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A surface complexation model for the chemical structure and reactivity of the carbonatewater interface is presented. The model postulates the formation of the hydration species >CO₃H⁰ and >MeOH⁰ at the surface of a divalent metal carbonate MeCO₃ (Me = Ca, Mn, Fe, etc.). The existence of these primary hydration species is supported by spectroscopic data. The following reactions are proposed to govern surface speciation in the MeCO₃(s)-H₂O-CO₂ system: CO₃H⁰a2>CO₃⁻ + H⁺(1) CO₃H⁰ + Me²⁺a2>CO₃Me⁺ + H⁺(2) MeOH₂⁺a2 >MeOH⁰ + H⁺(3) MeOH⁰a2 >MeO⁻ + H⁺(4) MeOH⁰ + CO₂a2 >MeHCO₃^o (5) MeOH⁰ + CO₂a2 >MeCO₃⁻+ H⁺(6) It is shown in this paper that the surface complexation model provides a systematic explanation of surface charge development and dissolution kinetics of carbonate minerals. The intrinsic stability constants of the surface complexation reactions agree well with the …