Isotopic disequilibrium during uptake of atmospheric CO(2) into mine process waters: Implications for CO(2) sequestration

Dypingite, a hydrated Mg-carbonate mineral, was precipitated from high-pH, high salinity solutions to investigate controls on carbon fixation and to identify the isotopic characteristics of mineral sequestration in mine tailings. delta(13)C values of dissolved inorganic carbon content and synthetic dypingite are significantly more negative than those predicted for equilibrium exchange of CO(2) gas between the atmosphere and solution. The measured delta(13)C of aqueous carbonate species is consistent with a kinetic fractionation that results from a slow diffusion of atmospheric CO(2) into solution. During dypingite precipitation, dissolved inorganic carbon concentrations decrease and delta(13)C values become more negative, indicating that the rate of CO(2) uptake into solution was outpaced by the rate of carbon fixation within the precipitate.