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論文

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

鈴木 翔太郎*; 天野 洋典*; 榎本 昌宏*; 松本 陽*; 守岡 良晃*; 佐久間 一幸; 鶴田 忠彦; 帰山 秀樹*; 三浦 輝*; 津旨 大輔*; et al.

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

The monthly monitoring data (total 3647 samples) between May. 2011 and Mar. 2020 were analyzed to describe temporal variability of $$^{137}$$Cs concentration in coastal sediments off Fukushima. $$^{137}$$Cs concentration of sediment had decreasing trend, but non-linear model fitting suggested that this decreasing trend showed slower. Additionally, $$^{137}$$Cs concentration were up to 4.08 times greater in shallow sampling sites (7, 10, 20 m depth) following heavy rainfall events (before five months vs. after five months), such as typhoons. These were consistent with increasing particulate $$^{137}$$Cs (P-$$^{137}$$Cs) fluxes from river and increasing dissolved $$^{137}$$Cs (D-$$^{137}$$Cs) concentration in seawater. Finally, the numerical experiment was conducted and revealed that riverine $$^{137}$$Cs input could preserve $$^{137}$$Cs concentration in coastal sediment. These results indicate that riverine $$^{137}$$Cs input via heavy rainfall events is one of the main factors for preserving $$^{137}$$Cs concentration in coastal sediment off Fukushima.

口頭

Contribution of particulate $$^{137}$$Cs from rivers to $$^{137}$$Cs concentrations in coastal sediment off Fukushima

鈴木 翔太郎*; 佐久間 一幸; 鶴田 忠彦; 松本 陽*; 天野 洋典*; 榎本 昌宏*; 守岡 良晃*; 神山 享一*; 高田 兵衛*

no journal, , 

To evaluate contribution of riverine particulate $$^{137}$$Cs input, we estimated $$^{137}$$Cs concentration coastal sediment (7-20 m depth) with particulate $$^{137}$$Cs flux of the total 13 rivers (Uda, Mano, Niida, Ohta, Odaka, Ukedo(+Takase), Maeda, Kuma, Tomioka, Ide, Kido, Natsui, Same) calculated by tank model for water discharge and empirical equations for suspended solids fluxes and $$^{137}$$Cs discharge between May 2011 and March 2020. Calculated particulate $$^{137}$$Cs flux from the river were ranged from 2.11$${times}$$10$$^{9}$$ to 4979$${times}$$10$$^{9}$$ Bq/month. Estimated $$^{137}$$Cs concentration including particulate $$^{137}$$Cs via deposition kept concentration level more than minimum 0.351 Bq/kg-dry when initial $$^{137}$$Cs concentration, variation rate and deposition ratio were set 300 Bq/kg-dry, -95% and 0.1, respectively.

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