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Radionuclide Movement during Unsteady, Unsaturated Soil Water Flow

Published online by Cambridge University Press:  21 March 2011

D.E. Smiles  and
G.D. McOrist
D.E. Smiles
Affiliation:
CSIRO Land and Water, PO Box 1666, Canberra ACT 2601, Australia
G.D. McOrist
Affiliation:
Australian Nuclear Science & Technology Organization, PMB 1, Menai NSW 2234, Australia. Email: david.smiles@cbr.clw.csiro.au
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Abstract

Absorption of aqueous solution by soil appears to result in piston-like displacement of the soil solution originally present by the invading solution. Diffusive redistribution of non-reactive solutes, relative to the water, occurs about that front when the solutions are of different chemical constitution. Adsorption of solute by the soil solid retards the solute front relative to the piston- front; it also reduces the effective diffusivity of the solute relative to the water. Such behavior tests prediction of radionuclide transport and retardation during non-steady water flow in unsaturated soil based on measured distribution coefficients.

Experiments, where initially uniform soil columns absorbed tritiated water containing 60Co2+ from a source at constant water potential, illustrate these effects. Columns were sampled at significantly different elapsed times and the transient water content, water soluble salts, tritium and cobalt profiles determined. Theory anticipates, and experiment confirms, self- similarity of these profiles when data is graphed in terms of distance divided by the square root of time. Water, and soil solid-based, material coordinates facilitate data analysis; measurement of absorption isotherms is also discussed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 663: Symposium – Scientific Basis for Nuclear Waste management XXIV , 2000 , 1117
Copyright
Copyright © Materials Research Society 2001

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References

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