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論文

Correction to Transport and redistribution of radiocesium in Fukushima fallout through rivers

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, 55(13), P. 9394, 2021/07

 被引用回数:0 パーセンタイル:0.53(Engineering, Environmental)

下記、投稿論文の修正 "Transport and redistribution of radiocesium in Fukushima fallout through rivers, 2019. Environmental Science and Technology, 53, 12339-12347"

論文

Observation of longitudinal magnetic fluctuations at a first-order ferromagnetic quantum phase transition in UGe$$_2$$

野間 雄一郎*; 小手川 恒*; 久保 徹郎*; 藤 秀樹*; 播磨 尚朝*; 芳賀 芳範; 山本 悦嗣; 大貫 惇睦*; 伊藤 公平*; 仲村 愛*; et al.

Journal of the Physical Society of Japan, 90(7), p.073707_1 - 073707_5, 2021/07

 被引用回数:0 パーセンタイル:0(Physics, Multidisciplinary)

Ferromagnetic fluctuation relevant to the pressure-induced superconductivity in UGe$$_2$$ is investigated by means of NMR spectroscopy. Longitudinal magnetic fluctuations were observed in the spin-echo decay rate near the ferromagnetic critical point where superconductivity takes place. This result strongly suggests that superconductivity in ferromagnets is universally mediated by anisotropic magnetic fluctuations.

論文

Impacts of freeze-thaw processes and subsequent runoff on $$^{137}$$Cs washoff from bare land in Fukushima

五十嵐 康記*; 恩田 裕一*; 脇山 義史*; 吉村 和也; 加藤 弘亮*; 小塚 翔平*; 馬目 凌*

Science of the Total Environment, 769, p.144706_1 - 144706_9, 2021/05

 被引用回数:0 パーセンタイル:0(Environmental Sciences)

The impact of freeze-thaw processes and subsequent runoff affecting the Cs-137 ($$^{137}$$Cs) flux and concentration in sediment discharge were revealed in bareland erosion plot following the Fukushima Nuclear Power Plant accident by detailed monitoring and laser scanner measurement on the soil surface. We found that surface topographic changes due to the frost-heaving during the winter- spring period, and rill formation during the summer. We also found the evident seasonal changes in $$^{137}$$Cs concentration; high during the early spring and gradually decreased thereafter, then surface runoff from the plot frequently occurred during spring and autumn when rainfall was high and reached a maximum in summer.

論文

Dynamics of enhanced neoclassical particle transport of tracer impurity ions in ion temperature gradient driven turbulence

井戸村 泰宏; Obrejan, K.*; 朝比 祐一; 本多 充*

Physics of Plasmas, 28(1), p.012501_1 - 012501_11, 2021/01

 被引用回数:3 パーセンタイル:95.53(Physics, Fluids & Plasmas)

運動論的電子,バルクイオン,低Zおよび中Zのトレーサ不純物を含む大域的full-fジャイロ運動論シミュレーションを用いてイオン温度勾配駆動(ITG)乱流におけるトレーサ不純物輸送を調べた。この結果、乱流粒子輸送に加えて、乱流輸送と新古典輸送の相乗効果による拡張新古典輸送がトレーサ不純物輸送に大きく寄与することがわかった。ITGモードのバースト的励起が電子とバルクイオンの非両極性乱流粒子束を生成し、これが両極性条件に従う径電場の速い成長をもたらす。これに伴う$$Etimes B$$流の発散が磁気ドリフトによる輸送に関連する上下非対称な密度揺動を圧縮する。この密度揺動の振幅は$$Etimes B$$圧縮効果と磁力線方向運動による帰還電流の競合によって決まるため、拡張新古典輸送はイオン質量に依存する。この機構は温度には働かず、粒子輸送のみを選択的に増大する。

論文

Radionuclides from the Fukushima Daiichi Nuclear Power Plant in terrestrial systems

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

 被引用回数:17 パーセンタイル:81.26(Environmental Sciences)

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.

論文

Author correction; Radionuclides from the Fukushima Daiichi Nuclear Power Plant in terrestrial systems

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

 被引用回数:0 パーセンタイル:0.29(Environmental Sciences)

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.

論文

Dataset on the 6-year radiocesium transport in rivers near Fukushima Daiichi Nuclear Power Plant

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

 被引用回数:1 パーセンタイル:30.91(Multidisciplinary Sciences)

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.

論文

Land use types control solid wash-off rate and entrainment coefficient of Fukushima-derived $$^{137}$$Cs, and their time dependence

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

 被引用回数:9 パーセンタイル:62.46(Environmental Sciences)

This study provides the results of observations of plot-scale $$^{137}$$Cs wash-off from various land uses (two uncultivated farmlands, two cultivated farmlands, three grasslands and one forest) from 2011 to 2014. Annual $$^{137}$$Cs wash-off rate ranged from 0.0026 to 7.5% per year, and more vegetation cover resulted in lower sediment discharge. $$^{137}$$Cs concentration observed in uncultivated farmland plot decreased with time and the rate was lower than those of riverine, suggesting that contributions of $$^{137}$$Cs from the upslope area may be insignificant to that in riverine. A negative relationship between $$^{137}$$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 $$^{137}$$Cs concentration. A contribution of coarse organic matter to $$^{137}$$Cs wash-off was suggested in the forest, which had relatively high $$^{137}$$Cs concentration and low sediment discharge.

論文

Reconstruction of a Fukushima accident-derived radiocesium fallout map for environmental transfer studies

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

 被引用回数:14 パーセンタイル:73.59(Environmental Sciences)

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.

論文

Preface: Integration of knowledge on the radiological environment around the Fukushima Nuclear Power Plant site over a period of six years

斎藤 公明; 恩田 裕一*; 久松 俊一*

Journal of Environmental Radioactivity, 210, p.106003_1 - 106003_2, 2019/12

 被引用回数:2 パーセンタイル:58.2(Environmental Sciences)

福島第一原子力発電所事故から6年間の放射線環境の変化について記載した論文19編を集約した特集号の序文である。福島における状況の変化や知識集約の重要性、今後の課題等について簡潔にまとめている。

論文

Temporal change in radiological environments on land after the Fukushima Daiichi Nuclear Power Plant accident

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.

論文

Factors controlling dissolved $$^{137}$$Cs concentrations in east Japanese rivers

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

 被引用回数:8 パーセンタイル:62.46(Environmental Sciences)

福島第一原子力発電所事故の影響を受けた河川の溶存態放射性セシウム濃度の制御要因を明らかにするため、東日本66箇所の河川で調査を行った。溶存態$$^{137}$$Cs濃度について流域の平均$$^{137}$$Cs沈着量・土地利用・土壌組成・地形・水質との関連性を評価した結果、地形的な湿潤指標(TWI)が有意に正の相関を示した。ヨーロッパの河川でも同様の相関が認められるが、日本の河川では湿地帯ではなく市街地が溶存態$$^{137}$$Cs濃度に強く影響していた。

論文

Transport and redistribution of radiocesium in Fukushima fallout through rivers

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

 被引用回数:30 パーセンタイル:94.05(Engineering, Environmental)

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.

論文

Repeatability and reproducibility of measurements of low dissolved radiocesium concentrations in freshwater using different pre-concentration methods

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

 被引用回数:2 パーセンタイル:42.44(Chemistry, Analytical)

福島県の淡水に含まれる低レベル溶存態放射性セシウム濃度の測定に関する繰り返し精度と再現精度を評価した。21の実験施設が5つの異なる前濃縮法(プルシアンブルー含浸フィルターカートリッジ,リンモリブデン酸アンモニウム共沈,蒸発,固相抽出ディスク、およびイオン交換樹脂カラム)によって10L試料3検体を前濃縮し、放射性セシウム濃度を測定した。全$$^{137}$$Cs濃度測定結果のzスコアは$$pm$$2以内で、手法間の誤差は小さいことが示された。一方で、各実験施設内の相対標準偏差に比べて、施設間の相対標準偏差は大きかった。

論文

The Surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

北里 宏平*; Milliken, R. E.*; 岩田 隆浩*; 安部 正真*; 大竹 真紀子*; 松浦 周二*; 荒井 武彦*; 仲内 悠祐*; 中村 智樹*; 松岡 萌*; et al.

Science, 364(6437), p.272 - 275, 2019/04

 被引用回数:140 パーセンタイル:99.81(Multidisciplinary Sciences)

小惑星探査機はやぶさ2のターゲット天体であるリュウグウは、始原的な炭素質物質で構成されていると考えられている。はやぶさ2に搭載された近赤外分光計(NIRS3)によって、天体の表面組成を得た。天体全体の観測で、弱く細い吸収が2.72ミクロンに確認され、OHを含む鉱物の存在を示している。弱いOH吸収と低いアルベドは熱やショックによって変質を受けた炭素質コンドライトに似ている。OHバンドの位置はほとんど一定であり、衝撃片の集合によって形成されたリュウグウは組成的に均質であることを示している。

論文

Anisotropic magnetic fluctuations in ferromagnetic superconductor UGe$$_2$$; $$^{73}$$Ge-NQR study at ambient pressure

野間 雄一郎*; 小手川 恒*; 久保 徹郎*; 藤 秀樹*; 播磨 尚朝*; 芳賀 芳範; 山本 悦嗣; 大貫 惇睦*; 伊藤 公平*; Haller, E. E.*; et al.

Journal of the Physical Society of Japan, 87(3), p.033704_1 - 033704_5, 2018/03

 被引用回数:4 パーセンタイル:47.76(Physics, Multidisciplinary)

$$^{73}$$Ge nuclear quadrupole resonance study of ferromagnetic superconductor UGe$$_2$$ is reported. Detailed analyses successfully assigned crystallographic sites of Ge atoms. The measurement of the nuclear spin-lattice relaxation rate revealed highly anisotropic magnetic fluctuations.

論文

Effect of topsoil removal and selective countermeasures on radiocesium accumulation in rice plants in Fukushima paddy field

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

 被引用回数:1 パーセンタイル:5.42(Environmental Sciences)

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.

論文

台風201326号出水に伴う新田川起源懸濁態放射性核種の沿岸域でのインベントリ解析

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

福島新田川流域には原子力発電所事故直後に大量の放射性セシウム137($$^{137}$$Cs)が大気経由で沈着し、高濃度の懸濁態$$^{137}$$Csとして河道に集積したのち、出水毎に間欠的に海域へ供給され、沿岸域の底質環境に影響を与え続けている。本研究では、4段ネストJCOPE2-ROMS海洋モデル、波浪推算モデルSWAN、河川土砂流出モデルiRIC-Nays2DH、混合粒径土砂3次元海洋輸送モデル、放射性核種吸着モデルを連成させた超高解像度広域での土砂およびそれらに吸着した懸濁態$$^{137}$$Csの海洋移流分散モデリングを行い、台風201326号出水イベントに伴う新田川起源土砂の河口・沿岸域における輸送、再懸濁、堆積、浸食過程の時空間特性を評価した。その結果、台風通過直後に新田川から海域へ流入した懸濁態$$^{137}$$Csの総量の約45.3%は河口1km圏内に堆積していた。さらに、浅海域における沿岸漂砂の輸送には南方向への偏りがみられた。以上の結果は現地調査結果とも整合的であった。

論文

Time dependence of the $$^{137}$$Cs concentration in particles discharged from rice paddies to freshwater bodies after the Fukushima Daiichi NPP accident

吉村 和也; 恩田 裕一*; 若原 妙子*

Environmental Science & Technology, 50(8), p.4186 - 4193, 2016/04

 被引用回数:17 パーセンタイル:62.47(Engineering, Environmental)

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.

論文

Temporal changes of radiocesium in irrigated paddy fields and its accumulation in rice plants in Fukushima

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

 被引用回数:12 パーセンタイル:49.59(Environmental Sciences)

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.

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