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).Ito, Satomi; Sasaki, Yoshito; Niizato, Tadafumi; Watanabe, Takayoshi; Mitachi, Katsuaki*
KEK Proceedings 2019-2, p.132 - 137, 2019/11
no abstracts in English
Watanabe, Takayoshi; Sasaki, Yoshito; Niizato, Tadafumi; Mitachi, Katsuaki*; Ito, Satomi
KEK Proceedings 2019-2, p.114 - 119, 2019/11
no abstracts in English
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
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. 
Cs concentration in each part of the fruit was found to be almost the same at about 1.0
10
Bq
kg
. Radiocesium concentration in chestnut weevil larvae found on the fruit was approximately one-seventh of that in the kernel.
) contaminated by radionuclides from the Fukushima Dai-ichi Nuclear Power Plant accidentSasaki, Yoshito; Abe, Hironobu; Mitachi, Katsuaki; Watanabe, Takayoshi; Ishii, Yasuo; Niizato, Tadafumi
Journal of Environmental Radioactivity, 161, p.58 - 65, 2016/09
Times Cited Count：18 Percentile：43.92(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 
2-cm stem, less in 
5-mm stem, and least in the leaves. In the 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.
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：32 Percentile：66.84(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.
Osawa, Kota*; Niizato, Tadafumi; Mitachi, Katsuaki*; Kawamura, Makoto*; Okawa, Masahiro*
no journal, ,
Primary outflow process of radiocesium, which is released by the TEPCO's Fukushima Dai-ichi Nuclear Power Plant accident, from a forest slope to a mountain stream is a particulate-bond state transport. A detailed estimation of riverbed form and sediment volume changing with time is a key issue to assess the radiocesium distribution in the forested environment. We attempt to restore the three-dimensional structure of underwater riverbed form in the mountain stream from the captured digital images by applying the SfM (Structure from Motion) and MVS (Multi View Stereo) technologies. Discrepancy between measured and analytical results increase with depth, the estimation errors are 73% and 93% in the depth of 20-25 cm and 10-15 cm, respectively. Next step is an improvement of the correction and image-capturing methods to reduce the estimation errors by elimination of the light refraction on the stream water surface.
Sasaki, Yoshito; Niizato, Tadafumi; Mitachi, Katsuaki*; Ito, Satomi; Watanabe, Takayoshi
no journal, ,
no abstracts in English
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.
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
. A denudation rate is 0.02 mm/year. This value is on the same level with denudation rates in meadows and forest, 10
10 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.
Niizato, Tadafumi; Abe, Hironobu; Ishii, Yasuo; Sasaki, Yoshito; Mitachi, Katsuaki; Kitamura, Akihiro; Yamaguchi, Masaaki
no journal, ,
The depth profile of radiocaesium at the mountain forest of Abukuma Mountains, Fukushima Prefecture, shows the decreasing tendency of the radiocaesium inventory in the most upper part of the soil layer at ridge and valley bottom. A very slightly downward infiltration of the radiocaesium was found with decreasing of the inventory near the ground surface but most of the radiocaesium still exist in the upper part of the soil layer. Outflow of the radiocaesium from the mountain forest get to decrease due to the downward infiltration of the radiocaesium in the soil horizon by the application of the SACT model developed in JAEA.
Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Mitachi, Katsuaki*; Watanabe, Takayoshi
no journal, ,
Ito, Satomi; Sasaki, Yoshito; Niizato, Tadafumi; Watanabe, Takayoshi; Mitachi, Katsuaki*
no journal, ,
no abstracts in English
Watanabe, Takayoshi; Sasaki, Yoshito; Niizato, Tadafumi; Mitachi, Katsuaki*; Ito, Satomi
no journal, ,
no abstracts in English
Abe, Hironobu; Ishii, Yasuo; Niizato, Tadafumi; Mitachi, Katsuaki; Watanabe, Takayoshi; Sasaki, Yoshito
no journal, ,
no abstracts in English
Ishii, Yasuo; Mitachi, Katsuaki; Abe, Hironobu; Niizato, Tadafumi
no journal, ,
As part of "Long-Term Assessment of Transport of Radioactive Contaminant in the Environment of Fukushima" (F-TRACE project), JAEA have researched to expect the transportation of radioactive caesium from contaminated mountain forests based on survey data in Fukushima prefecture, and to implement technical information and remedial measures to prevent contamination of decontaminated areas and domestic water supply. In this study, we report characterization and radio assay of the surface run-off substances at forest research plots in Ogi district of Kawauchi-mura and Yamakiya district of Kawamata-machi in 2013-2014, 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 Bq m, and the outflow of Cs-137 via surface washoff was estimated to be on the order of 10
Bq m 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.
Niizato, Tadafumi; Sasaki, Yoshito; Mitachi, Katsuaki*
no journal, ,
The outflow of Cs from the mountainous forest floor was estimated in the Abukuma Mountains, Fukushima. The outflow rates are decreased with a cover rate of the forest floor by a litter layer. The result shows the important role of the litter layer and undergrowth on a migration control of the radiocesium outflow from the forest floor.
Watanabe, Takayoshi; Ishii, Yasuo; Niizato, Tadafumi; Sasaki, Yoshito; Mitachi, Katsuaki*
no journal, ,
no abstracts in English
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.
