Equilibrium Partial Pressure of CO2 in the Callovo-Oxfordian Argillite as a Function of Relative Humidity.

Arnault Lassin (1, 2) , Nicolas C.M. Marty (1) , Benoît Henry (1) , Joachim Tremosa (1) , Hélène Gailhanou (1) , Scott Altman (3) , Eric C. Gaucher (1)

1 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)
2 ISTO - Institut des Sciences de la Terre d'Orléans - UMR7327
3 ANDRA - Agence Nationale pour la Gestion des Déchets Radioactifs

Understanding the behavior of a clay mineral-rich rock submitted to different physical-chemical perturbations is important for assessing the safety of nuclear waste disposal facilities in the corresponding geological formations. In this work we studied the effect of rock desaturation on the CO2 partial pressure signature of the Callovo-Oxfordian argillite. This integrated study, which combines experiments and geochemical modeling, points out the primary role of capillary forces on the chemical equilibria. In particular, it was possible to model, without any fitting parameters, the experimental decrease of pCO2 as a function of decreasing water content in the argillite. Moreover, this application to a complex natural system is an example of confirmation of the theoretical concepts of geochemistry in capillary contexts and is promising for dealing with other natural and industrial systems.

Keywords: Nuclear waste storage; Callovo-Oxfordian argilite; Capillary systems; Relative humidity; Isobar/anisobar contexts; Carbon dioxide; Geochemical modeling

Domains: Continental interfaces, environment; Global Changes

Arnault Lassin, Nicolas C.M. Marty, Benoît Henry, Joachim Tremosa, Hélène Gailhanou, et al.. Equilibrium Partial Pressure of CO2 in the Callovo-Oxfordian Argillite as a Function of Relative Humidity.. Procedia Earth and Planetary Science, 2013, 7, pp.459-462. ⟨10.1016/j.proeps.2013.03.083⟩. ⟨insu-00825201⟩