Tamao Hatta

Speciation of Radioactive Soil Particles in the Fukushima Contaminated Area by IP Autoradiography and Microanalyses

Radioactive soil particles several tens of micrometers in size were collected from litter soil in the radiation contaminated area by the Fukushima nuclear plant accident and characterized using electron and X-ray microanalyses. The radioactive particles were discriminated by autoradiography using imaging plates (IP) on which microgrids were formed by laser ablation in order to find the particles under microscopy. Fifty radioactive particles were identified and classified into three types from their morphology and chemical composition, namely: (1) aggregates of clay minerals, (2) organic matter containing clay mineral particulates, and (3) weathered biotite originating from local granite. With respect to the second type, dissolution of the organic matter did not reduce the radiation, suggesting that the radionuclides were also fixed by the clay minerals. The weathered biotite grains have a plate-like shape with well-developed cleavages inside the grains, and kaolin group minerals and goethite filling the cleavage spaces. The reduction of the radiation intensity was measured before and after the trimming of the plate edges using a focused ion beam (FIB), to examine whether radioactive cesium primarily sorbed at frayed edges. The radiation was attenuated in proportion to the volume decrease by the edge trimming, implying that radioactive cesium was sorbed uniformly in the porous weathered biotite.

Light-induced degradation dynamics in realgar: in situ structural investigation using single-crystal X-ray diffraction study and X-ray photoelectron spectroscopy

Abstract Light-induced degradation in realgar (arsenic sulfide) has been studied by means of four-circle single-crystal X-ray diffraction and X-ray photoelectron spectroscopy. Because of the alteration of realgar exposed to light, the a lattice parameter and c sinβ value increase linearly from 9.327 to 9.385 Å and fro|m 6.320 to 6.364 Å, respectively. In contrast, the b lattice parameter remains substantially constant. Anisotropic variations of the lattice parameters engender a continuous increase of the unit-cell volume from 799.5 to 810.4 Å3. Nevertheless, no correlation exists between the continuous increase of the unit-cell volume and the bond distance variations in As4S4 molecules because the As4S4 molecule in the unit cell expands very little during light exposure. The most pronounced change was in the distance between centroids UiAs4S4 cages. The spread of As4S4 intermolecular distances increases continuously from 5.642 to 5.665 Å, which directly affects the unit-cell volume expansion of realgar. In addition, the O1s peak increases rapidly after light exposure. The result substantiates the following reaction proposed by Biudi et al. (2003): 5As4S4 + 3O2 -> 4As4S5 + 2As2O5. That is, realgar is transformed into pararealgar if oxygen exists and produces the As4S5 molecule. The additional S atom contributes to anisotropic expansion for the a and c axes because the direction of the additional S atom points toward [41̅4] in the unit cell. Furthermore, an S atom in the As4S5 molecule is released from one of the equivalent As-S-As linkages in As4S5 which becomes the As4S4 molecular of pararealgar. After the As4S5 molecule is divided into an S atom (radical) and the As4S4 (pararealgar type) molecule, the free S atom is re-attached to another As4S4 (realgar type) molecule, and reproduces an As4S5 molecule. The reproduced As4S5 molecule is again divided into an S atom (radical) and an As4S4 (pararealgar type) molecule. This cycle whereby realgar is indirectly transformed into pararealgar via the As4S5 molecule is promoted by light and repeated during light exposure.

Studies on the Adsorption Property and Structure of Polyamine-Ended Poly(ethylene glycol) Derivatives on a Gold Surface by Surface Plasmon Resonance and Angle-Resolved X-ray Photoelectron Spectroscopy

The adsorption properties and structure of polyamine-ended poly(ethylene glycol) (PEG) derivatives on a flat gold surface were studied by means of surface plasmon resonance (SPR) and X-ray photoelectron spectroscopy (XPS) using PEG(5k)-block-poly[2-(N,N-dimethylamino)ethyl methacrylate](7.5k) [PEG-b-PAMA(5k/7.5k)] and pentaethylenhexamine-ended PEG(5k) [N6-PEG(5k)], which had 48 and 6 amino groups at the omega-end, respectively. The SPR analysis showed that the amount of PEG-b-PAMA(5k/7.5k) adsorbed onto the gold surface was not affected by the change in pH, and the desorption of this copolymer from the surface was not observed upon the addition of a solution at high salt concentration. The angle-resolved XPS (ARXPS) analysis revealed the structure of the PEG-b-PAMA polymer layer constructed on the gold surface: the PAMA segments were concentrated and located at the interface between the PEG layer and the gold surface. On the other hand, in the case of the PEG-graft-PAMA copolymer (PAMA-g-PEG)-modified gold surface, both the PAMA and the PEG segments homogeneously migrated to all regions of the constructed copolymer layer. The adsorbed amounts of N6-PEG(5k) under different pH conditions were constant and 2-3 times higher than those caused by the adsorption of single amino group-terminated PEG(5k) [PEG-NH(2)(5k)] and hydroxyl group-terminated PEG(5k) [PEG-OH(5k)]. The N6-PEG(5k)-modified gold surface showed a higher nonfouling property toward the adsorption of bovine serum albumin compared with the bare and the N6-modified gold surface. These results indicate that polyamine-ended PEGs were strongly immobilized onto the gold surface by polyamine anchors, even though electrostatic interaction between the polyamine and the gold substrate was not the dominant factor in this adsorption event. Furthermore, the formation of an almost complete phase-separated PEG/polyamine layer on the gold surface by polyamine-ended PEGs was strongly suggested.

Initial Soil Formation Processes of Volcanogenous Regosols (Scoriacious) from Miyake‐jima Island, Japan

In the initial soil formation processes of the Volcanogenous Regosols (Scoriacious) from Miyake-jima Island, Japan, the soil profile morphology showed a distinct formation of the A horizon, about 10 cm thick, over C horizons during a period of 125 years. Along with these soil formation processes under the primary succession of vegetation from bare land to mixed forest, the following changes in the soil characteristics were observed of four study sites where soil formation had occurred over a period of 16, 38, 60 and 125 years in scoriacious volcanic materials ejected during each eruption. Whole soil samples of the surface horizon showed that the proportion of the > 2mm fraction decreased and the clay fraction increased. Electron microscopic observation revealed that pores on the scoria surface were newly formed and had expanded with advanced weathering, and that the formation of a weathering zone on the scoria surface (polygonal shape) was more recognized with the passage of time. Soil pH of the surface horizon decreased, and the amount of carbon in the surface samples showed a linear increase with the passage of time. The amounts of exchangeable bases and the CEC value of the surface samples showed comparable increase rates with time. Consequently, the base saturation percentage was kept at about 100% during the 125-year period. It was suggested that the increase in the amounts of exchangeable bases was controlled by the increase in the amounts of soil organic matter accumulated during the initial soil formation processes of Volcanogenous Regosols (Scoriacious).

Hybridization of sugar alcohols into brucite interlayers via a melt intercalation process.

We report the preparation of organic-brucite (BR) hybrids using harmless sugar alcohols (xylitol, XYL, and sorbitol, SOR). Since XYL and SOR are solid materials at room temperature, the hybridization was investigated by comparing two separate methods, hydrothermal treatment and melt mixing. BR-sugar alcohol hybrids were successfully prepared by a melt intercalation method at 175 °C. X-ray diffraction and Fourier transform infrared spectroscopy analyses indicated that organic molecules were intercalated into the brucite layers, overcoming the barrier of hydroxyl bonds between the BR layers. Moreover, X-ray photoelectron spectroscopy and thermal analyses showed that the intercalated materials at 175 °C resulted in the formation of covalent Mg-O-C bond linkages on the interlayer surface of BR.

The Role of Claysphere under the Environmental Condition on the Earth's Surface

The low soil fertility in semi-arid land requires effective soil improvement measures. To elucidate a possible relationship between dominant minerals and organic materials that improves soil fertility in semi-arid land, several experiments is carried out using kaolinite and urea. The reaction rate of urea-kaolinite complex is determined using XPS and XRD. It is confirmed that the intercalated urea is easily released from the structure of urea-kaolinite complex after dissolution experiments. Soil-forming minerals and native organic polymer compounds which contain nitrogen distributes in semi-arid soil. We will carry out a study at semi-arid land whether complexes will be able to support more efficient agricultural productivity and to determine the applicability of the results obtained to low-fertility areas.

Stability fields of several minerals in the conditions of weathering and hydrothermal alteration. Shift of the fields by the changes in water activity and gibbs free energy of formation.

Many thermodynamical interpretations are used in the study of weathering and hydrothermal alteration. In the simulation of the mechanism of alteration, it is necessary to introduce the factors of physical properties. We investigated the changes in the stability fields of several minerals in detail by the introduction of the parameter of pore size. (1) By assuming that the form of pore of rock or mineral is tubular, the pressure condition at the interface between solid and water changes as a function of diameter of the pore. (2) Water activity changes variedly by the given pressure and temperature. Water activity has been obtained as a function of diameter of pore in rock or mineral. (3) When the water activity changes, the stability field of each chemical species shift the phase boundaries (4) The values of thermochemical data, in particular Gibbs free energy of formation, differ with sources, so that the thermodynamical study on weathering and hydrothermal alteration needs the greatest care with respect to the change in water activity. These results are obtained for the system of K2O-Al2O3-SiO2-H2O.

Changes in thermal properties of rock during weathering. (1) Evaluation of specific heat capacity and volumetric heat capacity during rock weathering.

The problem regarding the change in thermal properties has come to occupy an important position in understanding various types of weathering. The present research pursues the evaluation of changes in specific heat capacity and volumetric heat capacity during rock weathering from a different angle. Two relationships for evaluating the changes of specific heat capacity and volumetric heat capacity in rock weathering have been derived theoretically from the values of some physical properties. The changes of specific heat capacity and volumetric heat capacity in rock during natural weathering are evaluated on the basis of the available data of densities, specific gravity, and water content in weathering profile.