A radioecological water quality model including a multi-class sedimentary Dynamics approach. Presentation and comparison with a global approach.

O. El Ganaoui, F. Anselmet and P. Boyer Actes du congrès ECORAD, 3-7 sept 2001, Aix en Provence, France Radioprotection - Colloques, volume 37, C1-709/ C1-715.

The assessment of the radionuclides transfers in the physical components of rivers (water, suspended sediments bottom sediments) involves three disciplines: hydraulics, sedimentary dynamics and radioecology. In freshwater radioecological quality models, the radioecology is linked to the sedimentary dynamics through the adsorption / desorption process and the deposition / erosion fluxes. The assessment of these fluxes requires in situ and laboratory experiments to determine their relating parameters (settling velocity, critical shear stress of deposition and erosion, etc.). The models do not usually distinguish the different mineral particle classes and make the assumption that deposition and erosion processes cannot occur simultaneously. However, natural water flow is characterized by a wide and continuous range of different mineral particle classes. As a consequence, the assumed threshold between deposition and erosion is reduced. For example, the deposition of one class can come along with the erosion of another class. In this context, we present a radioecological model which includes a multi-class sedimentary dynamics model. To show the difference between this approach and a global one (obtained for a single average class of matter), a comparison between these two approaches concludes this paper.