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Okumura, Masahiko; Nakamura, Hiroki; Machida, Masahiko
no journal, ,
Radiocesium was provided into an environment by the Fukushima Nuclear Power Plant accident and is mainly retained by surface soil. In the top soil, micaceous clay minerals adsorb radiocesium strongly. Particularly, it is known that the edge parts of them show selective adsorption of cesium when the density of cesium is low. We made a simple model using density functional theory to investigate this chemical reaction. In a high density case, it is known that serial adsorption of cesium is occurred. We found that serial adsorption is realistic process in this case. In both cases, competition between the interlayer distance of clay minerals and ion radius of cesium plays critical role on adsorption chemical reaction. This interpretation is consistent with several experimental results. These results give fundamental information about microscopic adsorption reaction of cesium adsorption by micaceous clay minerals.
Onuki, Toshihiko
no journal, ,
We have conducted the research on the interaction of REEs with microorganisms. The adsorbed REEs on the cell surface changed the chemical states to the REEs-phosphate precipitates. Genes concerned with phosphate transport contribute to uranium tolerance, suggesting that REE- and U(VI)-phosphate precipitations are resulted from the expression of yeast by the adsorption of REE and U(VI). We found distinct organic molecules released from Mn oxidizing fungus, which complexed selectively with tetra valent elements including Ce and Th.
Obata, Hajime*; Miwa, Kazuji*; Kondo, Yoshiko*; Gamo, Toshitaka*; Otosaka, Shigeyoshi; Suzuki, Takashi
no journal, ,
Distributions chemical species of iodine (iodide, iodate and organic iodine) in seawater were investigated in the Chukchi Sea and Bering Sea, Arctic northern marginal seas. 
I, which is a good tracer for anthropogenically released iodine to the marine environments, were also revealed by this study. Iodide concentrations in seawater often increased toward the seafloor. This tendency was remarkable with iodide and organic iodine, indicating that these iodine species are released from the sediments of the continental shelf. Concentrations of I ranged from 0.79 to 2.89
10
atom/L. While this level was several times higher than those in the North Pacific, significant increase of I concentration due to seawater inflow from the North Atlantic was not observed. Considering latitudinal range of this study area, it can be estimated that most I detected by this study was derived by atmospheric deposition of I originates from Europe.
reductionKato, Tomoaki; Onuki, Toshihiko; Saito, Takumi; Yu, Q.
no journal, ,
Sorption of divalent Co was studied during Mn oxides formation on microbial surface. Permanganate was reduced on the cell surface to form tetravalent Mn oxides. XANES analysis revealed that divalent Co was oxidized to trivalent one during the accumulation to Mn oxides. These results indicate that sorption mechanism of divalent Co by biogenic Mn oxides accompanying oxidative precipitation.
-AlOOH and HD isotope effectSano, Asami; Hattori, Takanori
no journal, ,
-AlOOH is a distorted rutile type hydrous phase. X-ray study have found the change in compressibility at high-pressure, with an isotope effect on the transition pressure. To examine the pressure response of hydrogen bond in -AlOOH and its DH isotope difference, we performed neutron diffraction experiments at high-pressure neutron diffractometer PLANET in MLF, J-PARC. The transition from P21nm to Pnnm, which can be attributed to the disorder of hydrogen bond or the symmtrization was found at 12.1 GPa for -AlOOD, at the same pressure where the change in compressibility was reported. The significant shortening of O...O distance and hydrogen bond was observed to 12.1 GPa; however, the O...O distance remains almost constant above the transition pressure. This study reveals that slight change of hydrogen position can induce the increase of bulk modulus in -AlOOH at high pressure.