Rhenium As a Surrogate for Technetium in Soil Partitioning Experiments.

Technetium (Tc), a nuclear fission product with no stable isotopes, represents much of the long-term radioactivity associated with nuclear waste. Under oxidizing conditions, Tc persists in the environment as the pertechnetate anion (TcO₄^-), with Tc in the +7 oxidation state.  As an anion, pertechnetate is generally assumed to sorb poorly to most soil materials. To avoid the use of radioactive materials, Rhenium (Re) is often used as a chemical surrogate for Tc in soil partitioning experiments.  Like Tc, Re generally persists in the +7 oxidation state as the perrhenate anion (ReO₄^-) under oxidizing conditions. In the current study, Re partitioning to highly weathered soils from the southeastern US was evaluated in a series of laboratory batch and dynamic column experiments. While little sorption was observed for surface soil materials (A horizon), Re was significantly retarded in subsoil materials that contain appreciable Fe oxides.