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  • Author or Editor: J. Mizera x
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Abstract  

As a part of a project aimed at precise correlation of the Jurassic–Cretaceous (J/K) boundary interval in the Tethyan and Boreal realms, neutron and photon activation analyses were employed in geochemical characterization of limestone samples from the Brodno section, Slovakia, which offers a record of hemipelagic marine sediments around the J/K boundary in the Tethyan realm. Nickel and antimony anomalies exceeding almost twenty times the levels in neighboring beds were found near the beds assigned recently to the J/K boundary. Elucidation of their origin (volcanism, isochronous meteoritic impact, concentrating in, e.g., sulfides) requires further investigation.

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Abstract  

Ten selected rock reference materials (USGS diabase W-1, basalt BCR-1, andesite AGV-1, granite G-2, granodiorite GSP-1, and CRPG basalt BE-N, granite GS-N, trachyte ISH-G, serpentine UB-N, glass standard VS-N) were analyzed by instrumental neutron and photon activation analyses. The results have been evaluated on average for the entire set of samples to detect possible systematic deviations of the determined values from the reference values. Out of 47 elements determined, 43 elements have been determined with reasonable agreement (deviation < 10% on average) with the reference values. Au could not be determined because of a high blank from packaging polyethylene foil. Systematically higher Dy and lower Ho and Tm (by about 20% on average) in the present results require further investigation. In several cases, reasons for greater differences between the determined and recommended values could not be traced in the procedures used within the study. The most suspect is the recommended value for W in the CRPG BE-N basalt, which is twenty-five times higher than the present value, probably due to inconsistent contamination from a W carbide mill used in production of this reference material.

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Abstract  

Silver in selected, predominantly biological, reference materials (NIST SRM 1515, 1547, 1549, 1566a, 1571, 1577b, 2704, CTA-OTL-1, and Bowen’s Kale) was determined using neutron activation analysis (NAA) in two different analytical modes: instrumental NAA with epithermal neutrons (ENAA), and NAA with radiochemical separation (RNAA). The ENAA mode was based on long-time 5-hour irradiation of samples in a special Cd lined box with counting after 8-month decay. The RNAA procedure consisted in 20-hour irradiation of samples, their decomposition/dissolution by alkaline-oxidative fusion, and precipitation of AgCl including several purification steps. Both methods provided Ag contents in the analyzed reference materials consistent with certified and/or literature values down to the ng·g−1 level.

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Abstract  

Nutritional status and toxic elements body burden were evaluated in hair of children living in Zanzibar. 18 samples were collected from Zanzibar town and 19 samples from Nungwi village, which is approximately 64 km from Zanzibar town. The analysis was carried out using instrumental neutron activation analysis (INAA). The concentration ranges obtained in this study overlap with the published elemental values of healthy children of the same age group. The concentration levels of K, Zn, Cu, As and Co in hair of children from Zanzibar town were higher than from Nungwi whereas levels of Mn, Br and Sr were lower.

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Abstract  

The determination of gold is based on the photoexcitation reaction 197Au(γ,γ’)197mAu with the half-life of 7.73 seconds and energy of emitted gamma-rays of 279 keV. Three 100 ml aliquots of coarsely ground Au-ore (grains <2 mm) corresponding to ca. 150–180 g were irradiated for 20 seconds with bremsstrahlung of maximum energy 10 MeV produced by a microtron at the electron beam current of 30–40 μA, 1–10 times reactivation was applied. After 3 seconds of decay, samples were measured for 20 seconds using scintillation or semiconductor gamma-spectrometry with the detection limits for an ideal sample down to 0.5 μg·g−1 and 0.1–0.2 μg·g−1 of Au, respectively. Content of U and Th undergoing photo-fission increases the detection limits several times.

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Summary  

A radiotracer method, initially developed to analyze migration from retail plastic food packaging into food simulants, has been developed to assess the measurement of inorganic contaminants migrating from recycled paper and board into real food. This new radiotracer method has been applied to the study of 10 food samples and their corresponding recycled paper and board packaging. Samples of paper and board were irradiated in a thermal neutron flux of 1.26 . 1016n m-2 . s-1 for 15 hours to activate elements of interest. After a decay period of 10 days the paper and board was placed in contact with the corresponding foodstuff. The food was analyzed for any radioactivity migrating from the packaging by gamma-ray spectrometry. Samples were analyzed regularly during the 90 days contact time. Detection limits for the determination of migration was as low as a few µg/kg in the food. Results from the migration study have shown that, of the 60 elements measured, only Zn and Fe were detected in food, at concentrations of 0.012-0.25, and 0.045-0.11 mg/kg, respectively. This was despite the recycled paper and board samples being highly elevated in many other elements such as Cr (0.9-15.1 mg/kg) and Ba (3.3-75.4 mg/kg). The level of migration of Zn and Fe into food from packaging was insignificant compared to the UK recommended daily allowances of 15 mg, and, therefore, represented no hazard to human health.

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Summary  

Fruitbodies of wild-growing macromycetes (mushrooms) of various genera and species collected in localities with different geochemical features and man-made burden in the Czech Republic were analyzed using the short-term instrumental neutron activation, with both thermal and epithermal neutrons. Analytical possibilities of these methods were compared. Na, Mg, Al, Cl, K, Ca, V, Mn, Cu, and Br were determined regularly, whereas S, Ti, Rb, Cs, Ba, and Dy were determined occasionally with thermal neutron activation at irradiation-decay-counting times mode of 1-10-10 minutes. Because of high concentration of K and P in the macromycete dry matter (2-7% and 0.5-1%, respectively) and also high Cl concentration in some genera (up to 2.5%), all “1/v” absorbers, epithermal neutron activation in Cd box (1 mm thick wall) substantially suppresses their macroactivities and enhances sensitivity in the determination of elements with significant resonance integrals. Cu, Se, Rb, Ag, Hf, and sometimes Ba are determinable in the mode of 60-30-60 seconds, while K, Cu, As, Br, Rb, In, I, U (in some species also Co, Zn, Cs, Ba, and Hg) in the mode of 1-13-13 minutes. However, Na, Mg, Al, Cl, and Mn determination is not possible this way, as the (n,p) and (n,α) interfering reactions with fast neutrons and high K, P, and other interfering elements content make great interference contributions. Information about content of the essential and toxic elements in mushrooms is important in nutritional studies, because mushrooms form a non-negligible part of diet in many countries.

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Abstract  

As a part of geophysical, stratigraphical and paleontological study aimed at precise correlation of the Jurassic–Cretaceous (J/K) boundary interval in the Tethyan and Boreal Realms, detailed magnetostratigraphic and biostratigraphic profiles with well-calibrated J/K boundary have been selected from several localities for geochemical characterization. Instrumental and radiochemical neutron activation analyses (INAA and RNAA, respectively) were employed in the characterization of a vertical profile around the supposed J/K boundary in the Boreal Realm situated on the Nordvik Peninsula, Northern coast of Middle Siberia (Laptev Sea), Russia, for which an iridium anomaly has been reported in literature. INAA enabled determination of about forty major and trace elements. An RNAA procedure for assaying platinum group elements (PGE) has been tested consisting in sample decomposition by alkaline–oxidative fusion, reduction of PGE, and precipitation of their sulphides. Despite several difficulties, the procedure enabled to found Pt and Ir at ppb and sub-ppb levels, respectively, in several samples, namely in pyrite aggregates originated probably in diagenetic reductive processes following decomposition of burried organic matter. However, the existence of a pronounced PGE spike reported previously for the J/K boundary on the Nordvik Peninsula has not been confirmed.

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Abstract  

A large set of impact glasses from the Zhamanshin crater in Kazakhstan was analyzed by various modes of instrumental neutron activation analysis, supplemented by instrumental photon activation analysis and prompt gamma-ray activation analysis. Results of the determination of more than forty major and trace elements have shown that the analyzed set of homogeneous, tektite-like impact glasses with size of several centimeters and of various forms could be divided into two geochemically different groups. The lustrous, silica rich (acidic) glasses with high Ni content have been classified conventionally as irghizites. The dull, silica poor (basic) glasses with very low Ni content should not be confused with the large, heterogeneous impactite forms—zhamanshinites, but considered as a separate type of impact glass. Within both primary groups, further division has been suggested based on lower contents of Ni in an irghizite subgroup, and evidence of mixing of source materials for both primary groups in a part of the basic glasses. Based on the contents of Ni, Cr, Mn, Fe and Co, an ordinary chondrite impactor has been suggested with its contribution to the irghizite matter ranging between 4 and 21%. Possible source materials and impact processes leading to irghizite formation have been outlined.

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Abstract  

The potential of photon activation analysis (PAA) for multielement trace analysis can hardly compare with that of neutron activation analysis (NAA). However, PAA appears superior over NAA for the determination of a number of elements, namely C, N, O, F, Mg, Si, Ca, Ti, Ni, Sr, Y, Zr, Nb, Sn, Tl and Pb in geological, environmental and biological materials. Most of these and other elements can be determined using nondestructive, instrumental PAA (IPAA), especially in geological materials. The possibilities of IPAA for multielement analysis using photoexitation and other photonuclear reactions are reviewed and compared with those of instrumental NAA (INAA), namely for geological materials. The need for and usefulness of radiochemical PAA (RPAA) procedures are also discussed.

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