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Abstract  

Rice grain samples and surface paddy soil samples were collected from 20 sites throughout Aomori Prefecture, Japan, and the concentrations of 25 elements in the polished rice and 33 elements in the soils were determined by neutron activation analysis, inductively coupled plasma-mass spectrometer or atomic adsorption spectrometer. The range of essential element concentrations in the polished rice was within one order of magnitude, however, the range for most of the trace elements was more than one order of magnitude. The range of element concentrations, except for I, in the paddy soils was within one order of magnitude. The ±95% confidence intervals of the soil-to-polished rice transfer factors for all elements, except for Pb, were within two orders of magnitude, and the geometric mean values were as follows: Cl, Mo and Zn (0.1–1); K, Cu, Cd, Rb, Mg, Mn, and Ag (0.01–0.1); Ni, As, Ca, Se and I (0.001–0.01); Na, Cs, Sr, Co, Cr, V, Ba, Pb, Fe and Al (<0.001).

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Abstract  

The behavior of uranium under various redox conditions was investigated in the brackish Obuchi lake surrounded by an uranium enrichment plant and facilities currently under construction for reprocessing of spent nuclear fuel in Rokkasho Village in northern Japan. Our investigation showed that uranium in water under oxic conditions can be explained by the simple mixing of freshwater and seawater, and the source of uranium in the lake is mainly seawater. The ratios of 238U/salinity under oxic conditions were approximately 0.09-0.12 g.l-1.psu-1. However, the ratios of 238U/salinity in bottom layer water under anoxic condition in summer were lower (0.07-0.09 g.l-1.psu-1) than those in seawater. 238U concentrations in pore water sampled under anoxic conditions were very low (0.05-0.06 g.l-1.psu-1). Moreover, the relationships between the 238U/Al ratios and the Fe/Al ratios of particle substances were strongly correlated. This suggests that uranium in the bottom-layer water may be precipitated to an insoluble form in the anoxic state, and Fe is the major carrier of insoluble uranium.

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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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Summary  

Major and trace elements in soil and plant samples, including standard reference materials were determined by means of neutron activation analysis (NAA) and inductively coupled plasma-mass spectrometry (ICP-MS). The analytical procedure for NAA utilized dried powder samples. The concentration of iodine in soil samples was determined by radiochemical NAA. The irradiated samples were cooled and then counted with a Ge gamma-ray detector connected to a multi-channel analyzer. For ICP-MS analysis, the samples were decomposed by microwave digestion with an acid mixture. The concentration of I in the soil samples was measured by ICP-MS after separation by ignition. The analytical values for most elements in the environmental samples by both methods were in good agreement, whereas sample treatments were different. Measured value of Zr in the soil samples by ICP-MS was about 50% lower than that by NAA. It should be assumed that some minerals of Zr in soil particles were not entirely dissolved by the acid mixture. Analytical results of Cd for three different Cd levels in unpolished rice flour samples (NIES 10-a, b and c) determined by ICP-MS were in agreement with certified values. The concentration of Cd in the sample with the lowest Cd level, as determined by NAA with 57% counting error, was 3 times higher than the certified value.

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Journal of Thermal Analysis and Calorimetry
Authors:
C. Shimasaki
,
T. Kanaki
,
S. Takeuchi
,
K. Hasegawa
,
D. Horita
,
E. Tsukurimichi
, and
T. Yoshimura

Abstract  

The pyrolysis of trimethylsilyl derivatives of saccharides (1) was investigated by DTA-TG, MS, GC/MS and TG-GC/MS. The DTA-TG/DTG curves showed that the pyrolysis of 1 occurred in one stage. The exothermic peaks were due to sublimation or thermal decomposition by vaporization. The cleavage mechanism by electron impact of 1 was classified into four categories: 1) stepwise elimination of the side-chain, 2) cleavage of the side-chain, 3) cleavage of the pyranose ring, and 4) cleavage of the pyranose ring and side-chain at the same time. The mass-spectrum for 1 revealed the main common four fragment ions, such asm/z 73, 191, 204 and 217, with cleavage of the pyranose ring. These fragment ions were detected with a similar retention time in the gas cromatogram by GC/MS or TG-GC/MS. The retention time for 1 increased in the sequence aldopentose<ketohexose<aldohexose. This result indicates that the trimethylsilyl derivatives are thermally stable. Subsequently, the pyrolysis regime for 1 obeyed apparent 1/2-order kinetics and their apparent activation energy was estimated as 75–100 kJ/mole.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
Naofumi Akata
,
H. Kawabata
,
H. Hasegawa
,
T. Sato
,
Y. Chikuchi
,
K. Kondo
,
S. Hisamatsu
, and
J. Inaba

Abstract  

The atmospheric concentrations and deposition fluxes of 7Be and 210Pb were observed biweekly in Rokkasho, Japan on the Pacific Ocean coast at the northern end of Honshu Island, from March 2000 to March 2006, to clarify their regional features. Seasonal variation pattern of atmospheric 7Be concentrations had double peaks, and that of 210Pb had a single peak. Deposition fluxes of 7Be and 210Pb showed the same patterns. The total deposition pattern of 7Be was similar to that commonly seen on the Pacific Ocean side of northern Honshu Island, while the pattern of 210Pb was similar to that commonly seen on the Japan Sea side. The lack of high spine mountains windward in Rokkasho may be the cause of this ambiguity in the winter monsoon season. Total deposition velocities and scavenging ratios of 210Pb were similar to those of 7Be from spring to fall, and showed that both nuclides had a similar removal process from the atmosphere. However, the scavenging ratios of 210Pb were slightly larger than those of 7Be in winter, indicating different behaviors for both nuclides in the scavenging process. The scavenging ratios of both nuclides inversely correlated with precipitation rate, and the ratios in winter were larger than in the other seasons.

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Abstract  

Atmospheric concentrations of 210Pb change with various factors such as meso-scale meteorological conditions. We have already reported the biweekly atmospheric 210Pb concentrations in Rokkasho, Japan for 5 years and found that they had clear seasonal variations: low concentrations in summer and high values in winter to spring. To study the reasons for the seasonal variations, the origins of the air mass flowing to Rokkasho were analyzed by 3-D backward air mass trajectory analysis. Routes of the calculated trajectories were classified into four regions: northeastern and southeastern Asian Continent, sea and other regions. The atmospheric 210Pb concentrations were well correlated with the frequency of the routes through the northeastern Asian Continent. A non-linear multiple regression analysis of the 210Pb concentrations and the relative frequencies of the four routes showed good fitting of the predicted values to the observed ones, and indicated that the atmospheric 210Pb concentrations in Rokkasho depended on the frequency of the air mass from the northeastern Asian Continent.

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Abstract  

We investigated the distribution of aquatic plants and the absorption of radionuclides by them in the brackish Lake Obuchi, Japan, which is bordered by nuclear fuel cycle facilities. We studied 5 species of submerged plants: Zannichellia palustris, Ruppia maritima, Potamogeton pectinatus, Zostera japonica, and Z. marina. The plants contained many elements, including radionuclides. The concentrations of 238U, 137Cs, and 90Sr in Z. marina were 11.3-12.4, 0.000-0.144, and 0.151-0.202 Bq.kg-1 dw, respectively. Those in Z. japonica were 5.2-8.8, 0.000-0.267, and 0.081-0.175 Bq.kg-1 dw, respectively. The concentrations of these radionuclides in the plants tended to be higher in higher-salinity regions than in lower-salinity regions of the lake. We found a close relationship between photosynthetic activity and the absorption of stable Sr by plants in the laboratory. Salinity, illumination, and water temperature influenced the photosynthetic activity of the plants and the consequent absorption of elements.

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Abstract  

Lake Obuchi is on the Shimokita Peninsula, Aomori Prefecture, Japan, near several nuclear fuel-related facilities. The lake contains from oligohaline to polyhaline regions, and the salinity fluctuates greatly both spatially and temporally. This study examined the possible effect of salinity on biological concentrations of 137Cs in phytoplankton on the basis of a culture experiment using stable Cs and phytoplankton species isolated from the lake. In both Cyclotellaand Skeletonema, the biological concentrations of Cs varied with salinity conditions, and a positive linear relation was found between maximum proliferation and biological concentrations of Cs.

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