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Journal Articles

Impressions of the 3rd Joint Meeting of Japanese Society of Radiation Safety Management and Japan Health Physics Society

Watanabe, Yuki; Tsuji, Tomoya; Hirota, Seiko*; Hokama, Tomonori; Nakajima, Junya; Tsujiguchi, Takakiyo*; Kimura, Tatsuki*; Koike, Hiromi*; Nakamura, Kaori*; Kuwata, Haruka*; et al.

Hoken Butsuri (Internet), 57(1), p.54 - 64, 2022/03

no abstracts in English

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:1 Percentile:6.45(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

Synergy effect of organic acids from plants on mineral dissolution by siderophore-producing bacteria

Kimura, Tatsuki*; Kozai, Naofumi; Sakamoto, Fuminori; Fukutani, Satoshi*; Ikegami, Maiko*

Doboku Gakkai Rombunshu, G (Kankyo) (Internet), 76(7), p.III_375 - III_382, 2020/00

no abstracts in English

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

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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