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Journal Articles

Ten years of warming increased plant-derived carbon accumulation in an East Asian monsoon forest

Zhang, J.*; Kuang, L.*; Mou, Z.*; Kondo, Toshiaki*; Koarashi, Jun; Atarashi-Andoh, Mariko; Li, Y.*; Tang, X.*; Wang, Y.-P.*; Pe$~n$uelas, J.*; et al.

Plant and Soil, 481(1-2), p.349 - 365, 2022/12

 Times Cited Count:0 Percentile:24.8(Agronomy)

Journal Articles

Radiocesium-bearing microparticles cause a large variation in $$^{137}$$Cs activity concentration in the aquatic insect ${it Stenopsyche marmorata}$ (Tricoptera: Stenopsychidae) in the Ota River, Fukushima, Japan

Ishii, Yumiko*; Miura, Hikaru*; Jo, J.*; Tsuji, Hideki*; Saito, Rie; Koarai, Kazuma; Hagiwara, Hiroki; Urushidate, Tadayuki*; Nishikiori, Tatsuhiro*; Wada, Toshihiro*; et al.

PLOS ONE (Internet), 17(5), p.e0268629_1 - e0268629_17, 2022/05

 Times Cited Count:3 Percentile:45.99

We investigated the variability in $$^{137}$$Cs activity concentration in individual aquatic insects in detritivorous caddisfly (${it Stenopsyche marmorata}$) and carnivorous dobsonfly (${it Protohermes grandis}$) larvae from the Ota River, Fukushima. Caddisfly larvae showed sporadically higher radioactivity, whereas no such outliers were observed in dobsonfly larvae. Autoradiography and scanning electron microscopy analyses confirmed that these caddisfly larvae samples contained radiocesium-bearing microparticles (CsMPs), which are insoluble Cs-bearing silicate glass particles. CsMPs were also found in potential food sources of caddisfly larvae, such as periphyton and drifting particulate organic matter, indicating that larvae may ingest CsMPs along with food particles of similar size. Although CsMPs distribution and uptake by organisms in freshwater ecosystems is relatively unknown, our study demonstrates that CsMPs can be taken up by aquatic insects.

Journal Articles

Remobilisation of radiocaesium from bottom sediments to water column in reservoirs in Fukushima, Japan

Funaki, Hironori; Tsuji, Hideki*; Nakanishi, Takahiro; Yoshimura, Kazuya; Sakuma, Kazuyuki; Hayashi, Seiji*

Science of the Total Environment, 812, p.152534_1 - 152534_10, 2022/03

 Times Cited Count:8 Percentile:58.13(Environmental Sciences)

Reservoir sediments generally act as a sink for radionuclides derived from nuclear accidents, but under anaerobic conditions, several radionuclides remobilise in bioavailable form from sediment to water columns, which may contribute to a long-term contamination in aquatic products. This study systematically investigated the $$^{137}$$Cs activities between sediment and pore water, which is a direct evidence of the remobilisation of bioavailable $$^{137}$$Cs from sediments, in two highly contaminated reservoirs affected by the Fukushima Dai-ichi Nuclear Power Plant accident. Our results strongly indicate a competitive ion exchange process between $$^{137}$$Cs and NH$$_{4}$$ via a highly selective interaction with the frayed edges sites of phyllosilicate minerals to be the major reason for the variability of the Kd values between sediment and pore water, even in the Fukushima case.

Journal Articles

General overview of the research project investigating the radionuclide solution behavior in mock mortar matrix modeled after conditions at the Fukushima-Daiichi Nuclear Power Station

Igarashi, Go*; Haga, Kazuko*; Yamada, Kazuo*; Aihara, Haruka; Shibata, Atsuhiro; Koma, Yoshikazu; Maruyama, Ippei*

Journal of Advanced Concrete Technology, 19(9), p.950 - 976, 2021/09

 Times Cited Count:5 Percentile:41.06(Construction & Building Technology)

Journal Articles

Dynamics of $$^{137}$$Cs in water and phyto- and zooplankton in a reservoir affected by the Fukushima Daiichi Nuclear Power Plant Accident

Tsuji, Hideki*; Nakagawa, Megumi*; Iijima, Kazuki; Funaki, Hironori; Yoshimura, Kazuya; Sakuma, Kazuyuki; Hayashi, Seiji*

Global Environmental Research (Internet), 24(2), p.115 - 127, 2021/06

Lake water, phytoplankton and zooplankton were sampled by a total of 12 quarterly surveys from August 2014 to May 2017 at a dam lake in the Fukushima nuclear disaster area, and variations of dissolved form of $$^{137}$$Cs and planktonic $$^{137}$$Cs were observed. Seasonal variations in dissolved $$^{137}$$Cs concentration with high in summer and low in winter were observed in the upstream, midstream and downstream areas of the lake, but no seasonal or site specific differences in planktonic $$^{137}$$Cs concentrations and dominant species were found. The amount of planktonic form of $$^{137}$$Cs in the water was less than 1.4% of the total $$^{137}$$Cs in the lake water, therefore the effect of plankton on the dynamics of $$^{137}$$Cs in the lake was minimal.

Journal Articles

Overview of environmental impact assessment studies on radioactive contamination after the Fukushima Daiichi Nuclear Power Plant accident

Iijima, Kazuki; Hayashi, Seiji*; Tamaoki, Masanori*

Global Environmental Research (Internet), 24(2), p.85 - 93, 2021/06

Environmental radioactive contamination by the Fukushima Daiichi Nuclear Power Plant accident has clearly been declining during the passage of almost 10 years from the accident. However, the prolongation of radioactive contamination in natural ecosystems probably derived from forested area without decontamination is pointed out by many studies, so more detailed examination will be needed for environmental dynamics of bioavailable radiocesium and its transfer to ecosystems. Also for influence of radiation to organisms, effects of evacuation on wild organisms are more pronounced than direct effect from radiation, especially in Fukushima evacuation area.

Journal Articles

A Project focusing on the contamination mechanism of concrete after the accident at Fukushima Daiichi Nuclear Power Plant

Yamada, Kazuo*; Maruyama, Ippei*; Haga, Kazuko*; Igarashi, Go*; Aihara, Haruka; Tomita, Sayuri*; Kiran, R.*; Osawa, Norihisa*; Shibata, Atsuhiro; Shibuya, Kazutoshi*; et al.

Proceedings of International Waste Management Symposia 2021 (WM2021) (CD-ROM), 10 Pages, 2021/03

Journal Articles

Evaluation of bioavailable radiocesium in the sediment in forest river and dam reservoir

Takechi, Seiichi*; Tsuji, Hideki*; Koshikawa, Masami*; Ito, Shoko*; Funaki, Hironori; Hayashi, Seiji*

Rikusuigaku Zasshi, 82(1), p.1 - 16, 2021/02

Since the Fukushima Daiichi Nuclear Power Plant accident in 2011, soil minerals and organic matter including radiocesium have been deposited in the dam lakes near the nuclear power plant. There is concern that radiocesium will gradually leach from the lake bottom into the lake water, resulting in prolonged radioactive contamination of the freshwater ecosystems especially in downstream of the dams. In this study, we collected undisturbed sediment core samples at the center of the Yokokawa Dam lake in Fukushima Prefecture and suspended sediment in the inflowing river of the dam for 4 years and evaluated the amount of bioavailable form of radiocesium (exchanged, oxidized, and organic forms) in these samples by sequential extraction tests using the BCR method focusing on the temporal change.

Journal Articles

New project on the analysis of contamination mechanisms of concrete at the Fukushima Daiichi Nuclear Power Station

Yamada, Kazuo*; Maruyama, Ippei*; Koma, Yoshikazu; Haga, Kazuko*; Igarashi, Go*; Shibuya, Kazutoshi*; Aihara, Haruka

Proceedings of International Waste Management Symposia 2019 (WM2019) (CD-ROM), 6 Pages, 2019/03

Journal Articles

Concentration of iodine-129 in surface seawater at subarctic and subtropical circulations in the Japan Sea

Suzuki, Takashi; Otosaka, Shigeyoshi; Togawa, Orihiko

Nuclear Instruments and Methods in Physics Research B, 294, p.563 - 567, 2013/01

 Times Cited Count:5 Percentile:38.75(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Surface concentrations of $$^{129}$$I around the subarctic front in the Japan Sea

Suzuki, Takashi; Otosaka, Shigeyoshi; Togawa, Orihiko

Dai-13-Kai AMS Shimpojiumu Hokokusho, p.69 - 72, 2011/01

no abstracts in English

Journal Articles

Iron distributions in the water column of the Japan Basin and Yamato Basin (Japan Sea)

Fujita, Satoshi*; Kuma, Kenshi*; Ishikawa, Satoko*; Nishimura, Shotaro*; Nakayama, Yuta*; Ushizaka, Satomi*; Isoda, Yutaka*; Otosaka, Shigeyoshi; Aramaki, Takafumi*

Journal of Geophysical Research, 115(C12), p.C12001_1 - C12001_12, 2010/12

 Times Cited Count:14 Percentile:38.73(Oceanography)

Vertical distributions of dissolved iron (D-Fe, less than 0.22 micrometer fraction), total iron (T-Fe, unfiltered), and chemical and biological components (e.g., nutrients) in seawater were determined at seven stations in the Japan Sea to understand the mechanisms that control iron behavior. Distributions of the D-Fe were characterized by surface depletion, mid-depth maxima, then slight decrease with depth in deep water and uniform concentration in bottom water because of biological uptake in the surface water and release from microbial decomposition of sinking organic matter in mid-depth water. The T-Fe concentrations in the deep-water column were variable with different T-Fe levels among stations and depths. We found a significant relationship of the exponential increase in the T-Fe concentrations with decreasing water transmittance, resulting from the iron supply into the deep and bottom waters due to the lateral transport of resuspended sediment from the continental slope.

Journal Articles

Spatial distribution of $$Delta$$$$^{14}$$C values of organic matter in surface sediments off Saru River in northern Japan, one year after a flood event in 2006

Nagao, Seiya*; Irino, Tomohisa*; Aramaki, Takafumi*; Ikehara, Ken*; Katayama, Hajime*; Otosaka, Shigeyoshi; Uchida, Masao*; Shibata, Yasuyuki*

Radiocarbon, 52(3), p.1068 - 1077, 2010/08

 Times Cited Count:0 Percentile:0.01(Geochemistry & Geophysics)

This study discusses the effects of flooding on the spatial distribution of organic matter on the shelf region of off the Saru River, southern part of Hokkaido, Japan, on the basis of the $$Delta$$$$^{14}$$C and $$delta$$$$^{13}$$C values. Surface sediments on the shelf were collected in August 2007, one year after the severe flood in 2006. Suspended particles and sediment of the Saru River were also collected in August 2007 and 2008. The $$Delta$$$$^{14}$$C values of organic matter in the shelf sediments ranged from -665 to -77 per mil. The silt and clay sediments had $$Delta$$$$^{14}$$C values of -240 to -77 per mil, but the sandy sediments ranged from -665 to -388 per mil. The $$Delta$$ values of particulate organic carbon in the Saru River are -292 to -247 per mil at normal flow conditions. These results indicate that surface soil with relatively older organic matter is deposited on the shelf region by the flooding event, and freshly-produced organic matter in sea surface is deposited after the flooding.

Journal Articles

Radiocarbon in the Japan Sea during the last 10 years

Aramaki, Takafumi*; Togawa, Orihiko; Otosaka, Shigeyoshi

JAEA-Conf 2010-001, p.39 - 43, 2010/03

no abstracts in English

Journal Articles

Distribution and transport process of radiocarbon in the Japan Sea

Otosaka, Shigeyoshi; Suzuki, Takashi; Tanaka, Takayuki

KURRI-KR-153, p.41 - 46, 2010/03

It is considered that recent distribution of anthropogenic radionuclides in the Japan Sea was controlled by supply of the radionuclides due to the global fallout and seawater circulation of the interior of the sea, rather than by a specific nuclear facility/incident. The detailed transport processes, however, have not been elucidated at the present. In this study, the authors surveyed distribution of radiocarbon at 81 stations in the Japan Sea and traced the fate of anthropogenic radiocarbon. As a result, principal transport process of radiocarbon, such as (1) supply from the East China Sea, (2) northward transport at the surface according to the Tsushima Warm Current, and (3) vertical transport in the northwestern region, were confirmed. In addition, the amount of anthropogenic radiocarbon in the sea was estimated by using a simple box-model.

JAEA Reports

Establishment of database for Japan Sea parameters on marine environment and radioactivity (JASPER), 2; Radiocarbon and oceanographic properties

Otosaka, Shigeyoshi; Suzuki, Takashi; Tanaka, Takayuki; Ito, Toshimichi; Kobayashi, Takuya; Kawamura, Hideyuki; Minakawa, Masayuki*; Aramaki, Takafumi*; Senju, Tomoharu*; Togawa, Orihiko

JAEA-Data/Code 2009-020, 27 Pages, 2010/02

JAEA-Data-Code-2009-020.pdf:2.45MB

The database for the Japan Sea parameters on marine environment and radionuclides (JASPER) has been established by the Japan Atomic Energy Agency as a product of the Japan Sea Expeditions. By the previous version of the database, data for representative anthropogenic radionuclides were opened to public. And now, data for radiocarbon and fundamental oceanographic properties (salinity, temperature, dissolved oxygen) including nutrients (silicate, phosphate, nitrate and nitrite) are released as the second volume of the database. In the second volume, 20,398 data records are stored including 2,695 data for temperature, 2,883 data for salinity, 2,109 data for dissolved oxygen, 11,051 data for the nutrients, and 1,660 data for radiocarbon. The database will be a strong tool for the continuous monitoring for contamination by anthropogenic radionuclides, studies on biogeochemical cycle, and development and validation of models for numerical simulations in the sea.

Journal Articles

Temporal and spatial variations of radiocarbon in Japan Sea Bottom Water

Kumamoto, Yuichiro*; Aramaki, Takafumi*; Watanabe, Shuichi*; Yoneda, Minoru*; Shibata, Yasuyuki*; Togawa, Orihiko; Morita, Masatoshi*; Shitashima, Kiminori*

Journal of Oceanography, 64(3), p.429 - 441, 2008/06

 Times Cited Count:11 Percentile:25.57(Oceanography)

In 1995 and 2000, radiocarbon ratio ($$Delta$$$$^{14}$$C) of total dissolved inorganic carbon was measured in the Japan Sea, a semi-closed marginal sea in the western North Pacific, where deep and bottom waters are formed in itself. Compiling them with historical radiocarbon data in the Japan Sea, temporal and spatial variations of the radiocarbon in the bottom water below 2000 m depth were elucidated. $$Delta$$$$^{14}$$C in the bottom waters in the western Japan and Yamato Basins increased by about 20 ‰ between 1977/79 and 1995 and did not changed between 1995 and 1999/2000, suggesting penetration of surface bomb-produced radiocarbon into the bottom waters due to bottom ventilation in the earlier period and stagnation of the bottom ventilation in the following period, respectively. In the eastern Japan Basin, the bottom $$Delta$$$$^{14}$$C increased by about 10 ‰ between 1977/79 and 2002, suggesting less ventilation of the bottom water in the basin. The temporal changes of the radiocarbon, tritium, and dissolved oxygen suggest sporadic occurrences of the bottom ventilation between 1979 and 1984 and its stagnation between 1984 and 2004 in the eastern Japan and Yamato Basins. The former is probably due to spreading of a newly ventilated bottom water in the western Japan Basin in the severe winter of 1976-1977 along the abyssal circulation in the Japan Sea. The latter does not conflict with temporal changes of bomb-produced $$^{137}$$Cs and chlorofluorocarbon-11 in the bottom water.

Journal Articles

Seawater movement in the Japan Sea inferred from $$^{14}$$C measurement in seawater

Otosaka, Shigeyoshi; Tanaka, Takayuki; Togawa, Orihiko; Amano, Hikaru; Aramaki, Takafumi*

JAEA-Conf 2008-003, p.63 - 66, 2008/04

Research Group for Environmental Science, JAEA has been carried out oceanographic observations in the Japan Sea. More than 3000 seawater samples for measurement of radiocarbon were collected during the observations. Radiocarbon in seawater samples was measured at AMS facility in JAEA Mutsu. In this presentation, circulation of water mass in the northern Japan Sea inferred from the radiocarbon measurement is discussed.

Journal Articles

Distribution of radiocarbon and bottom water circulation in the Japan Sea

Aramaki, Takafumi*; Togawa, Orihiko; Otosaka, Shigeyoshi; Suzuki, Takashi; Amano, Hikaru; Tanaka, Takayuki; Senju, Tomoharu*; Minakawa, Masayuki*

JAEA-Conf 2008-005, p.149 - 152, 2008/03

no abstracts in English

Journal Articles

Circulation in the northern Japan Sea studied chiefly with radiocarbon

Aramaki, Takafumi*; Senju, Tomoharu*; Togawa, Orihiko; Otosaka, Shigeyoshi; Suzuki, Takashi; Kitamura, Toshikatsu; Amano, Hikaru; Volkov, Y. N.*

Radiocarbon, 49(2), p.915 - 924, 2007/10

 Times Cited Count:8 Percentile:24.1(Geochemistry & Geophysics)

no abstracts in English

68 (Records 1-20 displayed on this page)