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Your search keyword '"Onda, Yuichi"' showing total 43 results
Start Over Author "Onda, Yuichi" Journal journal of environmental radioactivity
43 results on '"Onda, Yuichi"'

36. Differences in leaching characteristics of dissolved radiocaesium and potassium from the litter layer of Japanese cedar and broadleaf forests in Fukushima, Japan

Author

Takada, Momo, Onda, Yuichi, Yasutaka, Tetsuo, and Momo, Takada

Abstract

Cesium is an element that belongs to the same group as K, and is known to show similar behaviour to that of K in plants. In this study, we conducted a serial leaching test for 120 h to compare the leaching characteristics of dissolved 137Cs and K in forest litter, obtained from Japanese cedar and deciduous broadleaf forests located 40 km from the site of the 2011 Fukushima Dai-ichi nuclear power plant accident. The litter was collected in 2018 and was divided into three groups according to the decomposition level. The cumulative leachable fraction of 137Cs at 120 h ranged from 0.3% to 3.3%, suggesting that most of the 137Cs in the litter was hardly leachable in water. The leachable fraction of 137Cs generally decreased with the decomposition level of the litter, implying that the easily leachable 137Cs eluted into the water during the first stage of decomposition. Meanwhile, the cumulative leachable fraction of K at 120 h was approximately 10 times greater than that of 137Cs and ranged from 22.7% to 54.8%. The leaching speeds of 137Cs and K decreased suddenly with elapsed time regardless of the tree species, decomposition degree, or element. Our findings contribute to the long-term understanding of the 137Cs cycle in forest ecosystems.

Published
2020

42. Depth distribution of 137Cs, 134Cs, and 131I in soil profile after Fukushima Dai-ichi Nuclear Power Plant Accident

Author

Kato, Hiroaki, Onda, Yuichi, and Teramage, Mengistu

Subjects
*CESIUM, *TOPSOIL, *TILLAGE, *EARTHQUAKES, *FUKUSHIMA Nuclear Accident, Fukushima, Japan, 2011
Abstract

Abstract: Soil, vegetation and other ecological compartments are expected to be highly contaminated by the deposited radionuclides after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident triggered by a magnitude 9.0 earthquake and the resulting tsunami on 11 March 2011. However, there is no field measurement data on the depth distributions of radiocaesium and 131I concentrations in soil profile. In this study, the depth distribution of the deposited radionuclides in the cultivated soil profile was investigated in one of the most contaminated area after FDNPP accident. The result of this study demonstrated that greater than 86% of total radiocaesium and 79% of total 131I were absorbed in the upper 2.0 cm in the soil profile. The relaxation mass depth (h 0) derived from the depth distribution of radiocaesium and 131I in the soil profile at the study site were 9.1 kg m−2 and 10.4 kg m−2, respectively. The h 0 of 137Cs in the studied soil profile was greater than those for the cultivated soils nearby the Chernobyl NPP. The positive relationship was found between clay content of topsoil and the h 0 of 137Cs. However, further analysis is required to clarify the effect of clay content on the initial penetration depth of deposited 137Cs in soil profile. [Copyright &y& Elsevier]

Published
2012
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43. Environmental mobility of 110mAg: lessons learnt from Fukushima accident (Japan) and potential use for tracking the dispersion of contamination within coastal catchments.

Author

Lepage, Hugo, Evrard, Olivier, Onda, Yuichi, Patin, Jeremy, Chartin, Caroline, Lefèvre, Irène, Bonté, Philippe, and Ayrault, Sophie

Subjects
*FUKUSHIMA Nuclear Accident, Fukushima, Japan, 2011, *DISPERSION (Atmospheric chemistry), *COASTAL engineering, *INDUSTRIAL contamination, *SILVER, *METASTABLE states, *ANTHROPOGENIC soils, *RADIOISOTOPES
Abstract

Abstract: Silver-110 metastable (110mAg) has been far less investigated than other anthropogenic radionuclides, although it has the potential to accumulate in plants and animal tissues. It is continuously produced by nuclear power plants in normal conditions, but emitted in much larger quantities in accidental conditions facilitating its detection, which allows the investigation of its behaviour in the environment. We analysed 110mAg in soil and river drape sediment (i.e., mud drapes deposited on channel-bed sand) collected within coastal catchments contaminated in Fukushima Prefecture (Japan) after the Fukushima Dai-ichi Nuclear Power Plant accident that occurred on 11 March 2011. Several field experiments were conducted to document radiosilver behaviour in the terrestrial environment, with a systematic comparison to the more documented radiocesium behaviour. Results show a similar and low mobility for both elements in soils and a strong affinity with the clay fraction. Measurements conducted on sediment sequences accumulated in reservoirs tend to confirm a comparable deposition of those radionuclides even after their redistribution due to erosion and deposition processes. Therefore, as the 110mAg:137Cs initial activity ratio varied in soils across the area, we justified the relevance of using this tool to track the dispersion of contaminated sediment from the main inland radioactive pollution plume generated by FDNPP accident. [Copyright &y& Elsevier]

Published
2014
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