Lusa M, Bomberg M, Virtanen S, Lempinen J, Aromaa H, Knuutinen J, Lehto J
Laboratory of Radiochemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, 00014 Helsinki, Finland.
VTT Technical Research Centre of Finland, P.O. Box 1000, 02044 VTT, Finland.
J Environ Radioact. 2015 Sep;147:22-32. doi: 10.1016/j.jenvrad.2015.05.005. Epub 2015 May 23.
(135)Cs is among the most important radionuclides in the long-term safety assessments of spent nuclear fuel, due to its long half-life of 2.3 My and large inventory in spent nuclear fuel. Batch sorption experiments were conducted to evaluate the sorption behavior of radiocesium ((134)Cs) in the surface moss, peat, gyttja, and clay layers of 7-m-deep profiles taken from a nutrient-poor boreal bog. The batch distribution coefficient (Kd) values of radiocesium increased as a function of sampling depth. The highest Kd values, with a geometric mean of 3200 L/kg dry weight (DW), were observed in the bottom clay layer and the lowest in the 0.5-1.0 m peat layer (50 L/kg DW). The maximum sorption in all studied layers was observed at a pH between 7 and 9.5. The in situ Kd values of (133)Cs in surface Sphagnum moss, peat and gyttja samples were one order of magnitude higher than the Kd values obtained using the batch method. The highest in situ Kd values (9040 L/kg DW) were recorded for the surface moss layer. The sterilization of fresh surface moss, peat, gyttja and clay samples decreased the sorption of radiocesium by 38%, although the difference was not statistically significant. However, bacteria belonging to the genera Pseudomonas, Paenibacillus, Rhodococcus and Burkholderia isolated from the bog were found to remove radiocesium from the solution under laboratory conditions. The highest biosorption was observed for Paenibacillus sp. V0-1-LW and Pseudomonas sp. PS-0-L isolates. When isolated bacteria were added to sterilized bog samples, the removal of radiocesium from the solution increased by an average of 50% compared to the removal recorded for pure sterilized peat. Our results demonstrate that the sorption of radiocesium in the bog environment is dependent on pH and the type of the bog layer and that common environmental bacteria prevailing in the bog can remove cesium from the solution phase.
（135）由于铯的半衰期长达230万年且乏核燃料中存量大，它是乏核燃料长期安全评估中最重要的放射性核素之一。开展了批量吸附实验，以评估放射性铯（（134）Cs）在取自贫营养北方沼泽7米深处剖面的表层苔藓、泥炭、腐殖土和黏土层中的吸附行为。放射性铯的批量分配系数（Kd）值随采样深度增加。在底部黏土层观察到最高的Kd值，几何平均值为3200升/千克干重（DW），在0.5 - 1.0米泥炭层中最低（50升/千克DW）。在所有研究层中，pH值在7至9.5之间时观察到最大吸附量。表层泥炭藓、泥炭和腐殖土样品中（133）Cs的原位Kd值比采用批量法获得的Kd值高一个数量级。表层苔藓层记录到最高的原位Kd值（9040升/千克DW）。新鲜表层苔藓、泥炭、腐殖土和黏土样品的灭菌处理使放射性铯的吸附减少了38%，尽管差异无统计学意义。然而，从沼泽中分离出的假单胞菌属、芽孢杆菌属、红球菌属和伯克霍尔德菌属细菌在实验室条件下能从溶液中去除放射性铯。芽孢杆菌属V0 - 1 - LW菌株和假单胞菌属PS - 0 - L菌株的生物吸附量最高。当将分离出的细菌添加到灭菌的沼泽样品中时，与纯灭菌泥炭相比，溶液中放射性铯的去除量平均增加了50%。我们的结果表明，沼泽环境中放射性铯的吸附取决于pH值和沼泽层类型，且沼泽中普遍存在的常见环境细菌能从液相中去除铯。
