Reactive transport models of the properties of water-saturated porous media almost invariably assume that the aqueous geochemistry of confined water is identical to that of bulk liquid water. This assumption is challenged by evidence that confinement influences the stability of ice and the precipitation of minerals in water-filled nanopores. This pore-size dependence of aqueous geochemistry may impact the properties of natural nanoporous media that are ubiquitous in the subsurface, including clayey rocks (shales, mudstones) and hydrated silica gel coatings (on dissolving silicate minerals and glasses). Here, we present molecular dynamics (MD) simulations of clay and silica nanopores designed to determine the influence of confinement on the chemical potentials of salts (NaCl) and gaseous solutes (CO2, CH4, noble gases). Our simulations reveal the existence of a significant confinement effect and provide insight into the molecular scale basis of this effect.

Aqueous geochemistry of water confined in clay and silica nanopores

249th National Meeting (2015)

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Aqueous geochemistry of water confined in clay and silica nanopores<br />