title: Factors affecting the sorption of cesium in a nutrient-poor boreal bog.
abstract: (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.
authors.affiliation: Laboratory of Radiochemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, 00014 Helsinki, Finland. Electronic address: merja.lusa@helsinki.fi.
authors.forename: M
authors.initials: M
authors.lastname: Lusa
authors.affiliation: VTT Technical Research Centre of Finland, P.O. Box 1000, 02044 VTT, Finland.
authors.forename: M
authors.initials: M
authors.lastname: Bomberg
authors.affiliation: Laboratory of Radiochemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, 00014 Helsinki, Finland.
authors.forename: S
authors.initials: S
authors.lastname: Virtanen
authors.affiliation: Laboratory of Radiochemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, 00014 Helsinki, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Lempinen
authors.affiliation: Laboratory of Radiochemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, 00014 Helsinki, Finland.
authors.forename: H
authors.initials: H
authors.lastname: Aromaa
authors.affiliation: Laboratory of Radiochemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, 00014 Helsinki, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Knuutinen
authors.affiliation: Laboratory of Radiochemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, 00014 Helsinki, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Lehto
mesh_terms: D000327:Adsorption; D002588:Cesium Radioisotopes / Q000378:metabolism*; D005387:Finland; D006863:Hydrogen-Ion Concentration; D012990:Soil Pollutants, Radioactive / Q000378:metabolism*; D014875:Water Pollutants, Radioactive / Q000378:metabolism*; D053833:Wetlands
chemical_list: D002588:Cesium Radioisotopes; D012990:Soil Pollutants, Radioactive; D014875:Water Pollutants, Radioactive
keywords: Bacteria; Cesium; Peat; Radioactive waste; Radionuclides; Sorption