Calcite solubility, effect complexing

It is useful to construct a graph relating carbonate mineral solubilities to CO2 pressure. This can be done for calcite starting with equilibrium constant expression (6.2) above. If done rigorously, the derivation accounts for the effects of ion activity coefficients and the presence of CaHCOI and CaCOf ion pairs and of CaOH. Considering all complexation, the exact charge-balance equation for a pure water in which calcite is dissolving is... 

The effect of DOM on calcium solubility is less apparent than expected. Calcite precipitates, as in the absence of DOM (Figure AS.4), from a calcium concentration of 3 mM, as shown in Figure A5.8. However, the calcite concentration is now varied with a concentration of 0,12 at 3 mM and 2,12 at 5 mM. The calcite concentration is reduced by the concentration of the Ca-DOM complex (see Figure A5.9). 

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