The concentrations of 137Cs and other essential and trace elements were determined in soils and in cabbage heads collected from 8 agricultural fields in Aomori Prefecture, Japan and the soil-to-plant transfer factors were determined. The 95% confidence intervals of the elements, excluding 137Cs, La and Ce, were within 2 orders of magnitude. The transfer factor of 137Cs was approximately 4 times higher than that of Cs, and they were well correlated. In addition, the distributions of elemental concentrations in different leaf positions of a cabbage plant were also determined and were divided into three groups according to their different distribution patterns in the leaf positions. These patterns were as follows: (1) the concentrations of the elements in older (outer) leaves were higher than in younger (inner) ones (Ca, Sr, etc.), (2) the concentrations of the element had a relatively constant value independent of their leaf position (K, Rb, etc.), and (3) the concentrations of the elements were higher in both the older and younger leaves compared to the leaves in the middle portion (Zn). The percentage distribution of the dry weight contents in the edible leaves of cabbage plants was 41% at harvest time, however each element had different distribution patterns.
The values of Sb(III), Tl(I), Te(IV), and biological substance, DNA determined by sub- and super-equivalence method of isotope dilution analysis (SSE-IDA) and substoichiometric isotope dilution analysis (Subst-IDA) under the same condition were compared. From the results, it was proved that SEE-IDA did not need the strict condition necessary for Subst-IDA and the determination by SEE-IDA was possible within the error of a few percent, and the range of determination was wider than that of Subst-IDA. The various variants of SSE-IDA reported so far were classified into SEE-Reverse-IDA and SEE-Direct-IDA. Finally, the characteristics of SEE-IDA allowing accurate determination were discussed and summarized.
A new sub-superequivalence method of radiometric analysis is proposed, which is derived by combining the sub-superequivalence method of isotope dilution analysis with substoichiometric radiometric analysis. This method using redox reaction is applied for the determination of trace amount of antimony and was proved to be an excellent technique. The fundamental problems of this method are discussed analytically.
Authors:H. Tsukada, A. Takeda, H. Hasegawa, S. Ueda, and T. Iyogi
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.
Authors:H. Tsukada, H. Hasegawa, A. Takeda, and S. Hisamatsu
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).
Authors:K. Shinotsuka, H. Yoshioka, T. Omori, and K. Hasegawa
The reduction reaction mechanism of carrier-free125Sb in HCl solution was studied kinetically. Sb(III) and Sb(v) were separated by solvent extraction using n-benzoyl-n-phenylhydroxylamine(BPHA) in chloroform at different constant time in interval and the reaction rate was determined by measuring the radioactivities of125Sb in both organic and aqueous phases. Plot of log[125Sb(V)/ [125Sb(III)+125Sb(V)] against the elasped time do not give straight lines. The curves can be solved to be ABC type reactions by a non-linear squares. On the basis of dependence of the reactions, overall reactions can be expressed as follows;
Authors:K. Norisuye, K. Okamura, Y. Sohrin, H. Hasegawa, and T. Nakanishi
The present paper describes a new analytical method for determining the 240Pu/239Pu isotopic ratio and 238Pu/239+240Pu α -activity ratio in seawater, both of which are important parameters for determining Pu sources in the ocean. Plutonium
isotopes were preconcentrated from a large volume of seawater (4700-10800 liter) by solid phase extraction using MnO2-impregnated fibers and eluted into 3M HCl. After the elution, the Pu species of all oxidation states were converted to Pu(IV)
using NaNO2, purified by solvent extraction using thenoyltrifluoroacetone (TTA)-benzene, and concentrated in 5 ml of 0.2M HNO2. The 240Pu/239Pu and 238Pu/239+240Pu ratios in the 5-ml final solution were determined by inductively coupled plasma-mass spectrometry (ICP-MS) and α-spectrometry,
respectively. A pg level of Pu, which was a sufficiently large amount for the determination, was obtained by the solid phase
extraction. Through the redox conversion and solvent extraction, the Pu species, such as Pu(III), Pu(IV) and Pu(VI), were
collected at a high recovery of 96±2% (n=3) despite the presence of large amounts of Mn, and interfering 238U (3.3 µg. l-1in seawater) was effectively removed with a decontamination factor of 1.7·107. The accuracy of the method for the 240Pu/239Pu ratio was verified using reference materials of seawater and a terrestrial soil sample. The present technique was applied
to the determination of the 240Pu/239Pu and 238Pu/239+240Pu ratios in coastal and oceanic water.
Authors:S. Ueda, H. Hasegawa, Y. Takaku, and K. Kondo
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.
Authors:H. Hasegawa, N. Akata, H. Kawabata, Y. Chikuchi, T. Sato, K. Kondo, and J. Inaba
7Be deposition fluxes and atmospheric concentrations were measured at Rokkasho Village, Aomori Prefecture, Japan, from 2000
to 2005. It was confirmed that the 7Be deposition fluxes were minimum in summer, and the fallout maximizes in winter. The atmospheric concentration of 7Be was especially low in summer, and high in the other three seasons. A positive correlation was observed between the amount
of precipitation and 7Be deposition. Clear seasonal differences were evident among the ratios of 7Be deposition flux to precipitation amounts in the four seasons. The ratios were especially high in winter, higher than those
in the other three seasons. 7Be deposition flux was estimated by a simple simulation model using atmospheric 7Be concentrations and local meteorological data. As a result, the estimated deposition value was relatively lower than the
measured value in winter.
Authors:Naofumi Akata, H. Kawabata, H. Hasegawa, T. Sato, Y. Chikuchi, K. Kondo, S. Hisamatsu, and J. Inaba
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.