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Exchange of radiocesium between sediment and pore water in the coast off Fukushima(福島周辺海域における堆積物ー間隙水の放射性セシウムの交換 )
https://repo.qst.go.jp/records/67035
https://repo.qst.go.jp/records/670351321cede-f60c-453a-af27-91a9807e557f
| Item type | 会議発表用資料 / Presentation(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2018-12-18 | |||||
| タイトル | ||||||
| タイトル | Exchange of radiocesium between sediment and pore water in the coast off Fukushima(福島周辺海域における堆積物ー間隙水の放射性セシウムの交換 ) | |||||
| 言語 | ||||||
| 言語 | jpn | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_c94f | |||||
| 資源タイプ | conference object | |||||
| アクセス権 | ||||||
| アクセス権 | metadata only access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_14cb | |||||
| 著者 |
乙坂重嘉
× 乙坂重嘉× 福田, 美保× 青野, 辰雄× 福田 美保× 青野 辰雄 |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | In the coastal region of Fukushima, 137Cs concentration which is higher than before the accident is detected from the seabed even though the concentration in seawater has declined sufficiently. From this fact, it is pointed out that seabed sediment can be a source of radiocesium to coastal areas. In this study, behavior of dissolved radiocesium near the seafloor is discussed from the distributions of 137Cs in seawater, seabed sediment and pore water collected from the area around Fukushima. Between October 2015 and September 2017, seawater and surface (0~10 cm) sediments were collected at 17 stations at 1.5~105 km away from the Fukushima Daiichi Nuclear Power Plant. Seawater was collected at the surface layer (0~3 m depth), intermediate layer (5 m above the seabed), and the layer immediately on the seabed (overlying layer with 0.3 m in thickness). At four stations, pore water in sediment was also collected. The 137Cs concentration in seawater and sediment was measured by gamma-ray spectrometry. The 137Cs concentration in the overlying water ranged from 5 to 283 mBq L-1, and was 2~3 times higher than that in the intermediate layer water. The 137Cs concentration in the pore water was 33~1166 mBq L-1, which was 10~40 times higher than that in the overlying water. The 137Cs concentration in the overlying water did not show clear differences regardless of the pore size (0.45 μm, 0.2 μm and 1 kDa) of the filter used for filtration. From these results, it was confirmed that radiocesium in the seabed sediment was "dissolved" in pore water and diffused to the benthic layer. The 137Cs abundance in the pore water in the surface sediment corresponded to 0.1~0.6% of the 137Cs existing in the solid phase of sediment. At most stations, the 137Cs concentrations in the overlying water and the pore water were approximately proportional to those in the sediment. The apparent distribution coefficient between pore water and sediment was [0.9-4.2]×102 L kg-1, with no difference depending on the year of sampling. These results indicated that equilibrium of 137Cs between pore water and sediment has established in a relatively short period. From the above-mentioned results and kinetic parameters such as 137Cs desorption rate from sediment obtained from laboratory experiments, we estimated the mass balance of 137Cs in the sediments and the overlying water along the coast of Fukushima. The results showed that the 137Cs in the sediment was reduced by about 4~9% per year by desorption/diffusion of 137Cs from the seabed. This rate was lower than the reduction rate of 137Cs in sediments (~29%) observed in this region, and it was estimated that this process was not the main factor of decreasing the 137Cs inventory in sediments. In addition, as of 2017, since the 137Cs concentration presumed to migrate to benthos via the pore water will not exceed the regulatory limit of fishery products, the impact of supply to the benthic environment of 137Cs is considered to be limited. |
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| 会議概要（会議名, 開催地, 会期, 主催者等） | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | JPGU-AGU Joint Meeting 2018 | |||||
| 発表年月日 | ||||||
| 日付 | 2018-05-20 | |||||
| 日付タイプ | Issued | |||||
