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Abstract  

We have clarified vertical distribution of thirty and more elements in the Yatsu tideland sediment by instrumental neutron activation analysis (INAA) and prompt g-ray analysis (PGA). The distributions of elements were categorized into three groups according the tendency of each vertical distribution. Chemical states of iron in the sediments were investigated by Mössbauer spectroscopy. In the distribution of iron species, maximum pyrite distribution was found in the middle layer. Paramagnetic high-spin Fe2+ distributed complementarily to pyrite, suggesting that the Fe2+ was used for pyrite formation.

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Heat capacities of the thiourea clathrate compound of 1,1,2,2-tetrachloroethane, {(NH2)2CS}3(CHCl2)2, were measured at temperatures between 13 and 330 K. Two phase transitions were found. The enthalpy and entropy changes of the transition are 5940 J·mol−1 and 28.1 JK−1· mol−1 for the one occurring at 224 K and 2756 J·mol−1 and 11.3 JK−1·mol−1 for the other at 248 K. It is concluded from the transition entropy values that the guest molecules are orientionally disordered nearly to the same extent as in the neat liquid.

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Abstract  

In order to investigate the transition of tidelands, we collected sediments in Yatsu tideland and Nekozane river mouth in Tokyo Bay. The vertical distributions of elements were determined by instrumental neutron activation analysis and prompt gamma-ray analysis. In Yatsu tideland the vertical distribution changed in a great extent, which was considered as an influence of the neighboring reclamation. They were categorized into four groups, and two parameters were created by applying principal component analysis. Chemical states of iron and sulfur were also investigated by Mössbauer spectroscopy and X-ray absorption fine structure. These results show that Yatsu tideland became an anaerobic environment.

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Abstract  

In order to estimate the source in pelagic sediments, principal component analysis (PCA) was applied to the data matrix which was made by chemical compositions of sediments measured by instrumental neutron activation analysis (INAA) and prompt gamma-ray analysis (PGA). The results of PCA represented 3-factor models in each sediment, explaining 58–98% of the total variations in the sediments. A comparison of eigenvectors of terrigenous elements indicated the existence of 2 sources. Group 1 is suggested to be continental dust, whereas Group 2 is suggested to be volcanic rock. Variation of K/Ti ratio and Eu anomaly of sediments supported the above results.

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Abstract  

Mössbauer spectroscopy was applied to natural chromite samples from ophiolite complexes in the Philippines. Chemical and structural characterization of the chromite samples was also carried out using X-ray absorption fine structure (XAFS), X-ray diffraction (XRD) and X-ray fluorescence spectrometry (XRF). The Mössbauer spectra of the samples consisted of quadrupole doublets ascribable to Fe3+ in octahedral site, Fe3+ in tetrahedral site, and Fe2+ in tetrahedral site. The relative percentage of Fe3+ and Fe2+ ions suggested that these Philippine samples were formed under relatively high oxygen fugacity.

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Abstract  

Airborne particulate matter was collected at the intersection of Industrial Road in Kawasaki-city, Kanagawa, Japan using a 12-stage low-pressure impactor. High concentrations of airborne particulate matter have been observed in this area. The collected samples were analyzed for 34 elements by instrumental neutron activation analysis (INAA), and data on the elemental concentrations were obtained. High concentrations of fine particles of As, Br, Sb, V, and Zn were observed. It was further observed that these fine particles were originated predominantly from the wear of tires and brakes, and not from automobile exhaust emissions.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
M. Oshima
,
Y. Toh
,
A. Kimura
,
M. Ebihara
,
Y. Oura
,
Y. Itoh
,
H. Sawahata
, and
M. Matsuo

Abstract  

By combining neutron activation analysis with multiple gamma-ray detection (gamma-gamma coincidence), we have proved better sensitivity and resolution for the trace element analysis than the ordinary single gamma-ray detection method. We now try to apply the multiple gamma-ray detection method to the prompt gamma ray analysis (PGA). We have established a new cold neutron beam line for PGA in Japan Research Reactor, JRR-3M, at Tokai establishment of Japan Atomic Energy Research Institute (JAERI). It consists of a beam shutter, a beam attenuator, a gamma-ray detector array, a sample changer, and a beam stopper. We construct a high-efficiency gamma-ray detector array specially designed for this purpose. Its performance has been evaluated with the Monte Carlo simulation code, GEANT 4.5.0.

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Abstract  

Neutron induced prompt gamma-ray analysis (PGA) and instrumental neutron activation analysis (INAA) have been applied to the sediments collected from the Yasaka River estuary in Oita Prefecture, Japan. The vertical distribution of 33 elements in the sediments has been determined and compared with that in more polluted estuarine sediments. While the S content increased with increasing depth because of a sulphide accumulation under reducing condition, the increase in sulphide-forming elements such as Ag, Cd, Co and Zn was not observed in the deeper section of the Yasaka River estuarine sediments.

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Summary  

A method has been developed for analyzing pyrite quantitatively in the sediments of Erhai Lake in southwest China using 57Fe Mössbauer spectroscopy combined with a series of acidic pre-treatments. Following a washing with an alkaline solution (0.1N NaOH), the sediment samples were successively treated using HCl, HF, and then HCl (65 °C). The residues thus prepared were analyzed for pyrite using 57Fe Mössbauer spectrometry. The presence of pyrite was also confirmed in the acidic residues of the sediments using sulfur K-edge X-ray absorption near edge structure. This method can be used to measure pyrite in aquatic sediments, especially when the concentration of pyrite is very low and the particles of pyrite are small or the crystallinity is low, and even in amorphous status. In addition, vertical variations of pyrite contents are positively correlated with organic matter and negatively correlated with hematite, superfine paramagnetic ferric iron and sedimentation rate in the cored sediment from the Erhai Lake. All these geochemical indicators may also reflect environmental changes in sedimentation conditions and diagenesis.

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