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Journal Articles

Impact of fluvial discharge on $$^{137}$$Cs in the ocean following the Fukushima Daiichi Nuclear Power Station accident

Tsumune, Daisuke*; Tsubono, Takaki*; Misumi, Kazuhiro*; Sakuma, Kazuyuki; Onda, Yuichi*

Pure and Applied Chemistry, 16 Pages, 2024/00

Twelve years after the Fukushima Daiichi Nuclear Power Station (F1NPS) accident, $$^{137}$$Cs activity concentrations have not yet decreased to pre-accident levels because of direct release from the site and fluvial discharges of $$^{137}$$Cs deposited on land. It is necessary to consider dispersion processes in the coastal area to understand the impact of multiple river discharges and direct release. To achieve this goal, we carried out oceanic dispersion simulations that considered direct release and fluvial discharges and compared the results with the annual averages of observed data. We assumed that particulate $$^{137}$$Cs discharged from rivers to the ocean quickly resuspended and re-leached after coagulation and precipitation and that all of the $$^{137}$$Cs were dispersed. The reproducibility of results was improved by considering fluvial discharges of particulate $$^{137}$$Cs at all sites between 2013 and 2016, except near the F1NPS. In other words, particulate $$^{137}$$Cs discharged from rivers was found to influence the results of ocean surface activity concentrations within a relatively short period of time. The impact of direct release was dominant for the observed $$^{137}$$Cs activity concentrations adjacent to the F1NPS, which was used to estimate direct releases.

Journal Articles

Temporal variability of $$^{137}$$Cs concentrations in coastal sediments off Fukushima

Suzuki, Shotaro*; Amano, Yosuke*; Enomoto, Masahiro*; Matsumoto, Akira*; Morioka, Yoshiaki*; Sakuma, Kazuyuki; Tsuruta, Tadahiko; Kaeriyama, Hideki*; Miura, Hikaru*; Tsumune, Daisuke*; et al.

Science of the Total Environment, 831, p.154670_1 - 154670_15, 2022/07

 Times Cited Count:2 Percentile:32.35(Environmental Sciences)

Journal Articles

A Storm-induced flood and associated nearshore dispersal of the river-derived suspended $$^{137}$$Cs

Uchiyama, Yusuke*; Tokunaga, Natsuki*; Azuma, Kohei*; Kamidaira, Yuki; Tsumune, Daisuke*; Iwasaki, Toshiki*; Yamada, Masatoshi*; Tateda, Yutaka*; Ishimaru, Takashi*; Ito, Yukari*; et al.

Science of the Total Environment, 816, p.151573_1 - 151573_13, 2022/04

 Times Cited Count:5 Percentile:71.31(Environmental Sciences)

no abstracts in English

Journal Articles

First isolation and analysis of caesium-bearing microparticles from marine samples in the Pacific coastal area near Fukushima Prefecture

Miura, Hikaru*; Ishimaru, Takashi*; Ito, Yukari*; Kuribara, Yuichi; Otosaka, Shigeyoshi*; Sakaguchi, Aya*; Misumi, Kazuhiro*; Tsumune, Daisuke*; Kubo, Atsushi*; Higaki, Shogo*; et al.

Scientific Reports (Internet), 11, p.5664_1 - 5664_11, 2021/03

 Times Cited Count:10 Percentile:68.7(Multidisciplinary Sciences)

For the first time, we isolated and investigated seven CsMPs (radioactive caesium-bearing microparticles) from marine particulate matter and sediment. From the elemental composition, the $$^{134}$$Cs/$$^{137}$$Cs activity ratio, and the $$^{137}$$Cs activity per unit volume results, we inferred that the five CsMPs collected from particulate matter were emitted from Unit 2 of the FDNPP, whereas the two CsMPs collected from marine sediment were possibly emitted from Unit 3. The presence of CsMPs can cause overestimation of the solid-water distribution coefficient of Cs in marine sediments and particulate matter and a high apparent radiocaesium concentration factor for marine biota. CsMPs emitted from Unit 2, which were collected from the estuary of a river that flowed through a highly contaminated area, may have been deposited on land and then transported by the river. By contrast, CsMPs emitted from Unit 3 were possibly transported eastward by the wind and deposited directly onto the ocean surface.

Journal Articles

Characterization of two types of cesium-bearing microparticles emitted from the Fukushima accident via multiple synchrotron radiation analyses

Miura, Hikaru*; Kuribara, Yuichi; Yamamoto, Masayoshi*; Sakaguchi, Aya*; Yamaguchi, Noriko*; Sekizawa, Oki*; Nitta, Kiyofumi*; Higaki, Shogo*; Tsumune, Daisuke*; Itai, Takaaki*; et al.

Scientific Reports (Internet), 10, p.11421_1 - 11421_9, 2020/07

 Times Cited Count:18 Percentile:69.84(Multidisciplinary Sciences)

Journal Articles

Inventory analysis of suspended radiocesium derived from Niida River during a typhoon-induced flood event

Uchiyama, Yusuke*; Azuma, Kohei*; Odani, Sachika*; Iwasaki, Toshiki*; Tsumune, Daisuke*; Kamidaira, Yuki; Shimizu, Yasuyuki*; Onda, Yuichi*

Doboku Gakkai Rombunshu, B2 (Kaigan Kogaku) (Internet), 73(2), p.I_685 - I_690, 2017/10

no abstracts in English

Journal Articles

Factors controlling the spatiotemporal variation of $$^{137}$$Cs in seabed sediment off the Fukushima coast; Implications from numerical simulations

Misumi, Kazuhiro*; Tsumune, Daisuke*; Tsubono, Takaki*; Tateda, Yutaka*; Aoyama, Michio*; Kobayashi, Takuya; Hirose, Katsumi*

Journal of Environmental Radioactivity, 136, p.218 - 228, 2014/10

 Times Cited Count:22 Percentile:54.4(Environmental Sciences)

Major controls on spatiotemporal variations of $$^{137}$$Cs activity in seabed sediments derived from the Fukushima Dai-ichi Nuclear Power Plant accident during the first year after the accident were investigated by using numerical simulations. The model successfully reproduced major features of the observed spatiotemporal variations of $$^{137}$$Cs activity in sediments. The spatial pattern of $$^{137}$$Cs in sediments, which mainly reflected the history of $$^{137}$$Cs activity in the bottom water overlying the sediment and the sediment particle size distribution, became established during the first several months after the accident. Taking $$^{137}$$Cs activities in sediments in the coastal area and in the vicinity of the power plant into account, increased the simulated total inventory of $$^{137}$$Cs in sediments off the Fukushima coast to a value on the order of 10$$^{14}$$ Bq.

Journal Articles

Oceanic dispersion simulations of $$^{137}$$Cs released from the Fukushima Daiichi Nuclear Power Plant

Masumoto, Yukio*; Miyazawa, Yasumasa*; Tsumune, Daisuke*; Tsubono, Takaki*; Kobayashi, Takuya; Kawamura, Hideyuki; Estournel, C.*; Marsaleix, P.*; Lanerolle, L.*; Mehra, A.*; et al.

Elements, 8(3), p.207 - 212, 2012/06

 Times Cited Count:79 Percentile:92.15(Geochemistry & Geophysics)

Present status of oceanic dispersion simulations of cesium 137 ($$^{137}$$Cs) directly discharged from Fukushima Daiichi Nuclear Power Plant are reviewed using five model outputs and other available informations, focusing on estimations of discharged amount of $$^{137}$$Cs and subsequent dispersion in a region off Fukushima during March and April, 2011. Common aspects and discrepancies among the simulated results are described. While the discharged amount spreads from about 1 to 27 P Bq of $$^{137}$$Cs among the estimates, the values obtained from the five models indicate 2 to 4 P Bq. With these total amounts and time evolutions of the discharge rate, mimicking observed $$^{137}$$Cs concentration near FDNPP, as a source for the dispersion calculation, all the five models simulated the $$^{137}$$Cs dispersion in the ocean reasonably well corresponding to the observed distributions.

Oral presentation

Dynamics of radionuclides and ecosystem response in the coastal area of Fukushima KS-21-23, KS-22-14

Takata, Hyoe*; Otsuki, Azusa*; Sato, Shun*; Otosaka, Shigeyoshi*; Toda, Ryoji*; Nishikawa, Jun*; Kenmochi, Hideyuki*; Ishikura, Mei*; Yamada, Momoka*; Shinkai, Yusuke*; et al.

no journal, , 

Research cruises were conducted by the Shinsei Maru from October 7 to October 17, 2021, and from October 2 to 13, 2022, in the coastal waters off Fukushima Prefecture. Those cruises aimed to monitor radionuclide distribution and to clarify the dynamics of radionuclides in the coastal water and the environmental response of ecosystems after the Fukushima Daiichi Nuclear Power Plant accident in March 2011.

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