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Otosaka, Shigeyoshi*; Kambayashi, Shota*; Fukuda, Miho*; Tsuruta, Tadahiko; Misono, Toshiharu; Suzuki, Takashi; Aono, Tatsuo*
Environmental Science & Technology, 54(21), p.13778 - 13785, 2020/11
Times Cited Count：15 Percentile：54.61(Engineering, Environmental)Concentrations of 
Cs in seawater, seabed sediment, and pore water collected from the area around Fukushima were investigated from 2015 to 2018, and the potential of coastal sediments to supply radiocesium to the bottom environment was evaluated. The Cs concentration in the pore water ranged from 33 to 1934 mBq L
and was 10-40 times higher than that in the overlying water (seawater overlying within 30 cm on the seabed). At most stations, the Cs concentrations in the overlying water and the pore water were approximately proportional to those in the sediment. The conditional partition coefficient between pore water and sediment was 0.9-14
10
L kg, independent of the year of sampling. These results indicated that an equilibrium of Cs between pore water and sediment has established in a relatively short period, and Cs in the pore water is gradually exported to seawater near the seabed. A simple box model estimation based on these results showed that the Cs in the sediment was decreased by about 6% per year by desorption/diffusion of Cs from the seabed.
Otosaka, Shigeyoshi*; Aono, Tatsuo*; Fukuda, Miho*; Kambayashi, Shota*; Misono, Toshiharu; Dohi, Terumi; Tsuruta, Tadahiko; Suzuki, Takashi; Takahashi, Yoshio*; Sugihara, Naoko*; et al.
no journal, ,
While the amount of cesium-137 (Cs: half-life 30.1 years) accumulated on the seabed due to the accident of the Fukushima Daiichi Nuclear Power Plant (0.1-0.2 PBq) is only about 1 to 2% of the total amount of Cs transported to the ocean, it has been reported that it will remain for a long time in the coastal areas. On the other hand, long-term migration process of the sedimentary radiocesium and the impact on the ecosystem near the seafloor remain unknown. In this presentation, we will give an overview of the distribution and behavior of Cs, especially on the seafloor along the coast of Fukushima, and report the latest results on the processes I the seafloor that should be considered on decadal timescale.
Aono, Tatsuo*; Nishikawa, Jun*; Otosaka, Shigeyoshi*; Takata, Hyoe*; Misono, Toshiharu; Nakanishi, Takahiro; Miura, Hikaru*; Kambayashi, Shota*; Fukuda, Miho*; Sakurada, Masanobu*; et al.
no journal, ,
From 2016 to 2020, the Tohoku Marine Ecosystem Research Vessel Shinsei-maru conducted four research cruises on the dynamics and bioavailability of radionuclides around off Fukushima. Seawater, sediments and organisms were collected mainly around off the Fukushima Daiichi Nuclear Power Plant (FDNPS). The purpose of those cruises is to observe the flux of radionuclides released into the ocean by the FDNPS accident and to understand the bioavailability of radionuclides. In order to understand the contaminated levels of the marine environment, the concentration of radioactive cesium (Cs) in seawater and sediments around off Fukushima was investigated. As a result, the concentration range of dissolved Cs-137 in the surface seawater near the FDNPS from 2016 to 2018 was 10-23 mBq/L, but decreased to 7 mBq/L in 2020. In terms of points, the concentrations of dissolved Cs-137 tended to decrease with time. On the other hand, in sediments, the Cs-137 concentrations were higher in the surface layer (0-2 cm) than the deep layer from 2016 to 2017 and tended to decrease with depth, but after 2018, subsurface vertical maximum of Cs-137 concentrations was observed at some stations. Although these concentrations tended to increase in the subsurface layer, the concentrations in the sediment also tended to decrease with time. In this presentation, we report on the concentration variation of Cs-137 and their characteristics in seawater and sediments around off Fukushima.
Aono, Tatsuo*; Fukuda, Miho*; Sakurada, Masanobu*; Takahashi, Hiroyuki*; Yamazaki, Shinnosuke*; Kambayashi, Shota*; Misono, Toshiharu; Nakanishi, Takahiro; Miura, Hikaru*; Nishikawa, Jun*; et al.
no journal, ,
From 2016 to 2020, R/V Shinsei-maru of JAMSTEC conducted four research cruises on the dynamics and bioavailability of radionuclides around off Fukushima. Seawater, sediments and organisms were collected mainly around off the Fukushima Daiichi Nuclear Power Plant (FDNPS). The purpose of those cruises is to observe the flux of radionuclides released into the ocean by the FDNPS accident and to understand the bioavailability of radionuclides. In order to understand the contaminated levels of the marine environment, the concentration of radiocaesium (Cs) in seawater and sediments around off Fukushima was investigated.
Aono, Tatsuo*; Nishikawa, Jun*; Otosaka, Shigeyoshi*; Takata, Hyoe*; Misono, Toshiharu; Nakanishi, Takahiro; Miura, Hikaru*; Fukuda, Miho*; Kambayashi, Shota*; Sakurada, Masanobu*; et al.
no journal, ,
From 2016 to 2020, four research voyages were conducted to investigate the dynamics of radioactive materials in the waters around Fukushima. Seawater and sediment samples were collected in the waters off the Fukushima Daiichi Nuclear Power Plant (FDNPS). The concentration of radioactive cesium (Cs) in seawater and sediment off the coast of Fukushima was surveyed to understand the status of the marine environment. As a result, no significant changes were observed in both seawater and sediment from 2016 to 2020.
