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Takechi, Seiichi*; Tsuji, Hideki*; Koshikawa, Masami*; Ito, Shoko*; Funaki, Hironori; Hayashi, Seiji*
Rikusuigaku Zasshi, 82(1), p.1 - 16, 2021/02
Since the Fukushima Daiichi Nuclear Power Plant accident in 2011, soil minerals and organic matter including radiocesium have been deposited in the dam lakes near the nuclear power plant. There is concern that radiocesium will gradually leach from the lake bottom into the lake water, resulting in prolonged radioactive contamination of the freshwater ecosystems especially in downstream of the dams. In this study, we collected undisturbed sediment core samples at the center of the Yokokawa Dam lake in Fukushima Prefecture and suspended sediment in the inflowing river of the dam for 4 years and evaluated the amount of bioavailable form of radiocesium (exchanged, oxidized, and organic forms) in these samples by sequential extraction tests using the BCR method focusing on the temporal change.
Mochizuki, Akihito; Sasamoto, Hiroshi; Bamba, Daiya*; Ikigaki, Kayoko*
Rikusuigaku Zasshi, 81(2), p.153 - 166, 2020/05
Characterization of humic substances in groundwater are usually carried out using isolated humic substances from large volume of groundwater. However, the isolation process expends much time and effect, and such method is not available if the volume of groundwater collected is small. In this study, convenient characterization methods available to small volume of samples (3D-fluorescense analysis, Gel permeation chromatography and ion chromatography) were applied to groundwater and surface water in the Horonobe area, Hokkaido, to characterize dissolved organic matter (DOM) including humic substances. 3D-fluorescense spectrum obtained from small volume of groundwater was similar to those from isolated humic substances, and showed little variation with depth. However, the peak position of spectrum for surface water was different from those for groundwater. Gel permeation chromatography showed that DOM in groundwater mainly consists of humic substances with molecule weight of approximately 1,200
2,000 Da, and that the molecule weight decreases with depth. These results were consistent with the characteristics of isolated humic substances. Ion chromatography revealed that low molecule weight organic matter was minor component of DOM in the groundwater, which was consistent with the result of gel permeation chromatography. These results indicate that the methods applied in this study are useful for convenient characterization of DOM in groundwater.