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  • Author or Editor: E. Cortés x
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Abstract  

Instrumental neutron activation analysis of eight geochemical standard materials has been carried-out and the concentration values of nine rare-earth elements (REE) (La, Ce, Nd, Sm, Eu, Gd, Tb, Yb and Lu) have been determined. Discussion of some problems in the determination of those elements is presented and the results obtained are compared with literature values. In general, good agreement with available data was obtained but discrepancies with concentration values for a number of elements in some of these standards are discussed.

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Abstract  

A project has been undertaken to carry out a long term study on atmospheric air pollution in Chile using biomonitors. Samples of different species of lichens were collected in clean areas (native forest), analyzed and transplanted to the Santiago Metropolitan Area. In addition, samples of Tillandsia recurvata were collected in the Metropolitan Area for comparison purposes. The preparation of the samples was done under controlled, cryogenic conditions and analyzed by neutron activation analysis and solid sampling atomic absorption spectrometry. As part of the routine QA/QC procedures, the analytical laboratories, have participated in intercomparison runs organized by the IAEA for the determination of trace and minor elements in two lichens samples. The present paper describes the activities carried out within the framework of this project.

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Abstract  

Neutron activation analysis (NAA), X-ray fluorescence (XRF), proton induced X-ray emission (PIXE), atomic absorption spectrometry (AAS) and ion chromatography (IC) were used for the chemical characterization of airborne particulate matter in Santiago, Chile. The PM10 mass and elemental concentration were higher in the winter than in the summer collection period. Analytical quality assessment for NAA, XRF, PIXE, AAS and IC was performed on some samples. Correlations were found between the elements Pb–Br, Si–Ca–Fe, As–Cu–S and also between the fine mass and black carbon concentrations, which could be associated with some relevant sources.

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Abstract  

A purely instrumental neutron activation analysis method, using high resolution gamma-ray spectrometry with intrinsic Ge and Ge(Li) detectors, has been used for the analysis of trace elements in copper concentrate samples. Seven rare earth elements and eight other trace elements were determined with good precision. Standard rocks were also analyzed to check the analytical procedure, and the results obtained are in good agreement with literature values.

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Abstract  

An investigation is made of the importance of (n,,n, ) second-order reaction interferences in reactor neutron activation analysis (NAA), in addition to the commonly considered (n, , ; n, ) interferences. The algorithms for the calculation of the interference are derived from the Bateman-Rubinson equation, taking into account the formation of all m-and g-states involved bum-up effects, and the growth of the interfering radionuclide after irradiation due to a mother-daughter relationship. The following practical cases are examined in detail:138Ba 140La (detemination of La in presence of excess Ba),139La 141Ce (Ce in La),164Dy 166Ho (Ho in Dy),186W 188Re (Re in W) and192Os 194Ir (Ir in Os). A computer search was done for the nuclear data involved in the computation. For139La[(n,; n,; )+(n,; ; n,)]141Ce, and164Dy[(n,; n,; )+ (n,; ; n,)]166Ho experimental checks were performed in the Budapest Research Reactor, which confirmed the calculations showing that the (n,; n,; ) interference gives the largest contribution to the apparent concentration of Ce in La and of Ho in Dy, respectively.

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Abstract  

Mercury pollution in the industrial environment of Chile has been studied using hair as a monitor. Data from samples representing people living in the non-polluted and also from the polluted areas show that, hair is an effective and convenient indicator of environmental mercury pollution in Chile. A major source of mercury pollution and its transport is contaminated water. Hair is found to concentrate mercury from water to an extent of 80 to 500 fold increase in hair concentration. This absorption occurs in a contact time of 24 h and thus provides a means of treating mercury containing water to reduce the mercury to acceptable levels. The capacity of hair for this purpose is about 0.2% which means that, with a kilogram of hair /valued at less than 25 cents/ nearly 20.000 litres of contaminated water /at 0.1 ppm mercury/ can be treated. This is an inexpensive and convenient alternative to conventional ion-exchange processes which are generally very expensive, particularly for developing countries.

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Abstract  

Seven trace elements were determined in milk formulas, powder milk and infant food. Instrumental neutron activation analysis was used for the analysis of Fe, Zn, Co, Cr and Rb, while As and Cu content was determined using radiochemical neutron activation analysis. Differences were found in the trace element content of foods of the same type. Milk formulas are comparable with human milk according to the results obtained for the elements analyzed. The samples of powder cow's milk presented similar concentrations of the elements studied. Liver with vegetables was found to have the highest Cu content. A meal prepared at home, made of beef and fresh vegetables showed a higher trace element content than its similar commercial one. An estimation of the daily intake of the elements analyzed was made and compared with minimum recommended daily ingestion.

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Abstract  

Recommended k0-factors and related nuclear data for use in (n, ) activation analysis are given for 72 isotopes. In addition the basic nuclear constants and experimental parameters needed in the k0 standardization method are reviewed. For convenient data reduction, computer programs were developed.

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Abstract  

During a five-year period, the International Atomic Energy Agency supported a Coordinated Research Programme (CRP) to investigate the quantitative relationship between internal body burdens of a number of elements of environmental health significance and their respective concentrations in hair. The use of nuclear-related analytical techniques, such as neutron activation analysis, X-ray fluorescence, particle-induced X-ray emission and radiotracers, was emphasized. One aspect of the CRP focused on studies in man, using autopsy cases, of mineral distribution in five tissues, i.e. liver, kidney, lung, brain and bone in addition to hair, and the elements of primary importance were As, Cd, Cu, Hg, Pb, Se and Zn. Emphasis was placed on analytical quality assurance. Hair and internal tissue samples were obtained from subjects from Bulgaria, China, the former German Democratic Republic, Hungary, Japan, Norway and Sweden.

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