Are artificial tracers conservative in argillaceous media ? The Tournemire claystone case.
S, Savoye, L. De Windt, C Beaucaire, G. Bruno, N. Guitard.
actes du congrès "WRI-10 Water-Rock Interaction , Vilasinius, Italie - 10/15 juin 2001" Cidu(ed.) p 1383-1386
Hydraulically active fractures have been recently discovered in indurated clays of the Tournemire site (Aveyron, France). The diffusion through the clay matrix would not be the only transport mechanism, due to the occurrence of this type of fractures. A tracer experiment is thus considered to estimate the extent of the circulation in such networks. In a first step, the sorption properties of the artificial tracers selected for the test (fluorescein, rhodamine WT, iodide and brormide) were investigated for calcite, which is the dominant fracture-filling mineral and for a non-altered bulk claystone sample. While rhodamine WT shows a sorptive behavior, particularly on the claystone fraction, fluorescein, iodide and bromide prove to be weakly sorbed on both calcite and claystone. However, the distribution coefficients obtained with iodide are not consistent with results from diffusion experiments, which questions the relationship between batch and diffusion experiments for halides.