Surface complexation modelling of plutonium adsorption on sediments of the Esk estuary, Cumbria

Previous work has shown that plutonium is remobilised from Esk sediments at low salinities of overlying water. A constant capacitance surface complexation model has been developed in order to understand and model the chemical processes occurring. The model is based on detailed chemical characterisation of sediment samples from the estuary. The following measurements were carried out to provide input parameters for the model: specific surface area; total surface sites (by tritium exchange); proton and major ion exchange (by potentiometric titration); and plutonium partition coefficient (Kd) as a function of pH and salinity (by α spectrometry). A chemical model for the plutonium adsorption process has been developed. (Author)