Migration of uranium(IV)/(VI) in the presence of humic acids in quartz sand: a laboratory column study.
The migration behavior of U(IV) and U(VI) in the presence of humic acid was studied in a quartz sand system. Laboratory column experiments were performed using humic acid, U(VI) in humic acid absence, U(IV) and U(VI) in humic acid presence, and for comparison a conservative tracer. In experiments using humic acid, both redox species of U migrate nearly as fast as the conservative tracer. Humic acid accelerates the U(VI) breakthrough compared to the humic acid-free system. There are strong indications for a similar effect on the U(IV) transport. At the same time, a part of U(IV) and U(VI) associated with the humic acid is immobilized in the quartz sand due to humic colloid filtration thus producing a delaying effect. Tailing at a low concentration level was observed upon tracer elution. The experimental breakthrough curves were described by reactive transport modeling using equations for equilibrium and kinetic reactions. The present study demonstrates that humic acids can play an important role in the migration of actinides. As natural organic matter is ubiquitous in aquifer systems, the humic colloid-borne transport of actinides is of high relevance in performance assessment.
Mibus
Jens
J
Forschungszentrum Rossendorf e.V., Institute of Radiochemistry, PO Box 510 119, D-01314 Dresden, Germany. j.mibus@fz-rossendorf.de
Sachs
Susanne
S
Pfingsten
Wilfried
W
Nebelung
Cordula
C
Bernhard
Gert
G
D002845:Chromatography; D006812:Humic Substances; D010084:Oxidation-Reduction; D011791:Quartz / Q000737:chemistry*; D011849:Radioactive Tracers; D012822:Silicon Dioxide / Q000737:chemistry*; D012990:Soil Pollutants, Radioactive; D014501:Uranium; D014872:Water Movements; D014875:Water Pollutants, Radioactive
D006812:Humic Substances; D011849:Radioactive Tracers; D012990:Soil Pollutants, Radioactive; D014875:Water Pollutants, Radioactive; D011791:Quartz; D014501:Uranium; D012822:Silicon Dioxide