Plutonium Sorption over 10 Orders of Magnitude
Plutonium (Pu) adsorption to and desorption from mineral surfaces plays a major role in controlling its mobility in the environment. However, laboratory measurements of Pu sorption are typically conducted at much higher concentrations (10-6 to 10-10 M) than found in subsurface water (< 10-12 M). As a result, there is a concern that Pu behavior determined in lab measurements might not be representative of sorption occurring under actual subsurface conditions. A new study carried out at Lawrence Livermore National Laboratory (LLNL) overcomes this obstacle. It provides measurements of the sorption of dissolved Pu (V) onto surfaces of a common clay mineral (Na-montmorillonite) over an unprecedentedly large range of initial plutonium solution concentrations (10-6 to 10-16 M). Concentration measurements at the low end of this range were made possible by the unique capabilities of the Center for Accelerator Mass Spectrometry at LLNL. The team’s results indicate that the plutonium adsorption behavior on montmorillonite was linear over the range of concentrations studied, indicating that plutonium sorption behavior from laboratory studies at higher concentrations can be extrapolated to sorption behavior at low, environmentally relevant concentrations.
Begg, J., M. Zavarin, P. Zhao, S. Tumey, B. A. Powell, and A. B. Kersting. 2013. “Pu(V) and Pu(IV) Sorption to Montmorillonite,” Environmental Science and Technology, DOI: 10.1021/es305257s.