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Journal Articles

Radiocesium distribution of above- and under-ground parts of wild vegetable (${it Eleutherococcus sciadophylloides}$).

Ito, Satomi; Sasaki, Yoshito; Niizato, Tadafumi; Watanabe, Takayoshi; Mitachi, Katsuaki*

KEK Proceedings 2019-2, p.132 - 137, 2019/11

no abstracts in English

Journal Articles

Temporal change of radiocesium loss in a decontaminated deciduous broad-leaved forest

Watanabe, Takayoshi; Sasaki, Yoshito; Niizato, Tadafumi; Mitachi, Katsuaki*; Ito, Satomi

KEK Proceedings 2019-2, p.114 - 119, 2019/11

no abstracts in English

Journal Articles

Amount of radioactive cesium sedimentation in a soil saving dam with 3D laser scanner

Watanabe, Takayoshi; Oyama, Takuya; Ishii, Yasuo; Niizato, Tadafumi; Abe, Hironobu; Mitachi, Katsuaki; Sasaki, Yoshito

KEK Proceedings 2017-6, p.122 - 126, 2017/11

no abstracts in English

Journal Articles

Translocation of radiocesium released by the Fukushima Daiichi Nuclear Power Plant accident in Japanese chestnut and chestnut weevil larvae

Sasaki, Yoshito; Ishii, Yasuo; Abe, Hironobu; Mitachi, Katsuaki; Watanabe, Takayoshi; Niizato, Tadafumi

The Horticulture Journal, 86(2), p.139 - 144, 2017/04

To examine the translocation of radiocesium (Cs) scattered by the Fukushima Daiichi Nuclear Power Plant accident that occurred in March 2011 to the Japanese chestnut, we investigated the autoradiography and radiocesium concentration in each part of the Japanese chestnut. The Japanese chestnut fruit has a thin skin between the kernel (cotyledons) and shell; the kernel of the fruit is edible. $$^{137}$$Cs concentration in each part of the fruit was found to be almost the same at about 1.0$$times$$10$$^{4}$$ Bq$$cdot$$kg$$^{-1}$$. Radiocesium concentration in chestnut weevil larvae found on the fruit was approximately one-seventh of that in the kernel.

Journal Articles

The Transfer of radiocesium from the bark to the stemflow of chestnut trees (${it Castanea crenata}$) contaminated by radionuclides from the Fukushima Dai-ichi Nuclear Power Plant accident

Sasaki, Yoshito; Abe, Hironobu; Mitachi, Katsuaki; Watanabe, Takayoshi; Ishii, Yasuo; Niizato, Tadafumi

Journal of Environmental Radioactivity, 161, p.58 - 65, 2016/09

AA2015-0311.pdf:1.93MB

 Times Cited Count:8 Percentile:35.83(Environmental Sciences)

We report the behavior of radiocesium on the tree bark and its transfer into the stemflow of chestnut in a forest in Fukushima. The radiocesium concentration is greatest in $$phi$$2-cm stem, less in $$<$$$$phi$$5-mm stem, and least in the leaves. In the $$phi$$2-cm stem, the radiocesium concentration of the bark was approximately 10 times that of wood. The average Cs-137 concentration of the dissolved fraction of stem flow was about 10 Bq/L; the pH was nearly constant at 5.8. A strong positive correlation was observed between the radiocesium concentration and the electrical conductivity of the dissolved fraction of stemflow; this result suggests that radiocesium and electrolytes have the same elution mechanism from the tree. Some of the particles in the particulate fraction of the stem flow was strongly adsorbed radiocesium.

Journal Articles

Input and output budgets of radiocesium concerning the forest floor in the mountain forest of Fukushima released from the TEPCO's Fukushima Dai-ichi Nuclear Power Plant accident

Niizato, Tadafumi; Abe, Hironobu; Mitachi, Katsuaki; Sasaki, Yoshito; Ishii, Yasuo; Watanabe, Takayoshi

Journal of Environmental Radioactivity, 161, p.11 - 21, 2016/09

 Times Cited Count:24 Percentile:73.09(Environmental Sciences)

Estimations of radiocesium input and output budgets concerning the forest floor in a mountain forest region have been conducted in the north and central part of the Abukuma Mountains of Fukushima, after 2 to 3 year period following the TEPCO Fukushima Dai-ichi Nuclear Power Plant accident. The radiocesium input and output associated with surface washoff, throughfall, stemflow, and litterfall processes at the experimental plots have been monitored on a forest floor of evergreen Japanese cedar and deciduous Konara oak forests. The results at both monitoring locations show the radiocesium input to be 4-50 times higher than the output during the rainy season in Fukushima. These results indicate that the radiocesium tend to be preserved in the forest ecosystem due to extremely low output ratios. Thus, the associated fluxes throughout the circulation process are key issues for the projecting the environmental fate of the radiocesium levels.

Journal Articles

Biogeochemical signals from deep microbial life in terrestrial crust

Suzuki, Yohei*; Konno, Yuta*; Fukuda, Akari*; Komatsu, Daisuke*; Hirota, Akinari*; Watanabe, Katsuaki*; Togo, Yoko*; Morikawa, Noritoshi*; Hagiwara, Hiroki; Aosai, Daisuke*; et al.

PLOS ONE (Internet), 9(12), p.e113063_1 - e113063_20, 2014/12

 Times Cited Count:9 Percentile:36.08(Multidisciplinary Sciences)

We present multi-isotopic evidence of microbially mediated sulfate reduction in a granitic aquifer, a representative of the terrestrial crust habitat. Deep groundwater of meteoric origin was collected from underground boreholes drilled into the Cretaceous Toki granite, central Japan. A large sulfur isotopic fractionation of 20-60 permil diagnostic to microbial sulfate reduction is associated with the investigated groundwater containing sulfate below 0.2 mM. In contrast, a small carbon isotopic fractionation ($$<$$ 30 permil) is not indicative of methanogenesis. Our results demonstrate that the deep biosphere in the terrestrial crust is metabolically active and playing a crucial role in the formation of reducing groundwater even under low energy fluxes.

Journal Articles

Antiferromagnetic bipolar semiconductor LaMnPO with ZrCuSiAs-type structure

Yanagi, Hiroshi*; Watanabe, Takumi*; Kodama, Katsuaki; Iikubo, Satoshi*; Shamoto, Shinichi; Kamiya, Toshio*; Hirano, Masahiro*; Hosono, Hideo*

Journal of Applied Physics, 105(9), p.093916_1 - 093916_8, 2009/05

 Times Cited Count:42 Percentile:82.64(Physics, Applied)

Electronic and magnetic properties of a layered compound LaMnPO are examined in relation to a newly discovered iso-structural superconductor LaFeAs(P)O. Neutron diffraction measurements, together with temperature dependent magnetic susceptibility, clarify that LaMnPO is an antiferromagnet at least up to 375 K. The spin moment of a Mn ion is determined to be 2.26 $$mu_{B}$$ at room temperature, and the spin configuration is antiparallel in the Mn-P plane and parallel to between the Mn-P planes, which is rather different from that of LaFeAsO. Optical absorption spectra, photoemission spectra, and temperature dependent electrical conductivity indicate that LaMnPO is a semiconductor. Furthermore, nominally undoped LaMnPO exhibits $$n$$-type conduction while the conduction type is changed by doping of Cu or Ca to the La sites, indicating that LaMnPO is a bipolar conductor. Density functional calculation using the GGA+U approximation supports the above conclusions; the electronic band structure has an open band gap and the antiferromagnetic spin configuration is more stable than the ferromagnetic one.

Journal Articles

Ablation-initiated isotope-selective atomic absorption spectroscopy of lanthanide elements

Miyabe, Masabumi; Oba, Masaki; Iimura, Hideki; Akaoka, Katsuaki; Maruyama, Yoichiro; Wakaida, Ikuo; Watanabe, Kazuo

AIP Conference Proceedings 1104, p.30 - 35, 2009/03

no abstracts in English

JAEA Reports

Resonance absorption spectroscopy for laser-ablated lanthanide atom, 1; Optimized experimental conditions for isotope-selective absorption of gadolinium (Contract research)

Miyabe, Masabumi; Oba, Masaki; Iimura, Hideki; Akaoka, Katsuaki; Maruyama, Yoichiro; Wakaida, Ikuo; Watanabe, Kazuo

JAEA-Research 2008-056, 24 Pages, 2008/06

JAEA-Research-2008-056.pdf:5.1MB

For remote isotope analysis of low-decontaminated TRU fuel, we are developing an analytical technique on the basis of the resonance absorption spectroscopy for the laser-ablation plume. To improve isotopic selectivity and detection sensitivity of this technique, we measured absorption spectra of Gd atom with various conditions. As a result, high resolution spectrum was obtained from the observation of slow component of the plume produced under low-pressure rare-gas ambient. The observed narrowest linewidth of about 0.85 GHz was found to be close to the Doppler width estimated for Gd atom of room temperature. Furthermore, relaxation rate of higher meta-stable state was found to be faster than that of ground state, suggesting that use of the transition arising from ground state or lower meta-stable state is preferable for highly sensitive isotope analysis.

Oral presentation

A Study of colloids in deep groundwater using spectroscopic analysis

Yamamoto, Yuhei; Aosai, Daisuke; Mizuno, Takashi; Watanabe, Katsuaki*; Kogure, Toshihiro*; Suzuki, Yohei*

no journal, , 

no abstracts in English

Oral presentation

Mineralogical characterization of colloidal materials suspended in the deep groundwater from the Toki Granite, central Japan

Watanabe, Katsuaki*; Yamamoto, Yuhei; Aosai, Daisuke; Mizuno, Takashi; Takeno, Naoto*; Kogure, Toshihiro*; Suzuki, Yohei*

no journal, , 

no abstracts in English

Oral presentation

The Relation between imaging of soil structure with GPR and depth profile of radioactive cesium

Watanabe, Takayoshi; Mitachi, Katsuaki; Abe, Hironobu; Niizato, Tadafumi

no journal, , 

Radionuclides such as radioactive cesium, now the main radiological contributor, were released in the environment by the Fukushima Dai-ichi Nuclear Power Plant accident. Japan Atomic Energy Agency initiated a project entitled "Long-Term Assessment of Transport of Radioactive Contaminant in the Environment of Fukushima" (F-TRACE project) in November 2012. To understand radioactive cesium transport in forest, we have conducted forest investigation at Ogi district, Kawauchi Village and Yamakiya district, Kawamata Town, Fukushima Prefecture since December 2012. As a part of the investigation, we carried out geophysical exploration of soil structure with ground penetrating radar (GPR) with 100 MHz and 500 MHz radio wave. In this presentation, we report correlation between imaging of soil structure obtained by GPR survey and depth profile of radioactive cesium in soil.

Oral presentation

Forest investigation; Monitoring of surface runoff and downward movement of soil (soil loss), 2

Abe, Hironobu; Ishii, Yasuo; Niizato, Tadafumi; Mitachi, Katsuaki; Watanabe, Takayoshi; Sasaki, Yoshito

no journal, , 

no abstracts in English

Oral presentation

Environmental dynamics of radiocaesium and its outflow flux in the mountain forest; Abukuma Mountains, Fukushima

Niizato, Tadafumi; Abe, Hironobu; Ishii, Yasuo; Watanabe, Takayoshi; Mitachi, Katsuaki

no journal, , 

Environmental dynamics of radiocaesium and its outflow flux are crusial issues for the remediation of the Fukushima environment affected by contamination of the fall out of Fukushima Daiichi Nuclear Power Plant Accident. This paper presents the current status of field investigation and monitoring related to the dynamics and outflow flux of radiocaesium in the mountation forest, Abukuma Mountains, Fukushima, Japan.

Oral presentation

Estimates of a sediment yield sedimentation rate and a outflow variation of radioactive Cs in an erosion control dam with 3D laser scanner

Watanabe, Takayoshi; Oyama, Takuya; Ishii, Yasuo; Niizato, Tadafumi; Abe, Hironobu; Mitachi, Katsuaki; Sasaki, Yoshito; Kitamura, Akihiro

no journal, , 

For an estimate of movement from forest to living spheres, it is important to understand value of movement of soil and radioactive Cs from forest. We measured volumes of deposit with 3D laser scanner in an erosion control dam in Namie town, Fukushima prefecture on August 29, 2013 and December 3, 2014. As a result of measurement, an amount of increase of sediment for 15 months is 0.5 m$$^{3}$$. A denudation rate is 0.02 mm/year. This value is on the same level with denudation rates in meadows and forest, 10$$^{-2}$$ $$sim$$ 10$$^{-1}$$ mm/year (Fujiwara et al, 1999). And it is estimated that a variation of radioactive Cs is Cs-137: 200 MBq, Cs-134: 80 MBq.

Oral presentation

Temporal changes of radiocesium outflow in mountainous forest of the Abukuma Mountains, Fukushima

Niizato, Tadafumi; Abe, Hironobu; Mitachi, Katsuaki; Ishii, Yasuo; Sasaki, Yoshito; Watanabe, Takayoshi; Kitamura, Akihiro; Yamaguchi, Masaaki

no journal, , 

This paper presents outflow characteristics of Cs-137 in mountainous forest of the Abukuma Mountains, Fukushima, during 2013-2014. Cs-137 deposition via throughfall, stemflow, and litterfall processes was estimated to be on the order of 10$$^{3}$$ Bq m$$^{-2}$$, and the outflow of Cs-137 via surface washoff was estimated to be on the order of 10$$^{2}$$ Bq m$$^{-2}$$ from April 2013 to December 2014 in the experimental plots installed in deciduous broad-leaved and cedar forests in the Abukuma Mountains. Cs-137 inventories of forest soil down to a level of 1 cm were decreasing in ridge and valley-bottom soil during the period from December 2012 to October 2014. The inventories in mountain slope showed both decreasing and increasing tendencies because of the heterogeneous transportation of Cs-137 via surface washoff on the slope. The results of outflow rate simulations using the SACT model developed in the Japan Atomic Energy Agency indicate decreasing tendency accompanied with a deeper penetration of Cs-137 into soil profile. Thus, the forest floor in the mountainous forest seems to be a sink of radiocesium contamination rather than a source for the contamination of the other ecosystems.

Oral presentation

Changes in the concentrations of radioactive cesium outflowed from the steep mountainous forest of Abukuma Mountains, released by Fukushima Daiichi Nuclear Power Plant accident

Ishii, Yasuo; Watanabe, Takayoshi; Oyama, Takuya; Sasaki, Yoshito; Abe, Hironobu; Mitachi, Katsuaki; Niizato, Tadafumi

no journal, , 

Mountainous forest is currently one of the most important sources of radioactive cesium released from the Fukushima Daiichi Nuclear Power Plant accident in Fukushima prefecture, which was covered approximately 70% of the land area by the forest. This study reports the changes in concentrations of radioactive cesium in sediments outflowed from the steep mountainous forest of the Abukuma Mountains, Fukushima, during September - December 2015.

Oral presentation

Installation of observation device for soil loss in a decontaminated forest

Watanabe, Takayoshi; Ishii, Yasuo; Niizato, Tadafumi; Sasaki, Yoshito; Mitachi, Katsuaki*

no journal, , 

no abstracts in English

Oral presentation

Estimate of variation of radioactive cesium sedimentation in a soil saving dam with the 3D laser scanner

Watanabe, Takayoshi; Oyama, Takuya; Ishii, Yasuo; Niizato, Tadafumi; Abe, Hironobu; Mitachi, Katsuaki; Sasaki, Yoshito

no journal, , 

no abstracts in English

27 (Records 1-20 displayed on this page)