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Erosion and Redeposition of Sediments and Sediment-Associated Radiocesium on River Floodplains (the Niida River Basin and the Abukuma River as an Example)статья
- Авторы: Golosov Valentin, Konoplev Alexei, Wakiyama Yoshifumi, Ivanov Maxim, Komissarov Mikhail
- Сборник: Behavior of Radionuclides in the Environment III
- Глава в коллективной монографии
- Год издания: 2022
- Издательство: Springer Singapore
- Местоположение издательства: Singapore
- Первая страница: 97
- Последняя страница: 133
- DOI: 10.1007/978-981-16-6799-2_7
- Аннотация: This chapter deals with the features of sediment-associated 137Cs accumulation and erosion on the river floodplains in the Fukushima-affected area. Evaluation of 137Cs inventories changes on different floodplain levels that were studied in the Niida River basin and along the valley bottom of the Abukuma River. The Niida River basin is the typical small river with high level of initial radionuclide contamination after explosion at Fukushima Daiichi NPP in the upper part of the basin. The Abukuma River is the largest river of the Northern half of the Honshu island with medium level of the initial radionuclide contamination in the part of the basin. Seven and six floodplain cross sections were studied in different types of river parts in the Niida River basin and at the Abukuma River floodplain, respectively. The combination of the different techniques, including analysis of the 137Cs depth distribution curves, evaluation of the sediment and sediment-associated 137Cs at the artificial plastic lawn-grass mats, and assessment of river bottom transformation based on space image interpretations and field survey with measurement of air dose rates, was used for understanding the transformation of the floodplain contamination level after ordinary and extreme floods. It was found that sediment-associated 137Cs sedimentation rates are strongly dependent on the type of the river bottom. The river channel gradient in the river reach located upstream from the studied floodplain cross section is the key parameter influencing the amount of sediment accumulated. The thickness of the “fresh” sediment accumulated on the floodplain in the case of ordinary flood is in the range of 1–5 cm, while up to 40–50 cm of sediment are accumulated in some floodplain sections during the extreme floods associated with typhoons Etau and Hagibis. The high rates of sediment accumulation on the floodplains of rivers in the Fukushima contamination zone contribute to a decrease in the air dose rate within the river valley bottoms with high levels of initial contamination due to the accumulation of “cleaner” sediments with relatively low 137Cs concentrations. On the other hand, the transfer of sediments contaminated with radionuclides and their redeposition in floodplain areas with low levels of initial contamination contributes to the expansion of territories with increased 137Cs inventories.
- Добавил в систему: Голосов Валентин Николаевич