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Journal Articles

Volatilization of B$$_{4}$$C control rods in Fukushima Daiichi nuclear reactors during meltdown; B-Li isotopic signatures in cesium-rich microparticles

Fueda, Kazuki*; Takami, Ryu*; Minomo, Kenta*; Morooka, Kazuya*; Horie, Kenji*; Takehara, Mami*; Yamasaki, Shinya*; Saito, Takumi*; Shiotsu, Hiroyuki; Onuki, Toshihiko*; et al.

Journal of Hazardous Materials, 428, p.128214_1 - 128214_10, 2022/04

Journal Articles

Ten years after the NPP accident at Fukushima; Review on fuel debris behavior in contact with water

Grambow, B.; Nitta, Ayako; Shibata, Atsuhiro; Koma, Yoshikazu; Utsunomiya, Satoshi*; Takami, Ryu*; Fueda, Kazuki*; Onuki, Toshihiko*; Jegou, C.*; Laffolley, H.*; et al.

Journal of Nuclear Science and Technology, 59(1), p.1 - 24, 2022/01

 Times Cited Count:0 Percentile:0.37(Nuclear Science & Technology)

Journal Articles

Radiocesium in Shiitake mushroom; Accumulation in living fruit bodies and leaching from dead fruit bodies

Guido-Garcia, F.; Sakamoto, Fuminori; David, K.*; Kozai, Naofumi; Grambow, B.

Chemosphere, 279, p.130511_1 - 130511_10, 2021/09

 Times Cited Count:0 Percentile:0(Environmental Sciences)

Cesium (Cs) accumulation by Shiitake was investigated to contribute to the elucidation of radiocesium-cycling mechanisms in forest environments. The results demonstrate that Shiitake non-specifically accumulates Cs while accumulating the essential element K and provide evidence that no selective Cs accumulation (or binding) sites exist within the Shiitake fruit body. Furthermore, the present results show that most accumulated Cs quickly leaches out from the dead fruit body with exposure to water. The leached Cs was largely adsorbable on clay minerals, suggesting that the Shiitake fruit body likely contains Cs in the cation form.

Journal Articles

Effect of bacterial siderophore on cesium dissolution from biotite

Kimura, Tatsuki*; Fukutani, Satoshi*; Ikegami, Maiko*; Sakamoto, Fuminori; Kozai, Naofumi; Grambow, B.*; Yoneda, Minoru*

Chemosphere, 276, p.130121_1 - 130121_7, 2021/08

 Times Cited Count:0 Percentile:0(Environmental Sciences)

The adsorption of cesium (Cs) on biotite and dissolution of Cs from Cs-bearing biotite using a siderophore were investigated aiming to contribute to the elucidation of radiocesium migration mechanisms in the soil environment. Cs was adsorbed on a hardly weathered biotite powder sample. A siderophore was extracted and purified from the bacterial culture medium, and the purified siderophore was used in five consecutive dissolution experiments of the biotite samples. The major components of the biotite (Al, Fe, and Mg) were dissolved almost stoichiometrically, strongly suggesting that the siderophore selectively dissolves the broken edges of the biotite. The Cs adsorbed on the broken edges was dissolved rapidly as the siderophore dissolved the broken edges, and then, the Cs adsorbed on the outer planar surface of the biotite particles was slowly dissolved.

Journal Articles

Adsorption mechanism of ReO$$_{4}$$$$^{-}$$ on Ni-Zn layered hydroxide salt and its application to removal of ReO$$_{4}$$$$^{-}$$ as a surrogate of TcO$$_{4}$$$$^{-}$$

Tanaka, Kazuya; Kozai, Naofumi; Yamasaki, Shinya*; Onuki, Toshihiko; Kaplan, D. I.*; Grambow, B.

Applied Clay Science, 182, p.105282_1 - 105282_8, 2019/12

 Times Cited Count:5 Percentile:57.36(Chemistry, Physical)

In this study, Ni-Zn layered hydroxide salt (LHS) was used for adsorption experiments of ReO$$_{4}$$$$^{-}$$, as a surrogate of TcO$$_{4}$$$$^{-}$$, in aqueous solutions with various initial Re and sodium salt concentrations. The maximum adsorption amount of Re was estimated at 127.7 mg/g (6.86 $$times$$ 10$$^{-4}$$ eq/g) by fitting adsorption isotherm of ReO$$_{4}$$$$^{-}$$ to Langmuir plot. The adsorption of ReO$$_{4}$$$$^{-}$$ at neutral pH was a reversible process by anion exchange, and decreased with increasing Cl$$^{-}$$, NO$$_{3}$$$$^{-}$$ and SO$$_{4}$$$$^{2-}$$ in solution. EXAFS analysis indicated that ReO$$_{4}$$$$^{-}$$ was adsorbed as an outer-sphere complex on Ni-Zn LHS. The Ni-Zn LHS is a more robust adsorbent for ReO$$_{4}$$$$^{-}$$ than the Mg-Al LDH in terms of solution pH and tolerance to competing anions, and may be an effective alternative to the traditional and more limited method of removing aqueous TcO$$_{4}$$$$^{-}$$ by reductive precipitation.

Journal Articles

Study on coordination structure of Re adsorbed on Mg-Al layered double hydroxide using X-ray absorption fine structure

Tanaka, Kazuya; Kozai, Naofumi; Onuki, Toshihiko; Grambow, B.

Journal of Porous Materials, 26(2), p.505 - 511, 2019/04

 Times Cited Count:6 Percentile:50.98(Chemistry, Applied)

In this study, we utilized X-ray absorption fine structure spectroscopy to clarify the coordination structure of Re in Mg-Al LDH as a surrogate of Tc. Adsorption experiments of ReO$$_{4}$$$$^{-}$$ on calcined and uncalcined Mg-Al LDHs were conducted in aqueous solutions with different concentrations of NaCl, NaNO$$_{3}$$, and Na$$_{2}$$SO$$_{4}$$. Calcined Mg-Al LDH showed much higher adsorption than uncalcined one. The adsorption of ReO$$_{4}$$$$^{-}$$ was reversible, and decreased with increasing concentration of competing anions like Cl$$^{-}$$, NO$$_{3}$$$$^{-}$$, or SO$$_{4}$$$$^{2-}$$. Analysis of Re L$$_{III}$$-edge extended X-ray absorption fine structure indicated that ReO$$_{4}$$$$^{-}$$ was adsorbed as an outer-sphere complex on Mg-Al LDH. The observed Re adsorption-desorption behavior, which was sensitive to the presence of competing anions, was consistent with the formation of outer sphere-complex.

Journal Articles

Continuous liquid-liquid extraction of uranium from uranium-containing wastewater using an organic phase-refining-type emulsion flow extractor

Nagano, Tetsushi; Naganawa, Hirochika; Suzuki, Hideya; Toshimitsu, Masaaki*; Mitamura, Hisayoshi*; Yanase, Nobuyuki*; Grambow, B.

Analytical Sciences, 34(9), p.1099 - 1102, 2018/09

 Times Cited Count:11 Percentile:62.95(Chemistry, Analytical)

A previously reported emulsion flow (EF) extraction system does not include a device for refining used solvent. Therefore, the processing of large quantities of wastewater by using the EF extractor alone could lead to the accumulation of wastewater components into the solvent and diminished extraction performance. In the present study, we have developed a solvent-washing-type EF system, which is equipped with a unit for washing used solvent to prevent accumulation, and successfully applied it for treating uranium-containing wastewater.

Journal Articles

Complexation of Eu(III), Pb(II), and U(VI) with a ${{it Paramecium}}$ glycoprotein; Microbial transformation of heavy elements in the aquatic environment

Kozai, Naofumi; Sakamoto, Fuminori; Tanaka, Kazuya; Onuki, Toshihiko; Sato, Takahiro*; Kamiya, Tomihiro*; Grambow, B.

Chemosphere, 196, p.135 - 144, 2018/04

 Times Cited Count:2 Percentile:13.2(Environmental Sciences)

Transformation of heavy elements by microbes such as bacteria and fungi has been an intense research subject; however, little is known about that of protozoa. This study investigated interaction of a representative protozoa, ${{it Paramecium}}$, with heavy elements (Eu(III), Pb(II), U(VI)). Non-destructive elemental analysis by micro-PIXE hardly detected those elements on living cells after sorption experiments but clearly detected on the cells that were killed with a fixative beforehand. Chromatographic analysis of aquatic species of those heavy elements after the sorption experiments revealed a fraction of those elements bound to a glycoprotein dissolved from the cell surface of living ${{it Paramecium}}$ cells to form soluble pseudocolloid. These findings suggest that complexation of heavy elements with the dissolved surface glycoprotein reduced the sorption of those heavy elements on living cells.

Oral presentation

Development of accumulation technic of $$^{137}$$Cs using mushroom mycelium and minerals

Sakamoto, Fuminori; Kozai, Naofumi; Tanaka, Kazuya; Grambow, B.*

no journal, , 

Six years have passed since the Fukushima Daiichi Nuclear Power accident. However, the decontamination of the forest area remains almost untouched. To develop an effective decontamination method for Fukushima forest soils, we first devised the method to estimate radioactivity of Cs-137 accumulated in fungal mycelium through testing Cs-137 accumulation by about 1500 strains of fungi and then prepared a flat decontamination bag composed of nutrient media, the fungal mycelium with a high Cs-137 accumulation efficiency, and a mixture of zeolite, vermiculite and phlogopite. The decontamination bag accumulated Cs-137 from the contaminated soil in Fukushima forest. Without the minerals, the accumulated Cs-137 was released to the environment after the death of the mycelium. By the addition of the minerals, the Cs-137 in the mycelium was stably fixed by the minerals after the death of the mycelium.

Oral presentation

Accumulation of $$^{137}$$Cs by shiitake cultivated in mushroom bed

Guido-Garcia, F.; Kozai, Naofumi; Sakamoto, Fuminori; Grambow, B.

no journal, , 

We aimed to improve the understanding of the mechanisms by which mushrooms can accumulate radiocesium within the fruit body.Cesium-137 is one of the most common fission products of uranium in nuclear reactors and was widely spread during the Fukushima incident in 2011. Nowadays, $$^{137}$$Cs is one of the main concerns in terms of contamination due to its half-life (30.1 y) and prevalence in forests. Here, cesium is accumulated by different organisms such as animals, plants and fungi. Specifically for fungi, some species have been identified that can accumulate $$^{137}$$Cs efficiently. Mushrooms are of special interest because the ingestion of contaminated species can lead to internal exposure of radioactivity. In this context, understanding the mechanisms by which cesium is accumulated by mushrooms is of particular interest and not yet fully understood. Moreover, the mechanisms by which $$^{137}$$Cs is released back into soil after mushrooms die has not been fully investigated either. In this research, we aim to improve the understanding of $$^{137}$$Cs uptake by comparing its behavior to another cation (K). For this, shiitake mushrooms were used as a model organism and exposed to $$^{137}$$Cs and K under laboratory conditions. Samples of fruit body were taken at different time points and their radioactivity analyzed by Ge detector to evaluate the uptake at different maturity stages. The results of these experiments will be shown and discussed.

Oral presentation

Analysis of $$^{137}$$Cs accumulated ${it Amanita caesareoides}$ in Fukushima

Sakamoto, Fuminori; Kozai, Naofumi; Guido-Garcia, F.; Grambow, B.

no journal, , 

Much $$^{137}$$Cs derived from Fukushima Daiichi Nuclear Power Plant is still staying in the forest area in Fukushima. As a part of elucidation study of the $$^{137}$$Cs circulation mechanism in a forest, we measured $$^{137}$$Cs radioactivity of egg mushrooms (${it Amanita caesareoides}$) which growth wild in Kawamata city in Fukushima at the each growth stages (egg like state, immaturity, maturity, after maturity) and each parts (pileus and stem). As a result, we confirmed they accumulate $$^{137}$$Cs at the stage egg and mature more than the other stages. It is difficult to estimate exactly because the immature sample was slightly one. The radioactivity of $$^{137}$$Cs in the samples after maturity decreased. It is suggested that they release again as a fruit bodies die. As the result of comparison of $$^{137}$$Cs radioactivity in the pileus and stem, pileus accumulates $$^{137}$$Cs more than stem.

Oral presentation

Organic acids production as a possible mechanism of uptake of $$^{137}$$Cs by mushrooms

Guido-Garcia, F.; Sakamoto, Fuminori; Kozai, Naofumi; Grambow, B.

no journal, , 

$$^{137}$$Cs was released from FNPP in 2011 and is one of the main concerns due to its half-life and prevalence in forests. Here, Cs can be taken and accumulated by different organisms, e.g. mushrooms. This can result in mobilization through the environment. Elucidating the mechanisms by which cesium is taken from soil by mushrooms is key to understand its environmental behavior. In soil, Cs can be tightly fixed to clay minerals thus its bioavailability is poor. Organic acids and siderophores produced by mushrooms may remove Cs from mineral surfaces making it bioavailable. To assess this, different strains of fungi were chosen from a ~1000 collection that has been previously tested for Cs accumulation capacity. Organic acids were analyzed by GC-MS and HPLC-ICP-MS from different strains with different accumulating capacities. These were then tested in cesium desorption experiments using key minerals, and compared to a commercial siderophore.

Oral presentation

Study on relations of $$^{137}$$Cs accumulation and species of mushroom, and proteins expressed under $$^{137}$$Cs existence

Sakamoto, Fuminori; Guido-Garcia, F.; Kozai, Naofumi; Tanaka, Kazuya; Grambow, B.

no journal, , 

The radiocesium becomes the stress for creatures, but it is known that some plants and fungi collect radiocesium. We continue a study using a mushroom for the purpose of decontamination of the radiocesium by microbes. We tried to confirm species specificity, expressed proteins and so on to elucidate the mechanism of accumulation of radiocesium by mushroom. As a result, we identified 10 species that accumulate $$^{137}$$Cs as a high rate and another 10 species that accumulate $$^{137}$$Cs as a low rate. We checked the specificity of species, but any tendencies, regularity and specificity were not discovered. We only confirmed the tendency that high accumulated species need a long culture period and low accumulated species need not a long culture period. As a result of two-dimensional electrophoretic analysis, we specified 4 kinds of proteins which express under $$^{137}$$Cs existence and 5 kinds of proteins which disappeared under $$^{137}$$Cs absence.

Oral presentation

Upward migration of radiocesium in soil via abiotic process

Sakamoto, Fuminori; Kozai, Naofumi; Guido-Garcia, F.; Kimura, Tatsuki; Grambow, B.

no journal, , 

Soil microorganisms are known to remove a fraction of tightly fixed radiocesium and make it bioavailable. In this study, we attempted to nondestructively recover available radiocesium from soil using microorganisms instead of plants. Microbial activity was tested to form bioavailable radiocesium by the comparing the addition of nutrients and microbicide. Powdered minerals, a water absorbent material, and paper towels were packed in a fine mesh cloth bag (mineral bag) with a size of 50 cm $$times$$ 50 cm. The radiocesium concentration analysis revealed that the surface soil contained approximately 0.3-1.2 Bq/g. The mineral mat was replaced with a new one every two weeks. Two control experiments were established: one with 1 L of nutrient solution to activate microorganisms, and another with sodium hypochlorite aqueous solution to suppress microbial activity. These solutions were added every week. After eight weeks, radiocesium concentrations of the top soil and in the soil core were measured. The accumulative radiocesium concentration in the four mats after eight weeks was within 4.2$$times$$10$$^{2}$$ and 9.0$$times$$10$$^{2}$$ Bq, indicating that the mats indeed absorbed radiocesium from soil. The driving force of upward migration of radiocesium is thought to be soil water flow due to continuous water absorption from soil by the mat and evaporation from itself. These results suggest that cesium upward migration flow along with water is a behavior expected to happen in the environment.

Oral presentation

Clay mineral dissolution by activities of siderophore producing bacteria

Kimura, Tatsuki; Guido-Garcia, F.; Kozai, Naofumi; Zhang, S.*; Yamaji, Keiko*; Yu, Q.*; Grambow, B.

no journal, , 

To understand bacterial ability to dissolve clay minerals, we isolated siderophore-producing bacteria from white clover roots grown in south Osaka, Japan. The ability to produce siderophores was evaluated by CAS plate method. llite, biotite, vermiculite and nontronite were used for testing as clay minerals. Three different bacteria strains were cultivated. Bacteria cells were centrifuged and washed before inoculation tests. Fifty mg dry weight of bacteria were inoculated into 100 mL modified Balland media and 100 mg of each clay mineral added. The suspension was sampled and new media was added. The concentrations of iron, aluminium and silicon were determined by ICP-OES. The presence of organic molecules was determined by SEC-ICP-OES. The peaks of siderophores were determined using the 405 nm absorbance. As a result, siderophore producing bacteria are able to dissolve clay. This suggests that the effect of siderophore on cesium dissolution is an indirectly process.

Oral presentation

$$^{137}$$Cs uptake by lentinula edodes (shiitake) mushrooms

Guido-Garcia, F.; Sakamoto, Fuminori; Kozai, Naofumi; Grambow, B.; Devid, K.*

no journal, , 

The uptake of Cs by fungi has been thought to be similar to the uptake of K due to their chemical similarities. In this research we aimed to evaluate the impact of different concentrations of K in Cs uptake during mushrooms growth, as well as determine the spatial distribution of both within fruit bodies. Lentinula edodes (shiitake) was used as a model organism due to their capacity to produce fruit body. Preliminary results have shown that the concentrations of $$^{137}$$Cs in the obtained mushroom samples from mushroom bed did not show any clear relationship to the different concentrations of added K. Higher concentrations of $$^{137}$$Cs were observed in pileus than in stem, consistently. The results of Cs and K mapping did not show a significant spatial variation. This result suggest that Cs and K are distributed evenly, and that there is no specific or selective binding site for cesium.

Oral presentation

Ba AND Sr adsorption on microbially formed Mn oxide; Implication to removal of Ra from U mining wastewater

Tanaka, Kazuya; Kozai, Naofumi; Yamaji, Keiko*; Masuya, Hayato*; Grambow, B.

no journal, , 

Radium-226, a descendant nuclide of $$^{238}$$U, is of serious concern in Ningyo-toge Environmental Engineering Center because its radioactive concentration in mining wastewater exceeds the effluent standard. In this study, we examined Ba and Sr adsorption on biogenic Mn oxide as a preliminary surrogate for Ra adsorption. Both Ba and Sr show the dependence of adsorption on NaCl concentration. Overall, Ba gave an order of magnitude higher Kd values than Sr. Adsorption behavior of Ra would be similar to that of Ba in terms of ionic radius. Barium showed Kd value greater than 10$$^{5}$$ in 10 mM NaCl solution, similar to the ionic strength of the fresh water system in the Ningyo-toge center. Therefore, it is expected that the biogenic Mn can work effectively for removal of Ra from mining wastewater.

Oral presentation

Adsorption of Ba and Sr on Mn oxide produced by Coprinopsis urticicola strain Mn-2

Tanaka, Kazuya; Kozai, Naofumi; Yamaji, Keiko*; Masuya, Hayato*; Grambow, B.

no journal, , 

Radium-226 is of serious concern in Ningyo-toge Environmental Engineering Center because its radioactive concentration in mining wastewater exceeds the effluent standard. In this study, we examined Ba and Sr adsorption on biogenic Mn oxide as a preliminary surrogate for Ra adsorption. Both Ba and Sr show the dependence of adsorption on NaCl concentration. Overall, Ba gave an order of magnitude higher Kd values than Sr. Adsorption behavior of Ra would be similar to that of Ba in terms of ionic radius. Barium showed Kd value greater than 10$$^{5}$$ mL/g in 10 mM NaCl solution, similar to the ionic strength of the fresh water system in the Ningyo-toge center. Therefore, it is expected that the biogenic Mn can work effectively for removal of Ra from mining wastewater.

Oral presentation

Accumulation of radiocesium by fungi; Implication for radiocesium circulation in forest

Guido-Garcia, F.; Kimura, Tatsuki*; Sakamoto, Fuminori; Kozai, Naofumi; David, K.*; Grambow, B.*; Haruma, Toshikatsu; Yamaji, Keiko*

no journal, , 

Mushrooms (fungi) accumulate radiocesium from soil and believed to control Cs circulation in forest. To elucidate mechanism of fungi-involving radiocesium circulation in forest, we investigated dissolution of mineral by a fungus mycelia (Phlebiopsis gigantean) and local concentration ratios of cesium to potassium, Cs/K, in fruit body of Lentinula edodes (shiitake). The tested fungus has higher ability than a siderophore-producing bacterium to dissolve minerals. Most of the Fe dissolved from minerals were found to be not stable complexes with organic substances. Cs/K values were almost constant in same fruit body specimen of shiitake, revealing that cesium is stored in proportion to potassium at any locations of a shiitake fruit body and there is no specific binding site for cesium in shiitake.

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