The pressure of CO 2 or water in equilibrium with air is 3.2 x 10 -4 . The CO 2 pressure is changed in soils by microbial respiration and decaying organic matter. Pressure of CO 2 in soils may be as high as 1 x 10 -2 . Such systems are generally close to equilibrium with calcite or dolomite, or a combination of the two. The final calcium and magnesium concentrations are dictated by CO 2 pressure in the soil.
Lets examine the effect of pH on the calcium carbonate systems.
3 2- at these pH values.