In situ characterization of the Callovo-Oxfordian pore water composition

Up to 2005, knowledge on the Callovo-Oxfordian pore water composition was mainly built on geochemical modeling. A predictive geochemical model had been defined from physico-chemical and mineralogical properties obtained on rock samples. Since then, pore water characteristics have been obtained in situ at five depths between −430 and −505 m with three experimental set-ups. The first one based on water equilibration, the second one combining gas circulation and water sampling, and the third one originally devoted to hydrogeological measurements. These results show an overall convergence of the measured water compositions independently of the experimental concepts and of the sampling depths. Observed and calculated ionic concentrations differ by less than a factor of three for the major species, except for potassium and strontium. The experimental data yielded by this study will help to improve the geochemical modeling.