Using in-situ radionuclides to model sediment transfer at the flow event time scale

P. Laguionie (1, 2) , Alain Crave (3) , P. Bonté (1, 2) , I. Lefèvre (1, 2)

1 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
2 GEDI - Géochimie Des Impacts
3 GR - Géosciences Rennes

Sediment flow modeling over geological time scales requires a good understanding of the sediment transport modes occurring in rivers. Mean sediment residence time within hydraulic networks in response to flow events needs to be determined. In this background, the fallout natural environment radionuclide beryllium-7 ($^7$Be, half-life of 53.3 days) and the in-situ artificial radionuclide iodine-131 ($^{131}$ I, half-life of 8.05 days) provide reliable tools to better understand the sediment transfer at the flow event time scale. Our model is based on the radioactive decay of the $^7$Be and $^{131}$I associated with suspended sediments. The short half-lives of $^7$Be and $^{131}$I allow phenomena to be studied at the flow event time scale. In this context radionuclide inputs have to be well-identified. The artificial iodine $^{131}$I source is well-defined as this radionuclide most likely originates from hospitals where it is used in radiotherapy. In the case of $^7$Be, the possibility that cities are radionuclide traps as they may provide high radionuclide concentration to channels, at time t, compared with bank inputs, is discussed. Natural environment radionuclide potentiality to estimate mean sediment residence time in a river section is demonstrated from in-situ data.

Mots clés: transfer model; sediments; in-situ radionuclides; short-time scales

Domaines: Sciences de l'environnement; Interfaces continentales, environnement; Géomorphologie; Hydrologie

P. Laguionie, Alain Crave, P. Bonté, I. Lefèvre. Using in-situ radionuclides to model sediment transfer at the flow event time scale. WIT Transactions on Ecology and the Environment, 2006, 90, pp.119-128. ⟨10.2495/DEB060121⟩. ⟨cea-02659561⟩