A.S. Paschoa

Analysis of trace elements in human hair by PIXE

Abstract The PIXE method was applied to the analysis of trace elements in scalp hair using two methods for target preparation. In the first method eight hair strands each of nearly circular cross-section and having approximately the same diameter were selected and placed on an aluminum frame. In the second method a given mass of hair was dissolved in nitric acid and a known amount of strontium was added to the solution and dripped onto a membrane filter using a micropipette. The results for the concentrations of trace elements in hair obtained by the two methods are compared and several aspects of the analysis are discussed.

Study of a proton beam diffusing system for pixe analysis

Abstract The experimental arrangement for uniformization and profile determination of the proton beam from the Van de Graaff accelerator at PUC/RJ is described and a discussion about the effects of the diffuser thickness and relative positron to the target on the beam uniformity is presented.

Uncertainties in elemental quantitative analysis by PIXE

Abstract The effects of the degree of non-uniformity of the particle beam, matrix composition and matrix thickness in a quantitative elemental analysis by particle induced X-ray emission (PIXE) are discussed and a criterion to evaluate the resulting degree of uncertainty in the mass determination by this method is established.

Size distribution of airborne particulates in monazite dust

Abstract A six-stage cascade impactor was used to collect airborne dust particulates in the grinding area of a monazite separation plant. The samples were analysed using particle-induced X-ray emission (PIXE) to determine the elemental concentrations, with special attention to thorium and uranium concentrations. The particle size distribution of the samples containing thorium and uranium were determined. The mass median aerodynamic diameter (MMAD) obtained was 1.15 μm for both elements. The activity median aerodynamic diameter (AMAD) was estimated based on the MMAD. The results are compared with ICRP recommendations for derived air concentrations (DAC) for thorium and uranium in restricted areas.

Graphical analysis of Rutherford backscattering spectra

A graphical method was developed to relate data from Rutherford backscattering spectrometry to sample characteristics, such as thickness and concentration profiles. The method was then applied to analyze these characteristics of a gold film.

A Critical Look at NORM In The Monazite Cycle

Thorium, cerium, lanthanum and other rare earths have been extracted from monazite sands for a long time due to several reasons. At the end of the XIX century monazite sands from Brazilian beaches were concentrated gravimetrically to be clandestinely transported to Europe to be used in the manufacture of fabric bags to be burned. Those bags when burning had their brightness enhanced by a mixture of thorium, lanthanum and cerium. The thorium oxide (ThO2) percentages found in monazite concentrates from several parts of the world range from 1 to 11%. While not burned or processed chemically monazite concentrate can be considered hazardous only due to gamma radiation and 220Rn (thoron) inhalation by those who stay very close to storage piles. In old monazite plants the thoron concentration in air reached levels higher than 20 kBq⋅m−3. Fortunately, the industrial hygiene improved with time and todays monazite separation plants do not present such high thoron concentrations. Old and recent data from rare earth...

EFFECTS OF X-RAY ABSORPTION IN THE ANALYSIS OF THICK TARGET SAMPLES BY XRF*

The accuracy of the quantitative analysis of thick targets by XRF is impaired by effects due to the absorption of X-rays in the matrix associated with the non-uniformity of the X-ray beam and the lack of knowledge of the actual distribution of trace elements in the target. The uncertainty in the elemental mass associated to a definite number X-rays detected is discussed in the paper. A correction factor is derived to account specifically for the effect of the absorption of X-rays and the non-uniformity of the X-ray beam.

Plants as Bio-monitor Agents: Foliar Deposition of Be-7, Pb-210, K-40 and Cs-137

Leaves of Eremanthus crotonoides, Allagoptera arenaria, Byrsonima sericea, Tibouchina sp, Tocoyena bullata and Clusia hilariana were collected under the same climatic in an area of restinga in the Northeast of the State of Rio de Janeiro, Brazil. The activity concentrations of selected radionuclides in the leaves samples were determined. The results obtained have shown a high concentration of 7Be and 40K in E. crotonoides, 210Pb in T. bullata and 137Cs in Tibouchina sp. The high activity concentration of 7Be in E. crotonoides can be explained by the presence of trichomes in the leaves. E. crotonoides and T. bullata reveal high foliar deposition of 7Be and 210Pb, respectively, thus these species can be used as bio‐monitors to evaluate the concentration and dispersion of radionuclides in environmental studies.

Human Exposure to Mineral Sands Dust Particles

Dust particles were generated during the separation process of mineral sands to obtain rutile, ilmenite, zircon and monazite concentrates. Aerosol samples were collected at the village and during the reprocessing phase of ilmenite. A cascade impactor with six stages was used to collect mineral dust particles with aerodynamic diameter in the range of 0.64 to 19.4 μm. Analyses of aerosol samples and lichen samples showed that the inhabitants of the Buena village were exposed to airborne particles in the fine fraction of aerosols. By employing the 252Cf‐PDMS technique the chemical compound of the elements found in the mineral dust particles samples, in the cerium oxide samples and in the concentrate of monazite samples were identified. The mass spectra (252Cf‐PDMS technique) of dust samples showed the presence of the thorium silicate, thorite and zircon in the fine fraction of aerosols. The 252Cf‐PDMS technique was, also, used to characterize urine sample from a inhabitant of the village. The results showed ...