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| Titel |
Accumulation and chemical states of radiocesium by fungus Saccharomyces cerevisiae |
| VerfasserIn |
Toshihiko Ohnuki, Fuminori Sakamoto, Naofumi Kozai, Shinya Yamasaki, Qianqian Yu |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250094306
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| Publikation (Nr.) |
 EGU/EGU2014-9711.pdf |
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| Zusammenfassung |
| After accident of Fukushima Daiichi Nuclear Power Plant, the fall-out radiocesium was
deposited on the ground. Filamentous fungus is known to accumulate radiocesium in
environment, even though many minerals are involved in soil. These facts suggest that fungus
affect the migration behavior of radiocesium in the environment. However, accumulation
mechanism of radiocesium by fungus is not understood. In the present study, accumulation
and chemical states change of Cs by unicellular fungus of Saccharomyces cerevisiae have
been studied to elucidate the role of microorganisms in the migration of radiocesium in the
environment.
Two different experimental conditions were employed; one is the accumulation
experiments of radiocesium by S. cerevisiae from the agar medium containing 137Cs and a
mineral of zeolite, vermiculite, smectite, mica, or illite. The other is the experiments using
stable cesium to examine the chemical states change of Cs. In the former experiment, the
cells were grown on membrane filter of 0.45 μm installed on the agar medium. After the
grown cells were weighed, radioactivity in the cells was measured by an autoradiography
technique. The mineral weight contents were changed from 0.1% to 1% of the
medium. In the latter experiment, the cells were grown in the medium containing
stable Cs between 1 mM and 10mM. The Cs accumulated cells were analyzed
by SEM-EDS and EXAFS. The adsorption experiments of cesium by the cells
under resting condition were also conducted to test the effect of cells metabolic
activity.
Without mineral in the medium, cells of S. cerevisiae accumulated 1.5x103 Bq/g from
the medium containing 137Cs of 2.6x102 Bq/g. When mineral was added in the
medium, concentration of 137Cs in the cells decreased. The concentration of 137Cs
in the cells from the medium containing different minerals were in the following
order;
smectite, illite, mica > vermiculite > zeolite. This order was nearly the same as the
inverse of distribution coefficient of mineral for 137Cs in the medium solution. The
concentration of 137Cs in the cells lowered in the medium containing higher mineral content.
These results indicate that radiocesium was competively accumulated in the cells with
minerals in the soil. Higher concentration of stable Cs was accumulated in the cells in the
metabolically active condition than in the resting cells condition. XAFS analyses showed that
the k3-weighted extended-XAFS functions and the radial structural function of Cs
accumulated by the cells in the metabolically active condition were similar to those in
the resting condition, indicating that chemical states of the accumulated Cs were
nearly the same between both conditions. These results indicate that the fungus
accumulates radiocesium by competitively with minerals in the soils, and performs higher
retardation of the migration of Cs in the metabolically active condition than the resting
one.
A part of this study is the results of "Multidisciplinary investigation on radiocesium fate
and transport for safety assessment for interim storage and disposal of heterogeneous waste"
carried out under the Initiatives for Atomic Energy Basic and Generic Strategic Research
by the Ministry of Education, Culture, Sports, Science and Technology of Japan. |
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