title: Immobilization of cesium-137 and uranium in contaminated sediments using soil amendments.
abstract: Batch and dynamic leaching methods were used to evaluate the effectiveness of hydroxyapatite (HA), illite, and zeolite, alone and in combination, as soil additives for reducing the migration of cesium-137 (137Cs+) and uranium (U) from contaminated sediments. Amendment treatments ranging from 0 to 50 g kg(-1) were added to the sediment and equilibrated in 0.001 M CaCl2. After equilibration, the treatment supernatants were analyzed for 137Cs+, U, PO4, and other metals. The residual sediments were then extracted overnight using one of the following: 1.0 M NH4Cl, 0.5 M CaCl2, or the Toxicity Characteristic Leaching Procedure (TCLP) extractant. Cesium was strongly sorbed to the contaminated sediments, presumably due to interlayer fixation within native illitic clays. In fact, 137Cs+ was below detection limits in the initial equilibration solutions, the CaCl2 extract, and the TCLP solution, regardless of amendment. Extractants selective for interlayer cations (1.0 M NH4Cl) were necessary to extract measurable levels of 137Cs+. Addition of illitic clays further reduced Cs+ extractability, even when subjected to the aggressive extractants. Zeolite, however, was ineffective in reducing Cs+ mobility when subjected to the aggressive extractants. Hydroxyapatite was less effective than illite at reducing NH4+-extractable Cs+. Hydroxyapatite, and mixtures of HA with illite or zeolite, were highly effective in reducing U extractability in both batch and leaching tests. Uranium immobilization by HA was rapid with similar final U concentrations observed for equilibration times ranging from 1 h to 30 d. The current results demonstrate the effectiveness of soil amendments in reducing the mobility of U and Cs+, which makes in-place immobilization an effective remediation alternative.
authors.affiliation: Advanced Analytical Center for Environmental Sciences, Savannah River Ecology Lab, Univ of Georgia, Aiken, SC 29802, USA. seaman@srel.edu
authors.forename: J C
authors.initials: JC
authors.lastname: Seaman
authors.forename: T
authors.initials: T
authors.lastname: Meehan
authors.forename: P M
authors.initials: PM
authors.lastname: Bertsch
mesh_terms: D002588:Cesium Radioisotopes / Q000032:analysis / Q000737:chemistry; D017886:Durapatite / Q000737:chemistry; D004784:Environmental Monitoring; D004787:Environmental Pollution / Q000517:prevention & control; D019015:Geologic Sediments / Q000737:chemistry; D008903:Minerals / Q000737:chemistry; D012990:Soil Pollutants, Radioactive / Q000032:analysis*; D014501:Uranium / Q000032:analysis* / Q000737:chemistry; D017641:Zeolites / Q000737:chemistry
chemical_list: D002588:Cesium Radioisotopes; D008903:Minerals; D012990:Soil Pollutants, Radioactive; C099089:illite; D017641:Zeolites; D014501:Uranium; D017886:Durapatite