title: Effect of redox potential on fixation of 137Cs in lake sediment.
abstract: Fixation of 137Cs was determined in lake sediment suspensions under controlled redox potentials in the laboratory. The activity of previously added 137Cs on various clay sites was determined by time-series selective extractions. Monovalent cations, particularly NH+4, were much more effective at displacing 137Cs than divalent cations or Na+. Ammonium ion (NH+4) and Na+ were used to extract 137Cs from selective and non-selective 137Cs-binding sites, respectively. The activity of water-soluble 137Cs and Na-extractable 137Cs was significantly higher under anaerobic redox conditions (-200 mV), when soluble NH+4 concentrations in the anaerobic suspensions were 1000 microM or higher. Activities of 137Cs were highest (initially 40-50% of the 137Cs added) on the NH+4-extractable site. Over the long term, activities of NH+4-extractable 137Cs decreased linearly to below 10% as 137Cs was fixed on inter-lattice sites. Water-soluble 137Cs was significantly correlated with Na-extractable 137Cs in short-term experiments, suggesting the existence of an equilibrium between the different clay sites. High concentrations of NH+4 under anaerobic redox conditions could shift this equilibrium, resulting in increases in water-soluble 137Cs and increases in the activities of 137Cs bound on non-selective clay sites. Additional studies are necessary to evaluate the interaction of 137Cs with sulfides, iron oxides, and other reactive chemical species which may attenuate 137Cs in sediment.
authors.affiliation: Laboratory for Wetland Soils and Sediments, Louisiana State University, Baton Rouge 70803-7511.
authors.forename: J H
authors.initials: JH
authors.lastname: Pardue
authors.forename: R D
authors.initials: RD
authors.lastname: DeLaune
authors.forename: W H
authors.initials: WH
authors.lastname: Patrick
authors.forename: J H
authors.initials: JH
authors.lastname: Whitcomb
mesh_terms: D002588:Cesium Radioisotopes; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D012989:Soil Pollutants; D012990:Soil Pollutants, Radioactive; D014873:Water Pollutants; D014875:Water Pollutants, Radioactive
chemical_list: D002588:Cesium Radioisotopes; D012989:Soil Pollutants; D012990:Soil Pollutants, Radioactive; D014873:Water Pollutants; D014875:Water Pollutants, Radioactive