恩田 裕一*; 谷口 圭輔*; 吉村 和也; 加藤 弘亮*; 高橋 純子*; 脇山 義史*; Coppin, F.*; Smith, H.*
Nature Reviews Earth & Environment (Internet), 1(12), p.644 - 660, 2020/12
This review, concerning on findings obtained by detailed field monitoring after the Fukushima Daiichi Nuclear Power Plant accident, covers the initial fallout and vertical movement of radionuclide in the land and forest, and subsequent transport and redistribution through hydrological and geomorphological processes in cropland, urban area, paddy field, and forested area. We discuss the finding of the transport of radionuclides through rivers and new discoveries for hydrological and sediment transport environmental impact in monsoonal regions.
恩田 裕一*; 谷口 圭輔*; 吉村 和也; 加藤 弘亮*; 高橋 純子*; 脇山 義史*; Coppin, F.*; Smith, H.*
Nature Reviews Earth & Environment (Internet), 1(12), P. 694_1, 2020/12
The values along the mass depth axes in Figure 4a and 4b were slightly misaligned, and the relaxation mass depth markers shown in Figure 4b and 4c incorrectly located.
谷口 圭輔*; 恩田 裕一*; Smith, H. G.*; Blake, W.*; 吉村 和也; 山敷 庸亮*; 倉元 隆之*
Scientific Data (Internet), 7, p.443_1 - 443_9, 2020/12
Data on radiocesium concentrations and fluxes have been collected in rivers within 80 km of the FDNPP from June 2011, three months after the accident, to the present. That data is available on the web up to March 2017. These data are expected to be widely used for validation of the radiocaesium transport model, comparison between the FDNPP and Chernobyl accidents, influence on the health of residents, and evaluation of the effect of the environmental remediation measures in Fukushima. Therefore, these data set were provided in this data journal.
脇山 義史*; 恩田 裕一*; 吉村 和也; 五十嵐 康記*; 加藤 弘亮*
Journal of Environmental Radioactivity, 210, p.105990_1 - 105990_12, 2019/12
This study provides the results of observations of plot-scale Cs wash-off from various land uses (two uncultivated farmlands, two cultivated farmlands, three grasslands and one forest) from 2011 to 2014. Annual Cs wash-off rate ranged from 0.0026 to 7.5% per year, and more vegetation cover resulted in lower sediment discharge. Cs concentration observed in uncultivated farmland plot decreased with time and the rate was lower than those of riverine, suggesting that contributions of Cs from the upslope area may be insignificant to that in riverine. A negative relationship between Cs concentration normalized by initial deposition amount and sediment concentration in runoff water was found. Cultivation appeared to cause enhanced soil erosion and resulted in constant relatively low Cs concentration. A contribution of coarse organic matter to Cs wash-off was suggested in the forest, which had relatively high Cs concentration and low sediment discharge.
加藤 弘亮*; 恩田 裕一*; Gao, X.*; 眞田 幸尚; 斎藤 公明
Journal of Environmental Radioactivity, 210, p.105996_1 - 105996_12, 2019/12
Ascertaining the initial amount of accidentally released radiocesium is fundamental for determining the extent of radioactive contamination following nuclear accidents, and is of key importance to environmental transfer models. A series of the airborne monitoring surveys of radioactivity have conducted by the Japanese MEXT, and provide basic information on radioactive contamination following the accident. However, there are no clear guidelines regarding the selection of airborne monitoring survey results for estimating the initial fallout input in studies of the environmental transfer of radiocesium. This study reconstructed a fallout map of Fukushima accident-derived radiocesium based on a comparison of the radiocesium deposition densities derived from the third and fifth airborne monitoring surveys.
斎藤 公明; 恩田 裕一*; 久松 俊一*
Journal of Environmental Radioactivity, 210, p.106003_1 - 106003_2, 2019/12
斎藤 公明; 三上 智; 安藤 真樹; 松田 規宏; 木名瀬 栄; 津田 修一; 佐藤 哲朗*; 関 暁之; 眞田 幸尚; Wainwright-Murakami, Haruko*; et al.
Journal of Radiation Protection and Research, 44(4), p.128 - 148, 2019/12
Massive environmental monitoring has been conducted continuously after the Fukushima accident with different monitoring methods having different features together with migration studies of radiocesium in diverse environments. At three months after the accident, multiple radionuclides were detected at many places; while it was confirmed that radiocesium was most important from the viewpoint of long-term exposures. The air dose rates in environments related to human living have decreased faster than expected from radioactive decay by a factor of 2-3 on average. An empirical model for predicting air dose rate distribution was developed based on statistical analysis of massive car-borne survey data. Some trials were performed to integrate different types of contamination maps to obtain an integrated map of better quantity. Annual external exposure doses for residents who would return to their home were estimated to less than a few mSv as a whole. The environmental data and knowledge have been provided for diverse-spectrum of people in different ways.
辻 英樹*; 石井 弓美子*; Shin, M.*; 谷口 圭輔*; 新井 宏受*; 栗原 モモ*; 保高 徹生*; 倉元 隆之*; 中西 貴宏; Lee, S*; et al.
Science of the Total Environment, 697, p.134093_1 - 134093_11, 2019/12
谷口 圭輔*; 恩田 裕一*; Smith, H. G.*; Blake, W.*; 吉村 和也; 山敷 庸亮*; 倉元 隆之*; 斎藤 公明
Environmental Science & Technology, 53(21), p.12339 - 12347, 2019/11
The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident released the largest quantity of radiocesium into the environment since Chernobyl. Here, we show for the first time, how redistribution of radiocesium by river and watershed-scale hydrological processes in Fukushima is driving localized decline in terrestrial dose rates in populated areas. The rate of Fukushima recovery greatly exceeds initial post-disaster expectations and indicates that landscape-scale recovery from such large contamination events is highly dependent on local hydrological and land use controls.
栗原 モモ*; 保高 徹生*; 青野 辰雄*; 芦川 信雄*; 海老名 裕之*; 飯島 健*; 石丸 圭*; 金井 羅門*; 苅部 甚一*; 近内 弥恵*; et al.
Journal of Radioanalytical and Nuclear Chemistry, 322(2), p.477 - 485, 2019/11
Yang, B.*; 恩田 裕一*; 大森 良弘*; 関本 均*; 藤原 徹*; 脇山 義史*; 吉村 和也; 高橋 純子*; Sun, X.*
Science of the Total Environment, 603-604, p.49 - 56, 2017/12
In this study, the effect of topsoil removal measure and fertilizer application on radiocesium uptake by rice plants was investigated over a four-year period. The results indicate that the effect of topsoil removal measure on the accumulation of radiocesium in rice plants was effective. We summarized four year's data to further confirm that potassium and nitrogen fertilizers had an opposite effect on the accumulation of radiocesium in rice plants. Increasing potassium and reducing nitrogen fertilizer conditions tended to inhibit the radiocesium uptake by rice plants.
内山 雄介*; 東 晃平*; 小谷 瑳千花*; 岩崎 理樹*; 津旨 大輔*; 上平 雄基; 清水 康行*; 恩田 裕一*
土木学会論文集,B2(海岸工学)(インターネット), 73(2), p.I_685 - I_690, 2017/10
吉村 和也; 恩田 裕一*; 若原 妙子*
Environmental Science & Technology, 50(8), p.4186 - 4193, 2016/04
Particulate radiocesium concentration in paddy fields was studied for its parameterization and temporal changes over an extensive area covering various deposition levels of radiocesium after the FDNPP accident. The particulate radiocesium concentration in the paddy field correlated with the deposition amounts, indicating that the entrainment coefficient, defined as the ratio of concentration and deposition amounts, is useful for estimating the particulate radiocesium concentration in a paddy field. Variability of the entrainment coefficient was reduced by correcting the particle size dependency of particulate radiocesium concentration. The entrainment coefficient decreased with time according to a double exponential function. The decrease rate constant of the entrainment coefficient was higher than those of other land uses, thus demonstrating a rapid decrease in the particulate radiocesium concentration in the tested paddy field.
Yang, B.*; 恩田 裕一*; 脇山 義史*; 吉村 和也; 関本 均*; Ha, Y.*
Environmental Pollution, 208(Part B), p.562 - 570, 2016/01
In this study, we investigated the temporal changes of radiocesium in soil, irrigation water, and rice plant in two adjacent rice paddies, with and without surface-soil-removal practice, in Fukushima Prefecture for over three years (2012 to 2014). Our results showed that radiocesium migrated into 24-28 cm soil layers and that the concentration and inventory of radiocesium in paddy soils generally decreased. The newly added radiocesium to paddies through irrigation water contributed only the maximum values of 0.15% and 0.75% of the total amount present in normal and decontaminated paddies, respectively, throughout the study period. The change trend of radiocesium concentration in suspended sediment in irrigation water exponentially decreased. Radiocesium accumulation in rice plant also decreased with time in both paddies. However, the transfer factor of radiocesium for rice plant in the decontaminated paddy increased compared with normal paddy.
Konoplev, A.*; Golosov, V.*; Laptev, G.*; 難波 謙二*; 恩田 裕一*; 高瀬 つぎ子*; 脇山 義史*; 吉村 和也
Journal of Environmental Radioactivity, 151(Part 3), p.568 - 578, 2016/01
Comparative analysis is provided for radiocesium wash-off parameters and Kd between suspended matter and water in rivers and surface runoff on Fukushima and Chernobyl contaminated areas for the first years after the accidents. It was found that radiocesium distribution coefficient in Fukushima rivers is essentially higher than those in Chernobyl. This can be associated with two factors: a higher RIP of samples in Fukushima and the presence of water insoluble glassy particles. It was found also that dissolved wash-off coefficients for Fukushima catchments are lower than those in Chernobyl. Particulate wash-off coefficients are comparable for Fukushima and Chernobyl. The radiocesium migration in undisturbed forest and grassland soils at Fukushima has been shown to be faster than those in Chernobyl. Investigation and analysis of radiocesium distribution in soils of Niida river catchment revealed accumulation of contaminated sediments on its floodplain.
斎藤 公明; 谷畑 勇夫*; 藤原 守; 齊藤 敬*; 下浦 享*; 大塚 孝治*; 恩田 裕一*; 星 正治*; 池内 嘉宏*; 高橋 史明; et al.
Journal of Environmental Radioactivity, 139, p.308 - 319, 2015/01
The soil deposition density maps of -ray emitting radioactive nuclides from the Fukushima Daiichi Nuclear Power Plant (NPP) accident were constructed on the basis of the results from large-scale soil sampling. The 10,915 soil samples were collected at 2,168 locations. -rays emitted from the samples were measured by Ge detectors and analyzed using a reliable unified method. The determined radioactivity was corrected to that as of June 14, 2011 by taking into account the intrinsic decay constant of each nuclide. Finally the maps were created for Cs, Cs, I, Te and Ag. The radioactivity ratio of Cs to Cs was almost constant as 0.91 irrelevant to the soil sampling location. Effective doses for 50 years after the accident were evaluated for external and inhalation exposures due to the observed radioactive nuclides. The radiation doses from radioactive cesium were found to be much higher than those from other radioactive nuclides.
吉村 和也; 恩田 裕一*; 加藤 弘亮*
Journal of Environmental Radioactivity, 139, p.362 - 369, 2015/01
Radiocaesium wash-off associated with soil erosion in different land use was monitored using USLE plots in Kawamata, Fukushima Prefecture, Japan after the Fukushima Dai-ichi Nuclear Power Plant accident. Parameters and factors relating to soil erosion and Cs concentration in the eroded soil were evaluated based on the field monitoring and presented. The erosion of fine soil, which is defined as the fraction of soil overflowed along with discharged water from a sediment-trap tank, constituted a large proportion of the discharged radiocaesium. This indicated that the quantitative monitoring of fine soil erosion is greatly important for the accurate evaluation of radiocaesium wash-off. An exponential relationship was found between vegetation cover and the amount of eroded soil. Moreover, the radiocaesium concentrations in the discharged soil were greatly affected by the land use. These results indicate that radiocaesium wash-off related to vegetation cover and land use is crucially important in modelling radiocaesium migration.
吉村 和也; 恩田 裕一*; 坂口 綾*; 山本 政儀*; 松浦 裕樹*
Journal of Environmental Radioactivity, 139, p.370 - 378, 2015/01
An extensive investigation of particulate radiocaesium in suspended solids and dissolved radiocaesium in river water was undertaken at 30 sites in Fukushima and Miyagi Prefectures in December 2012, and their relationships with catchment inventory and the solid/liquid distribution coefficient () were evaluated. Rivers located in the coastal region on the north side of the Fukushima Dai-ichi Nuclear Power Plant exhibited relatively higher particulate radiocaesium concentrations. Significant correlations were found between concentrations of particulate/dissolved radiocaesium and average catchment inventories, indicating that the concentrations of particulate/dissolved radiocaesium could be approximated from the catchment inventory. Particulate radiocaesium concentration was significantly correlated with dissolved radiocaesium concentration (with the exception of concentrations measured in estuaries), and the geometric mean was calculated.
斎藤 公明; 恩田 裕一*
Journal of Environmental Radioactivity, 139, p.240 - 249, 2015/01
福島第一原子力発電所事故の後、国からの委託を受け原子力機構は多くの機関と協力しながらマップ事業を実施してきた。この中で、広域にわたる大規模放射線モニタリングと放射線量率等のマップ作成、環境中における放射線セシウムの移行調査とモデル化等を行なってきた。平成24年度までにマップ事業の中で得られた成果を17編の論文としてまとめ、学術雑誌Journal of Environmental Radioactivityの特集号として発刊する。本稿では、この特集号の序論として、マップ事業の全体計画、スケジュール、各調査項目の位置付け及び主要な成果について紹介する。
吉村 和也; 恩田 裕一*; 福島 武彦*
Scientific Reports (Internet), 4, p.4514_1 - 4514_6, 2014/03
This study used particle size analysis to investigate the initial accumulation and trap efficiency of radiocesium (Cs) in four irrigation ponds, 4-5 months after the Fukushima Dai-ichi Nuclear Power Plant (DNPP) accident. Trap efficiency, represented by the inventory of Cs in pond sediment to the inventory of radiocesium in soil surrounding the pond (i.e., total Cs inventory), was less than 100% for all but one pond. Trap efficiency decreased as sediment particle size increased, indicating that sediments with a smaller particle size accumulate more Cs. In ponds showing low trap efficiency, fine sediment containing high concentrations of Cs appeared to be removed from the system by hydraulic flushing, leaving behind mostly coarse sediment.