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  • Author or Editor: H. Maeda x
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Abstract  

Concentrations of239+249Pu in environmental samples were detemined by ICP-MS and spectrometry, showing consistent results, which suggests an applicability of ICP-MS to239Pu and240Pu measurement. The activity ratios of238Pu/239+240Pu and240Pu/239Pu were significantly different in samples from the general environment and near Sellafield reprocessing plants, indicating the usefulness of these ratios for identification of the Pu contamination source.

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Abstract  

Tritium concentrations were analyzed in organic and water fractions of fresh pine needles, dead and degraded pine needles accumulating on a pine forest floor to examine tritium cycle in a forest ecosystem. Tritium concentration was higher in the organic fraction of dead and degraded pine needles compared to others, suggesting two tritium sources. Rain is responsible for water fractions in the samples, while atmospheric hydrogen and methane are speculated to be responsible for high tritium level in the organic fraction of dead and degraded pine needles.

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Abstract  

Tritium concentrations in rain collected at Fukuoka, Japan from 1982 have been measured. From May 1996 tritium concentrations and chemical species have been analyzed for each rain to examine their relationship. Recent rain was concluded not to be affected by tritium from atmospheric nuclear tests. Tritium concentrations showed a seasonal pattern, high during winter and spring and low during summer and fall and had positive correlations with non-sea-salt SO4 −2, indicating a long distance transport of acidic materials as tritium from continental China.

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Abstract  

Surface seawater and water vapor about 10 m above the sea level were collected in the Pacific and Indian Oceans during the expedition of KH-96-5 to examine tritium concentrations in open sea. The tritium concentration in the water vapor was one order of magnitude higher than that in the surface seawater, attributed to downward movement of naturally occurring tritium from stratosphere to troposphere.

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Abstract  

Variation of tritium concentration was examined for 100 days in the course of degradation of fresh pine needles, which were left on a pine forest floor. No difference was observed on free water tritium (FWT) and organically bound tritium (OBT) concentrations of sterilized samples by gamma-ray irradiation or fumigation and control samples, attributable to incomplete sterilization. The OBT concentrations did not increase within the experimental period as the level of humus collected from the forest floor. The results suggest that a longer degradation time, more than 100 days, is necessary to elevate OBT up to the level, which is observed in the general environment.

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Abstract  

pH dependence of the adsorption of Na, Sc, Ga, As, Se, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, and Pd on -Fe2O3 from a 0.1 mol dm–3 NaCl solution was studied by using a multitracer technique. Desorption of the metal ions from the -Fe2O3 with the adsorbed metal ions at pH 11 was also studied by lowering the pH of the suspensions. The desorption curve of each element was in good agreement with the adsorption curve except for Ru and Rh under conditions studied. Adsorption kinetics showed that the adsorption of most metal ions increases with shaking time before an adsorption equilibrium is attained. An increase in the adsorption was also observed with an elevation in temperature for the elements, suggesting that the adsorption is involved in chemisorption.

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Abstract  

A cyclic activation analysis method with a 100 μg252Cf source was developed for the determination of low concentrations of fluorine in glasses containing high concentrations of oxygen. Factors influencing errors in the analysis were investigated quantitatively. The activation cross-section of19F(n, α)16N for252Cf fission neutrons was determined. A brief description is given of the cyclic activation, analysis apparatus, and also the modified optimization of the cyclic operation. The usefulness of the analysis is demonstrated by application to a fluorine volatilization study.

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Abstract  

Aerosols and source related materials (fly ash from refuse incinerators, vehicle exhaust and soil) were collected in April, 2002 in the northern areas of Jeju-do, Korea, and the Pb isotopic ratios (207Pb/206Pb and 208Pb/206Pb) of the samples were measured in order to estimate the Pb sources of the aerosols. The Pb isotopic ratios of the aerosols were classified into two groups, depending on the sampling date. One group showed similar Pb isotopic ratios with those of the source related materials, suggesting that the contribution of the regional sources to the aerosols was very large. The other showed different Pb isotopic ratios from those of the regional sources and relatively high Pb isotopic ratios compared to the ratios of the first group. The results suggest that in the continental Asia there seems to be a long range transport of Pb with high ratios in desert sands, which are carried by northwest seasonal winds.

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Abstract  

129I-Mössbauer spectroscopic data are presented for the titled iodides. Comparison of Mössbauer parameters of the mixed-valence biferrocenium iodides suggests that the rate of intramolecular electron transfer depends on the nature of biferrocenium cation moiety in solid state.

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Abstract  

The multitracer technique was applied to elucidate of influence of humate formation on adsorption behavior of ultratrace elements. Dissolved fractions of Co, As, Rb, Sr, Y, Zr, Ba, Ce, Eu, Gd, Tb, Yb, Lu, Hf, Re and Pt in contact with kaolinite or silica gel were determined simultaneously either in the presence or absence of humic acid, which was partly adsorbed on the solid. Percentage of dissolved fraction of rare earth elements was identical to that of humic acid, indicating high stability of the rare earth-humate complex. Hydrolysis was the most important factor controlling the behavior of Zr and Hf. Both hydrolysis and humate complexation influenced the adsorption of Co, Sr, Ba and Pt, whereas neither affected the distribution of As, Rb and Re.

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