Movement of radiocaesium fallout released by the 2011 Fukushima nuclear accident

Koji Minoura, Tsutomu Yamada, Shin ichi Hirano, Shinji Sugihara

研究成果: ジャーナルへの寄稿学術誌査読

8 被引用数 (Scopus)

抄録

The moment magnitude (M w) 9.0 Tohoku-Oki Earthquake occurred on March 11, 2011, generating an unusually large tsunami. The seismic shocks and tsunami inundation severely damaged the Fukushima Daiichi Nuclear Power Plant. Radionuclide emission due to reactor breakdown contaminated wide areas of Fukushima and its surroundings. Heavy rainfall causes runoff across surface soil, and fine soil particles are susceptible to uptake by the flowing water. The high radioactivity of grains suspended in floodwater indicates that radioactive fallout was streamed into rivers in particulate form and transported downstream under high-flow conditions. Here, we investigated the diachronic mode of 134Cs and 137Cs in central Fukushima, through which the contaminated air mass drifted and caused wet deposition of radionuclides. Stratigraphic measurements of radioactivity in sediment cores is the method employed in this study to determine the basin-wide movement of 134Cs and 137Cs, to evaluate the significance of the erosion-transportation-accumulation processes on natural decontamination in terrain characterized by steep slopes and high precipitation. Stratigraphic results illustrate the process of fluvial sediment discharge, and the massive deposition of radiocaesium suggests basin-wide movement of fallout during concentrated rainfall. Grain suspension in torrential currents is an important pathway for transportation of radionuclides from land to sea, and the appearance of hotspots on floodplains and the offshore sea floor is the consequence of erosion and transportation under seasonal heavy precipitation. Radioactive horizons occur in offshore sediment columns and thus radiocaesium discharged from the estuary will persist forever under the sea floor if no artificial disturbance occurs.

本文言語英語
ページ(範囲)1843-1862
ページ数20
ジャーナルNatural Hazards
73
3
DOI
出版ステータス出版済み - 8月 2014

!!!All Science Journal Classification (ASJC) codes

  • 水の科学と技術
  • 大気科学
  • 地球惑星科学(その他)

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