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Direct and indirect effects of microbes on technetium insolubilization in paddy fields
https://repo.qst.go.jp/records/67986
https://repo.qst.go.jp/records/6798678a92a53-c4db-4075-8bf3-f8400eb50fed
| Item type | 会議発表用資料 / Presentation(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2004-12-17 | |||||
| タイトル | ||||||
| タイトル | Direct and indirect effects of microbes on technetium insolubilization in paddy fields | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_c94f | |||||
| 資源タイプ | conference object | |||||
| アクセス権 | ||||||
| アクセス権 | metadata only access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_14cb | |||||
| 著者 |
Ishii, Nobuyoshi
× Ishii, Nobuyoshi× Tagami, Keiko× Uchida, Shigeo× 石井 伸昌× 田上 恵子× 内田 滋夫 |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | The long-lived radionuclide, 99Tc, has been the object of considerable concern and attention for its environmental behavior and effects, because it has high mobility as the stable pertechnetate anion (TcO4-). In Asia, where people rice is a staple of the diet, the behavior of Tc in a paddy field has been a focal point. Previously, we found that most TcO4- was changed into insoluble forms in irrigated paddy soils and that living microorganisms could be responsible for the Tc insolubilization. However, it was not clear whether the insolubilization resulted from direct or indirect effects of microorganisms. In this study, we describe changes in the chemical or physical form of the Tc by cells of living microorganisms, by inorganic and organic particles, and by metabolites released from microorganisms. Since Tc released from radioactive waste disposal sites would move to paddy fields by irrigation water, physico-chemical reactions of the Tc in surface water on several soils were investigated. Seven soils, 5 g each, were cultured for 7 days at 25 ?C under a waterlogged condition. After collection of surface water of the samples, they were untreated or treated by filtration or autoclave, then, 95mTcO4- was added. The samples were incubated for 4 days at 25 ?C under an aerobic condition. To identify the chemical and physical forms of the Tc in the surface water, the following separations were carried out at the end of the incubation with the 95mTc: the sample was filtered with a 0.2-?m pore size filter to remove the insoluble Tc fraction, then the filtrate was passed through a TEVA resin (Eichrom) column to eliminate 95mTcO4- from the solution. Finally, cation forms of Tc in the eluate from TEVA column were fractionated with a cation exchange resin. Radioactivity of 95mTc in each fraction was measured with a NaI (Tl) scintillation counter. In the untreated surface water containing living microorganisms, 8.8% and 37.2% of the 95mTc were trapped on the 0.2-?m pore size filter membrane for two paddy field soil samples classified as Fluvisol, while less than 4.3% of the 95mTc was retained on the filter for the other samples. The maximum percentage of the 95mTc, which passed through the TEVA resin, was 2.3% for one of the Fluvisol samples. In fact, almost all of the 95mTc in the filtrate (< 0.2 ?m) was trapped on the TEVA resin. These results implied that living microorganisms in the surface water of Fluvisol had the ability to change the soluble TcO4- into insoluble forms by biosorption and bioaccumulation, and that they did not contribute to the transformation of free TcO4-. Inorganic and organic particles in autoclaved samples did not contribute to the insolubilization of the Tc, because more than 96.6% of the 95mTc was sorbed on the TEVA resin for all samples. The samples that were filtered before the addition of the 95mTc had no particles more than 0.2 ?m in diameter, but included metabolites derived from microorganisms. Most of the 95mTcO4- added to the filtrates, however, was not able to pass through the TEVA resin. This indicated that hardly any reduction of TcO4- occurred due to metabolites during incubation. In conclusion, some of living organisms directly contribute to the insolubilization of TcO4-. The extent of the chemical-physical transformation of Tc, however, is relatively slight in the surface water on paddy fields. Insolubilization of the TcO4- is probably caused in the soil phase and water-soil interface. |
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| 会議概要（会議名, 開催地, 会期, 主催者等） | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | Waste Management, Energy Security, and a Clean Environment | |||||
| 発表年月日 | ||||||
| 日付 | 2003-02-27 | |||||
| 日付タイプ | Issued | |||||
