阿武隈川支流の堤外地表層における<sup>137</sup>Cs濃度の経時的変化  [in Japanese] Temporal Changes in <sup>137</sup>Cs Concentrations in the Surface Soil of Flood Channel at Abukuma River Tributaries  [in Japanese]

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Abstract

2012年から2014年にかけて, 福島県を流れる阿武隈川の2次支流である石田川 (根古屋) と, 1次支流である広瀬川 (界) の堤外地において, 表層底質の<sup>137</sup>Cs蓄積状況の変化を調査した。調査では, 同一地点の<sup>137</sup>Cs蓄積量の変化と河床の微地形変化を調べるため, 動的干渉測位 (RTK) GPSを用いた。福島第一原子力発電所の事故以降2014年の調査までに, 根古屋では完全に11回, 界では部分的に3回程度高水敷は冠水し, それを受け, 堤外地表層の<sup>137</sup>Cs蓄積量は上流域よりも大きく低下した。つまり, <sup>137</sup>Cs蓄積量は, 根古屋では2012年から2014年に72±21%, 界では2013年から2014年に59±34%低下した。しかし, 根古屋は堆積地であり, 濃度は表層下30cmにかけて増加したことから, 出水時に河川に流出した<sup>137</sup>Cs濃度の低い土砂が, 高濃度の<sup>137</sup>Csを下層に埋没させたと考えられた。

We investigated temporal changes in <sup>137</sup>Cs concentrations in the surface soil of flood channels at a primary tributary (site name, Sakai) and a secondary tributary (site name, Nekoya) of Abukuma River from 2012 to 2014. In this study, we employed a real-time kinematic global positioning system (RTK-GPS) to collect samples from pinpoint locations, and to survey the microtopographical change at the monitoring sites. The flood channel of Nekoya was considered to have been completely inundated about 11 times, while Sakai had been partially inundated a few times during the survey period. <sup>137</sup>Cs concentrations in the surface sediments (0–5 cm) were decreased faster than those in the watershed by inundation (s) . Specifically, <sup>137</sup>Cs concentrations (Bq m<sup>-2</sup>) decreased by 72 ± 21% at Nekoya from 2012 to 2014, and by 59 ± 34% at Sakai from 2013 to 2014. However, <sup>137</sup>Cs concentrations in the flood channel of Nekoya increased at a deeper horizon up to 30 cm. This result suggested that sediment with higher <sup>137</sup>Cs concentration was buried by that with lower <sup>137</sup>Cs concentration eroded during flood events.

Journal

  • Journal of Japan Society on Water Environment

    Journal of Japan Society on Water Environment 39(5), 171-179, 2016

    Japan Society on Water Environment

Codes

  • NII Article ID (NAID)
    130006883012
  • Text Lang
    JPN
  • ISSN
    0916-8958
  • Data Source
    J-STAGE 
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