Experimental and modelling study of plutonium uptake by suspended matter in aquatic environments from southern Spain.

Kinetic transfer coefficients are important parameters to understand and reliably model the behaviour of non-conservative radionuclides in aquatic environments. This report pertains to a series of five radiotracer experiments on Pu uptake in natural aqueous suspensions of unfiltered waters from three aquatic systems in the south of Spain (Gergal reservoir, the Guadalquivir river, and the estuary of the Tinto river). The experimental procedure ensured the simulation of environmental conditions. Pu activity was measured by a liquid scintillation technique. The uptake curves, covering a period up to one week, are discussed with respect to numerical uptake kinetics models. The data suggest that in our experimental setting the main pathways for Pu uptake consist of two parallel and reversible reactions followed by a consecutive non-reversible reaction. Kinetic transfer coefficients were estimated by a fitting procedure and a comparative study was followed.