In order to reveal the quality and isotopic characteristics of lagoon waters in Niigata Prefecture in recent years, the nutrients concentrations of nitrogen (N) and phosphorus (P) as well as oxygen stable isotope ratios(i.e., δ18O) in water samples of Sakata and Toyanogata were measured. Samples were regularly taken at the fixed sampling points from these lagoons, and depth distribution was surveyed at one point in Toyanogata. In addition, δ18O and nutrients concentrations of water samples in Zhalong Wetland at Heilongjiang Province in China were also determined. Consequently, the following matters have been mainly clarified. (1) δ18O values of sample waters in Zhalong Wetland are generally large probably because of the effect of evaporation, whereas those of Sakata lagoon are large which may be due to the biological process such as the activity of plankton. (2) Considering the results of nutrients concentrations, the water quality of lagoon (Sakata and Toyanogata) waters in Niigata Prefecture is better than that of Zhalong Wetland in China.
The direct method using a toluene scintillator has already been proposed for the determination of radon(222Rn) concentration in environmental water samples measuring with a liquid scintillation counter, because the parameters(the gas-liquid distribution coefficient, etc.) of toluene are well known. However toluene has a high volatility and deleterious health effects. This paper presents a measurement method for radon concentration in water using a conventional liquid scintillation counter and a simplified liquid scintillation counter with less hazardous scintillation cocktails. The measurement data have led to more accurate results using an integral counting method.
Fukushima and adjacent regions still have a large number of high dose rate areas called hotspots. It is necessary to know these hotspots for efficient decontamination of radioactive substances such as 137Cs and for relief of residents coming home. To find the hotspots rapidly, we have to specify the direction of the area where the dose rate is at least 1μSv/h higher than those of surroundings. We have developed a detector that consists of an acrylic filter and three NaI(Tl) scintillation survey meters, and the detector can be expected to indicate the direction of the hotspot in the short time. A basic performance of the detector was examined by using acrylic filters of 10, 15, 20 and 25cm diameter and a tiny sealed 137Cs source of 3MBq as the alternative of a hotspot. It demonstrated the possibility of identifying the direction of γ-rays emitted from the source in 90 seconds.
Root uptake of 137Cs from sedimentation sludge-amended soils by Komatsuna (Brassica rapa var. perviridis) was studied. The sludge was mixed to an initial soil mixture of Akadamatsuchi, Kurotsuchi and muck to produce three kinds of soils:0S soil(sludge:initial soil mixture=0L:5L), 0.5S soil(0.5L:4.5L), and 1.5S soil(1.5L:3.5L). Komatsuna was grown for 33 days on those soil mixtures. Plant height above ground was similar during cultivation period among three kinds of soils. Fresh weights of Komatsuna at harvest increased in order of the0S, the 1.5S, and the 0.5S soil sample. These results mean no growth suppression effect of the sludge on Komatsuna under our experimental conditions. Activities of 137Cs in Komatsuna at harvest were 1.89Bq/kg-dry for the 0S sample, 153Bq/kg-dry for the 0.5S sample, and 400Bq/kg-dry for the 1.5S sample. The activities of radiocaesium(134Cs+137Cs) per unit wet weight for all the samples were below 100Bq/kg, which is the new standard limit for general foods by Japanese guidelines. The soil-plant transfer factor of 137Cs was 0.1 for both the 0.5S and the 1.5S soil samples when the transfer parameters were given for dry weight. Similarly, the transfer factor was 0.007 on a wet weight basis. The transfer factor value for the sludge was within the range of the values reported in the previous report for leafy vegetable, which were investigated before the Fukushima Daiihci Nuclear Power Plant accident.
We examined the effect on shifts of 137Cs from old organs to newly other organ with grafting scion contaminated by radionuclides onto non-radioactive contamination tree in grapes. 137Cs of about 20% in the scion had transferred to newly organs. In the scion, the concentration of 137Cs in bark after harvest was similar to that measured before grafting, but the concentration of 137Cs in wood after harvest was lower than that measured before grafting. We concluded that transferability of 137Cs from old branches to fruits had contributed much more than that from soil known in previous research.
After the Fukushima Daiichi Nuclear Power Plant accident, soil collected in Fukushima Prefecture was separated into magnetic and non-magnetic parts with a magnet. Radioactivity of 134Cs and 137Cs was measured for each part. It was found that the radioactivity per weight of the magnetic part is 4 times as high as that of the non-magnetic part.
There is need for a single quantity used in radiological protection both for internal and external exposures. This paper describes the concept of protection quantities for internal radiation exposure, in which the following problems specific to the assessment of internal doses were taken into account：(1)protracted exposure by radionuclides in the organs, (2)element-dependent behaviors in the body, (3)unevenness of doses among organs, (4)localization of cells at risk within a specific organ, (5)contribution of non-penetrating radiations(e.g. α-particles) and (6)very high doses to a very small volume by ‘hot particles’. In addition, the processes how the dose coefficients and the bioassay data were determined by the International Commission on Radiological Protection(ICRP) are made clear by putting emphasis on explanation of the ICRP biokinetic models such as Human Respiratory Tract Model, Human Alimentary Tract Model and element specific systemic models. It is expected that this paper could contribute to better understanding of the ICRP system of dose assessment for internal exposure and appropriate application of the dose coefficients and the bioassay data for individual internal monitoring to radiological protection.
When a transition metal ion with an electron configuration of dn(n=4-7) is octahedrally coordinated by ligands, the ground state has a possibility to change the spin state between high-spin(HS) and low-spin(LS) states by external stimuli. Such the HS-LS transition is called spin‐crossover transition. The spin-crossover phenomenon has attracted much attention since the discovery of photo-induced spin transition called LIESST(Light Induced Excited Spin State Trapping) for [Fe(ptz)6](BF4)2(ptz=1-propyltetrazole). Being stimulated by the discovery of LIEEST, various kinds of spin-crossover complexes showing LIESST have been reported for Fe(II) and Fe(III) complexes. In the case of mixed-valence complexes whose spin states are situated in the spin-crossover region, it is expected that an extended spin crossover phenomenon coupled with spin and charge takes place between neighboring metal ions in order to minimize the free energy in the whole system. Recently, we have discovered a spin-entropy driven charge transfer phase transition around 120K, where the electrons of Avogadro's constant transfer cooperatively between the FeII and FeIII sites, for a mixed-valence ferromagnetic complex, (n-C3H7)4N[FeIIFeIII(dto)3](dto＝C2O2S2), exhibiting ferromagnetism. The charge transfer phase transition and the ferromagnetic transition remarkably depend on the cation size. In order to control the magnetic properties and the electronic state in the dto-bridged iron mixed-valence system by means of photo-irradiation, we have synthesized a photo-sensitive organic-inorganic hybrid system, (SP)[FeIIFeIII(dto)3](SP=spiropyran), and found the photo-isomerization of SP from the closed form to the open one in (SP)[FeIIFeIII(dto)3], which induces the charge transfer phase transition in the two-dimensional honeycomb network structure of [FeIIFeIII(dto)3]∞, and enhances the ferromagnetic transition temperature. Moreover, we have synthesized a mto (=C2O3S) bridged iron mixed-valence complex, (n-C4H9)4N[FeIIFeIII(mto)3] consisting of FeIIIO3S3 and FeIIO6 octahedra, and found a rapid spin equilibrium between the HS(S=5/2) and LS(S=1/2states) at the FeIIIO3S3 site in a wide temperature range, which induces the iron valence fluctuation through the ferromagnetic coupling between the LS(S=1/2) of the FeIIIS3O3 site and the HS(S=2) of the FeIIO6 site.
A large vibration of an atom in an oversized atomic cage, so called rattling, has effects of reducing thermal conductivity and improving thermoelectric properties. Since the mechanism of thermal scattering by rattling is unclear, rattling has been studied intensively with motivation for developing new thermoelectric materials having higher thermoelectric properties. This paper provides an introduction how neutron scattering is used for studying the mechanism.