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Misono, Toshiharu; Tsuruta, Tadahiko; Nakanishi, Takahiro; Sanada, Yukihisa
Global Environmental Research (Internet), 24(2), p.137 - 144, 2021/06
A large amount of radioactive material was released into the environment following the 2011 Great East Japan earthquake. Nine years have passed since this accident, and the radioactive concentration in the seabed sediments has decreased. However, the influence of rivers causes coastal areas to be dynamic. The Japan Atomic Energy Agency has conducted studies at the mouth of the Ukedo River. Here, we review previous studies and evaluate the radioactive Cs supplied by rivers using a sediment trap. In this study, a mooring system consisting of a sediment trap was installed in the Ukedo River estuary near the Fukushima Daiichi Nuclear Power Plant from February 2017 to November 2017. A calculation of the annual 
Cs flux estimated from the obtained contribution rates indicates that the contribution of resuspension to the flux was over 60% during this period. Therefore, this study shows that the mobilization of radioactive Cs in the coastal area is primarily due to resuspension.
Cs outflow from forest floor adjacent to a residential area; Comparison of decontaminated and non-decontaminated forest floorNiizato, Tadafumi; Watanabe, Takayoshi
Global Environmental Research (Internet), 24(2), p.129 - 136, 2021/06
The 3-years monitoring of Cs outflow associated with soil erosion in the decontaminated and no decontaminated sites using experimental plot was conducted in the forest of Fukushima during the rainy season. The Cs outflow in the decontaminated site was 10 to 14 times larger than that of no decontaminated site. However, the outflow in the decontaminated site decreased from 3.24% to 0.61% in corresponding with the recovery of the forest floor cover. When reaching of the forest floor cover to 60% and over, the Cs outflow in the decontaminated site turned into relatively minor fluctuations and similar level to the no decontaminated site. The decrease in the Cs outflow corresponding to the restoration of the forest floor cover was owing to the recovering of the protective effect of forest floor against the raindrop splash and decrease in ratio of the soil component with relatively high Cs activity in the particulate matter.
Cs in water and phyto- and zooplankton in a reservoir affected by the Fukushima Daiichi Nuclear Power Plant AccidentTsuji, 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 Cs and planktonic Cs were observed. Seasonal variations in dissolved 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 Cs concentrations and dominant species were found. The amount of planktonic form of Cs in the water was less than 1.4% of the total Cs in the lake water, therefore the effect of plankton on the dynamics of Cs in the lake was minimal.
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.
Kawase, Keiichi
Global Environmental Research (Internet), 20(1&2), p.83 - 90, 2017/03
Major challenges to implementing full-scale environmental decontamination were the absence of real-world examples and also lack of experience in planning and implementing decontamination technology appropriate to the physical and social boundary conditions in both Japan and Fukushima. The Japan Atomic Energy Agency was thus charged with conducting a range of Decontamination Pilot Project to examine the applicability of decontamination technologies, with a special focus on reducing dose rates and thus allowing evacuees to return to re-establish their normal lifestyles as quickly as possible, whilst simultaneously maintaining worker safety. In this report, re-edit the report of the Decontamination Pilot Project (Nakayama et al.,2014), do the commentary for the decontamination technology.
Ohara, Toshimasa*; Miyahara, Kaname
Global Environmental Research (Internet), 20(1&2), p.3 - 13, 2017/03
Toward the environmental regeneration in Fukushima Prefecture and other areas after the Fukushima Daiichi Nuclear Power Station accidents, JAEA and NIES working with many public and private sector organizations and academia have carried out multifaceted research that will help to restore the environment of affected areas. These challenging efforts need to be further strengthened.
Kawamura, Hideyuki; Kobayashi, Takuya; Nishikawa, Shiro*; Ishikawa, Yoichi*; Usui, Norihisa*; Kamachi, Masafumi*; Aso, Noriko*; Tanaka, Yusuke*; Awaji, Toshiyuki*
Global Environmental Research (Internet), 18(1), p.81 - 96, 2014/09
A drift simulation of tsunami debris flushed out from the Tohoku district, Japan, into the North Pacific due to the tsunami on March 11, 2011, has been conducted to monitor and forecast the drift path over the North Pacific. Results showed that tsunami debris was first transported eastward by the intense Kuroshio Extension and westerly, spreading in the north and south directions by both an energetic ocean eddy and a storm track over the ocean. Tsunami debris with larger windage was transported over the North Pacific by ocean surface wind rather than ocean current and arrived at the west coast of the North American Continent in the fall of 2011. Tsunami debris located near the North American Continent migrated, associated with the basin-scale seasonal change in the atmospheric pressure pattern. Our forecast run suggested that the tsunami debris belt will be formed from the North American Continent in the east to the Philippines in the west.
