WEKO3
アイテム
Influence of microbial community on the behaviors of technetium and other trace elements in water covering rice paddy soils
https://repo.qst.go.jp/records/67463
https://repo.qst.go.jp/records/674636b480eaa-a646-4d44-a8cd-ff1305fea1c6
| Item type | 会議発表用資料 / Presentation(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2003-09-11 | |||||
| タイトル | ||||||
| タイトル | Influence of microbial community on the behaviors of technetium and other trace elements in water covering rice paddy soils | |||||
| 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× Enomoto, Shuichi× Uchida, Shigeo× 石井 伸昌× 田上 恵子× 内田 滋夫 |
|||||
| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | The release of radionuclides into the environment is a subject of public concern. Technetium-99 (99Tc) is a radioactive contaminant in the environment and has been accumulating because of its long half-life of 2.1 x 10E+5 y. This radionuclide is highly soluble and available for plants under aerobic conditions as TcO4-, but the reduced form of Tc, Tc(IV), is insoluble and biological inactive. Some anaerobic microorganisms have been shown to reduce TcO4- to insoluble Tc(IV) through their anaerobic energy metabolism. Generally, such bacteria are found in soils under waterlogged conditions, i.e. paddy fields. Chemical behavior of Tc in water covering paddy field soils, however, is not well known. In this study, we pay attention on the insolubilization of Tc by the activity of microbial community in the water body of waterlogged soils. Furthermore insolubilizations of other trace elements were also studied because the microbial community insolubilized Tc could affect on the fate of other trace elements as well. First, microbial communities in soils were checked their abilities of Tc insolubilization from TcO4-. Nine paddy field soil samples were flooded with 0.3% glucose water and incubated for 7 days. After the incubation, the water covering the soil sample was transferred into a new test tube, and 95mTcO4- was added to the tube as a radiotracer. At 4 days after the addition of 95mTc, the solution was separated into four fractions, that is, insoluble-Tc, pertechnetate, cationic-Tc, and Tc in other forms, by passing the solution through a 0.2 micro m-pore-size membrane filter, a TEVA resin column, and a cation exchange resin column. The results showed that the dominant Tc chemical form in most of the samples was TcO4-. However, on average, 16.9% of the added 95mTcO4- changed to insoluble forms and the maximum Tc insolubilization, 76.2 +/- 9.2%, was found in a soil (P38). When the P38 sample was subjected to further studies, it was observed that the insolubilization percentage was decreased to 3.6 +/- 0.5% by removing microorganisms from the water body, and the percentage was also decreased to 23.4 +/- 0.8% by adding antibiotics to depress metabolism of bacteria. These results suggested that TcO4- could be insolubilized in the water covering soils by living bacteria. Then, the behaviors of trace elements in water covering P38 were also studied using the same method. To trace elements, a multitracer solution produced in RIKEN Ring Cyclotron was added to the tubes. The multitracer solution included the following short-lived radionuclides: 7Be, 46Sc, 75Se, 83Rb, 85Sr, 88Y, 95Nb. 95mTc, 139Ce, 143Pm, 153Gd, 169Yb, 175Hf, and 183Re. After 4 days of the incubation with the multitracers, the culture was sequentially separated into 4 fractions as described in above. The radioactivities in the fractions were analyzed using a Ge detecting systems (Seiko EG &G). For the elements except Rb, Sr, and Re, more than 80% of the elements were trapped by the membrane filter, while >70% of Rb and Sr were retained in the cation resin column. Rhenium is a congener of Tc in the group VIIa, but 28.2 +/- 1.9% of Re was trapped by the membrane filter. Most of Re was trapped on the TEVA resin. The high retention ratios of trace elements by the membrane filtration indicated that the Tc insolubilizing microbial community would be applied for biological treatment of 99Tc and other trace elements/radionuclides by fixing them in the environment. |
|||||
| 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 | 第16回 International Symposium on Environmental Biogeochemistry | |||||
| 発表年月日 | ||||||
| 日付 | 2003-09-06 | |||||
| 日付タイプ | Issued | |||||
