RI imaging method to analyze a process of radiocesium contamination of plants and to develop phytoremediation techniques

RIイメージング技術を用いた植物中セシウムの動態と解析とファイトレメディエーション技術の開発

河地 有木; 尹 永根; 鈴井 伸郎; 石井 里美; 渡部 浩司*; 山本 誠一*; 藤巻 秀

Kawachi, Naoki; Yin, Y.-G.; Suzui, Nobuo; Ishii, Satomi; Watabe, Hiroshi*; Yamamoto, Seiichi*; Fujimaki, Shu

Because of the accident at the Fukushima Daiichi Nuclear Power Plant of the Tokyo Electric Power Company, Inc., an extensive area of agricultural fields was contaminated with radioactive materials. Cs-137 is the most of soil contaminant, which was reported to have a 16 - 18 years half-life in agricultural fields affected by physical decay and soil erosion. Therefore, further research is required on the behavior of radiocesium and its transfer from contaminated soil to agricultural products. In this study, we have developed a gamma camera for ray imaging of Cs-137 emitting at 662 keV. A pinhole collimator was fabricated with heavy metal of tungsten to avoid the penetration and scattering of rays, since high-energy incident ray originates from Cs-137 tracer inside a test plant. A gadolinium oxyorthosilicate (GSO) scintillator and a flat panel position sensitive photomultiplier tube were adapted to the gamma camera to obtain adequate high sensitivity. Giant knotweed, which has potential as a cleanup plant with high uptake capacity for cesium, was grown in hydroponic solutions. After exposed to approximately 400 kBq of Cs-137, images were taken for 15 h. Sequential images reveal the changing distribution of cesium into the plant from the hydroponic solutions via the root system. We have indicated real-time visualization of uptake of radiocesium within an intact plant in the first time successfully.