Dynamic Inhibition of Calcite Dissolution in Flowing Acidic Pb Solutions.

Reactions of mineral surfaces with dissolved metal ions at far-from-equilibrium conditions can deviate significantly from those in near-equilibrium systems due to steep concentration gradients, ion-surface interactions, and reactant transport effects that can lead to emergent behavior. We explored the effect of dissolved Pb on the dissolution rate and topographic evolution of calcite (104) surfaces under far-from-equilibrium acidic conditions (pH 3.7) in a confined single-pass laminar-flow geometry. Operando measurements by digital holographic microscopy were conducted over a range of Pb concentrations ([Pb] = 0 to 5 × 10 M) and flow velocities ( = 1.67-53.3 mm s). Calcite (104) surface dissolution rates decreased with increasing [Pb]. The inhibition of dissolution and the emergence of unique topographic features, including micropyramids, variable etch pit shapes, and larger scale topographic patterns, became increasingly apparent at [Pb] ≥ 5 × 10 M. A better understanding of such dynamic reactivity could be crucial for constructing accurate models of geochemical transport in aqueous carbonate systems.