que foram classificadas em diferentes tamanhos, para exportacao. As determinacoes de selenio foram realizadas por espectrometria de emissao optica com plasma indutivamente acoplado (LOQ=3,0 µg kg-1) e aflatoxinas foram detectadas por LC-MSMS (LOQ=0,85 µg kg-1), as taxas de recuperacao ficaram entre 92 e 100%. A radioatividade foi medida por espectrometria gama de alta resolucao. A concentracao media de selenio foi de (22,7 ± 7,4) µg g-1. (n = 30). A atividade media determinada para os radioisotopos foram: 15,77 Bq kg-1 para o 224Ra, 104,8 Bq kg-1 para 226Ra e 99,48 Bq kg-1 para 228Ra. Para 226Ra, os niveis nao variaram significativamente com o tamanho das nozes, embora tais diferencas foram observadas para 224Ra e 228Ra. Nao houve associacao estatisticamente significativa entre o nivel de selenio e a atividade de radionuclideos, no entanto, houve correlacao entre os radionuclideos. Nao foi encontrado aflatoxinas acima do limite de quantifcacao.A study was carried out to evaluate the association of levels of radioactivity, selenium and aflatoxin in shelled Brazil nuts, which were classified in different sizes, for export. The selenium determinations were performed by inductively coupled plasma optical emission spectrometry (LOQ = 3.0 µg g-1), and aflatoxins were detected by Liquid chromatography-mass spectrometry (LOQ = 0.85 µg kg-1), recovery rates were between 92 and 100%. Radioactivity was measured by high-resolution gamma spectrometry. The selenium mean concentration was (22.7 ± 7.4) µg g-1. (n = 30). Mean activities determined for the following radium isotopes were: 15.77 Bq kg-1 for 224Ra, 104.8 Bq kg-1 for 226Ra and 99.48 Bq kg-1 for 228Ra. For 226Ra, the levels did not vary significantly with nut sizes, although such differences were observed for 224Ra and 228Ra. There was no statistically significant association between the level of selenium and the activity of radionuclides, however, there was correlation between the radionuclides. Aflatoxins above the quantification limit were not found.

Two media method for gamma ray attenuation coefficient measurement of archaeological ceramic samples

This work reports the application of an alternative methodology for the linear attenuation coefficient determination of irregular shape samples, in such a way that it is not necessary to know the sample thickness. Based on this method, indigenous archaeological ceramic fragments from the region of Londrina, north of Parana State in Brazil, were studied. On the other hand, theoretical mass attenuation coefficient values were determined with the XCOM computer code. With the results obtained, it was concluded that the two media method works very well for the linear attenuation coefficient measurement of irregular-shaped ceramic samples, which makes it suitable, especially, for archaeometric studies.

Ceramic foams porous microstructure characterization by X-ray microtomography

Knowledge of the porous structure of amorphous materials is of fundamental importance in calculating geometrical parameters such as total porosity, pore size distribution and physical parameters relating to fluid flow inside void space. The present work deals with the measurement of the microstructural parameters of porous ceramic filters. Microtomographic measurements of samples were taken using an X-ray tube. Bremsstrahlung radiation was filtered in transmission mode with a Sn filter at 58.5 and 28.3 keV and the images analyzed in two ways. The first method consisted in analyzing transepts of the images in order to calculate total porosity based on the average particle size and media linear attenuation coefficients. The second method involved a study of the images using an image analysis software, called Imago, which allows one to calculate total porosity and pore size distribution. The total measured porosity of the filter C90 was 73.8%, 71.1%, 74.4% and 71.5% by, respectively, the Arquimedes method, simple gamma ray transmission, transept analysis and analysis of the microtomographic images at 28.3 keV.

Quantification of metals in river water using a portable EDXRFsystem

This work identified, quantified, and presents results for metals in water using a portable energy dispersive X-ray fluorescence (EDXRF) system. It was possible to quantify the following range of concentrations in mg L(-1): Ca(0.043-0.021), Ti(0.137-0.014), Mn(0.052-0.008), Fe(1.66-0.035), Ni(0.012-0.010), Cu(0.010-0.007), Zn(0.070-0.007), and Pb(1.01-0.85). The final conclusion is that in 4h of field work it was possible to prepare, measure, and analyze 14 membranes.

Effects of manual threshold setting on image analysis results of a sandstone sample structural characterization by X-ray microtomography.

Binarization process plays an important role in structural characterization by means of micro-CT images analysis. The choice of the correct threshold to separate porous phase from the material is the procedure for binary images creation. Slight variations of the threshold level led to substantial variations in physical parameters determination. The aim of this work is to evaluate these variations based on manual threshold settings data of five operators. Porosity and pore size distribution of a sandstone sample were determined.

Use of cesium-137 methodology in the evaluation of superficial erosive processes

Superficial erosion is one of the main soil degradation agents and erosion rates estimations for different edaphicclimate conditions for the conventional models, as USLE and RUSLE, are expensive and time-consuming. The use of cesium-137 antrophogenic radionuclide is a new methodology that has been much studied and its application in the erosion soil evaluation has grown in countries as USA, UK, Australia and others. A brief narration of this methodology is being presented, as the development of the equations utilized for the erosion rates quantification through the cesium-137 measurements. Two watersheds studied in Brazil have shown that the cesium-137 methodology was practicable and coherent with the survey in field for applications in erosion studies.

Soil erosion determination in a watershed from northern Paraná (Brazil) using 137Cs

The objective of this work was study the soil losses or gains in a watershed in the municipal district of Cambe, Parana using 137Cs as marker for the determination of soil redistributions. A transect sampling was used to evaluate the influence of different tillage on soil erosion. One point, located in a forest area was sampled and analyzed to determine the reference inventory of cesium-137 deposited by fallout. The average value of the reference inventory was 292 Bq m-2. The cesium-137 inventory of the transect samples varied from 80 Bq m-2 to 403 Bq m-2. The sampling points in pasture presented soil losses. The sampling points in coffee plantation did not present losses or gains. The sampling points in soybean cultivated areas presented soil losses.

Effective atomic number and density determination of rocks by X-ray microtomography

Microtomography, as a non-destructive technique, has become an important tool in studies of internal properties of materials. Recently, interest using this methodology in characterizing the samples with respect to their compositions, especially rocks, has grown. Two physical properties, density and effective atomic number, are important in determining the composition of rocks. In this work, six samples of materials with densities that varied from 2.42 to 6.84g/cm(3) and effective atomic numbers from 15.0 to 77.3 were studied. The measurements were made using a SkyScan-Bruker 1172 microtomography apparatus operating in voltages at 50, 60, 70, 80, 90 and 100kV with a resolution of 13.1μm. Through micro-CT images, an average gray scale was calculated for the samples and correlation studies of this value with the density and the effective atomic number of samples were made. Linear fits were obtained for each energy value. The obtained functions were tested with samples of Amazonite, Gabbro, Sandstone and Sodalite.