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A large amount of radiocesium was released from the accident at Fukushima Daiichi Nuclear Power Plant of Tokyo Electric Power Company. The determination of dissolved and particulate radiocesium concentrations in water is important, which can be used as basic information for understanding the long-term radiocesium dynamics in the environment and the transfer of radiocesium to crops. Conventional quantitative methods include the evaporative concentration to the dryness method and the AMP method. These methods need to concentrate about 20–200 L of water due to the low concentration of the dissolved radiocesium. After the accident, several new methods, such as the Prussian blue filter cartridge method and the solid-phase disk method, have been developed and put to practical use. In this study, we carried out an accuracy evaluation test to assess five methods (i.e., the evaporative concentration to dryness method, the AMP method, the Prussian blue filter cartridge method, the solid-phase disk method, and the ion-change resin method) using 3 types of water samples containing 0.01-1.0 Bq L−1 of dissolved radiocesium. Our results showed that the z-scores of over 80 % of the measured data were within ±2 and their CVs in the range of 8-13 %, indicating good reproducibility of these methods.

Most of radioactive material released from Abukuma River Basin, one of the largest stream near the contaminated zone of Fukushima, flowing most of the contaminated plane zone then flow into the Pacific Ocean, are in the suspended particulate form, being estimated more than 90 % in the upper stream and 70% near the river mouth. Most of radionuclides in particulate form are still trapped bottom sediment in the middle of the basin, however we find that significant amount are released during the heavy precipitation event. We also found that, at hydrological extremes the total loading increase more than 1000 times higher than the normal stream condition. The total flux of radiocesium into the Pacificic Ocean estimated at the Iwanuma Station from 10 August 2011 to 10 May 2012 become 9.11 Terabecquerel during 274 days for [137]Cs, and 6.81 Terabecquerel during 274 days for [134]Cs.

金沢大学環日本海域環境研究センター, The Japanese Forest Society Congress 120, Session ID : Pc2-09

福島新田川流域には原発事故直後に大量の放射性セシウム137が大気経由で沈着し，河道に集積した高濃度の懸濁態137Csが出水毎に間欠的に海域へ供給され，沿岸域の底質環境に影響を与え続けている．本研究では，4段ネストJCOPE2-ROMS海洋モデル，多粒径3次元土砂輸送モデル，波浪推算モデルSWAN，河道モデルiRIC-Nays2DH，放射性核種吸着モデルを連成させた超高解像度広域土砂・懸濁態137Cs海洋分散モデリングを行い，台風201326号出水イベントに伴う河川起源土砂の河口・沿岸域における堆積・浸食状況の時空間特性を評価した．さらに懸濁態137Csインベントリ解析を行い，水深5 mまでの河口域，水深10mまでの河口外縁域での堆積，沿岸漂砂等による河川起源137Csの海域堆積層への移行特性を定量化した．

起伏が大きく、地質の異なる３つの小流域で、流出量、電気伝導度を連続観測した。また、自動採水装置で降雨時の河川水を採取し、水質分析を行った。なお、それぞれの流域の流域面積・起伏比などの地形条件や、植生や斜面物質などの条件はほぼ等しい。1993年の観測の結果、流出率やイベントの減衰の仕方、イベント発生の敏感さなど3流域で異なる結果を得た。中古生層地域のK1流域は、流出率が大きく、減衰が遅い流出が起こる。しかし降雨量が少ないときには流出が起きなかったり、起きても流出率がほとんど0％である。また、1つのイベントに、降雨と同時に発生する極めて小さな1次ピークと、平均9時間程度遅れて発生する大きな2次ピークとが存在する。花崗岩地域のY1流域は、ピーク流量が大きく、かつ減衰が速く、降雨に対して敏感な鋭い流出が発生する。変成岩地域のO1流域は、ピーク流量が小さく、減衰が速く、流出量が小さいという、流出反応が全体的に小さい特性を持つ。ハイドログラフおよび水質の特徴から、これらの流域では、表面流は主な流出成分ではない可能性が高いことが示唆された。したがって、流出特性の違いは、地質の違いによる地中での水の挙動の違いを示唆する。, Hydrological observations were conducted in the small (3.8-7.1ha) steep forested watersheds where three types of bedrocks are underlain (Paleozoic sedimentary rocks, Granite, Metamorphic rocks). A contrasting runoff response to rainfall was observed. In K1 watersheds (sedimentary rocks), runoff did not respond to each rainfall, occurring only at the high antecedent rainfall condition. Double peak hydrographs, having very low initial peak and high secondary peak, were observed. Contrary to this, in Y1 watershed (Granite), frequent runoff events with high discharge peak were observed, and the quick flow runoff ratio was proportional to the amount of rainfall. In O1 watershed (Metamorphic rocks), the runoff response is similar to Y1 watershed, but the quick flow runoff ratio was much smaller. From the above results, it is suggested that these differences were caused by different storm water flow paths due to different underlying geology., 農林水産研究情報センターで作成したPDFファイルを使用している。

1990