ABSTRACT
Introduction ............................................................................................................................................ 522 Material and Methods ............................................................................................................................ 523
Physical and Chemical Analyses...................................................................................................... 523 Mineralogical Analysis..................................................................................................................... 523 SEM-EDX Observation.................................................................................................................... 523 Demonstration Experiments at Paddy Field in Baba........................................................................ 523
Results.................................................................................................................................................... 526 Chemical Composition and Radionuclide in Paddy Soils................................................................ 526 Demonstration Paddy Field in Baba................................................................................................. 527 Chemical Point Analysis................................................................................................................... 527 Chemical Analysis of Diatomaceous Earth...................................................................................... 527 Mineralogical Analysis of Diatomaceous Earth............................................................................... 529 pH and EC of Diatomaceous Earth in Noto...................................................................................... 529 H2O2 Treatment of Paddy Soil in Baba and Absorption Test of Diatomaceous Earth in Noto ......... 530 Electron Microscopic Observation of Diatomaceous Earth before Experiment ................................531 SEM-EDX Observation of Diatomaceous Earth in Noto, after One-Year Experimental Demonstration....................................................................................................................................533 Schematic SEM-EDX Data of Diatomaceous Earth in Noto, after One-Year Experimental Demonstration....................................................................................................................................539
Discussion...............................................................................................................................................539 Clay Minerals: Radionuclide Interactions.........................................................................................539 Microorganisms-Radionuclides Interaction..................................................................................... 540 Concentration of 237Np .......................................................................................................................541 Biomineralization and Bioremediation ............................................................................................. 542 Radioactive Waste............................................................................................................................. 542 Acidic Condition of Diatomaceous Earth......................................................................................... 542
Conclusions............................................................................................................................................ 542 Acknowledgments.................................................................................................................................. 543 References.............................................................................................................................................. 543
Diatomaceous earth collected from Noto Peninsula, Ishikawa Prefecture, was observed by scanning electron microscopy (SEM) equipped with energy dispersive x-ray analyzer (EDX). These samples had suffered radiation exposure in a radioactive paddy ‹eld in Baba, Fukushima Pref., Japan, after the Great East Japan Earthquake, on March 11, 2011. Energy-dispersive x-ray ”uorescence (ED-XRF) analysis and Ge semiconductor detector found not only major elements but also radionuclides, such as 134Ce, 137Cs, 89Sr, and 90Sr, in the paddy ‹eld in Baba. After 1 year, SEM-EDX quantitative analyses of diatoms and clay minerals (mainly montmorillonite) clearly indicated concentration of radionuclide, such as I, Cs, Ba, Nd, Th, U, Np, and Pu, suggesting absorption of both radionuclide and stable isotope elements from radioactive polluted paddy soils. The leak of radioactivity of 137Cs, part of 90Sr, and the traces of some radionuclide are originated from Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. The diatom-clays-radionuclide interaction in the polluted paddy soils in Fukushima could be effective as the shield for low-level radioactive waste at the geological disposal.
