Determination of pore water composition and species-specific transport parameters by a new method using laboratory core infiltration: examples from opalinus clay (Mont Terri) and Callovo-Oxfordian clay (Bure)

The quantification of transport and water-rock interaction and its rates in very low permeability rocks such as clay-stone are used to interpret gradients across formations in isotopic, chemical, and gas composition that have evolved over thousands to millions of years. This quantitative understanding allows evaluation of a clay formation as a barrier for deep disposal of radioactive waste. Difficulties in sampling pore water from clay-stone are due to very low hydraulic conductivities (∼ 10-13 m/s), the presence of reactive components such as pyrite, carbonate, organics, and in-gassing or degassing of CO2 during sampling. The aim of our new method is to minimize artifacts and to obtain both chemical and transport information from a single experiment. (authors)