Dynamics of Tc Immobilization in Soils Under Flooded Conditions and Extent of Reoxidation Following Aeration

Abstract

The dynamics and bioavailability of ⁹⁹Tc, an important radioactive contaminant, depend largely on its redox state. Both biotic and abiotic reactions determine the rate, extent and reversibility of Tc immobilization. We monitored Tc solubility and chemical extractability in five contrasting soils. Tc remained water-soluble in aerated soils, but was immobilized under flooded conditions. Immobilization was only partly reversible. Immobilized Tc was associated with soil organic matter and was possibly chemically reduced in one soil. Water solubility was a sensitive probe of Tc dynamics. The extent of immobilization and reversibility were not simple functions of soil chemical or biological properties.

Keywords:

• technetium
• soil
• soil water conditions
• immobilization
• reoxidation

ACKNOWLEDGMENTS

The authors thank Pierre Hurtevent, Thomas Perrier and Daniel Orjollet for their technical assistance and Marcel Morello for his help with liquid scintillation counting.