Fresh water calculations Dissolution of carbonate rocks by means of meteoric water (saturated by CO2) can be simulated by another program, not to be downloaded by now. It employs different parametrization for reactions, as those used in seawater cannot be used any longer. Ionic streght of rain water is very low indeed, therefore thermodynamic parameters as DH,  DS and  DG are employed, with their  variation with temperature, to calculate Keq. Here as follows the thermodynamic values and their temperature variations (pressure is alway 1 atm, as CaCO3 dissolution occurs only in surface waters) ' CO2 + H2O <==> H2CO3 deltaH1 = -699650 + 393518 + 285830 deltaG = deltaH1 - T0*(187.4 - 213.74 - 69.91) K1 = exp(-1*deltaG/(R*T0)) ' H2CO3 <==> H+ + HCO3- deltaH2 = -691990 + 699650 deltaG = deltaH2 - T0*(91.2 - 187.4) K2 = exp(-1*deltaG/(R*T0)) ' HCO3- <==> H+ + CO3-- deltaH3 = -677140 + 691990 deltaG = deltaH3 - T0*(-56.9 - 91.2) K3 = exp(-1*deltaG/(R*T0)) ' H2O <==> H+ + OH- deltaH4 = -229994 + 285830 deltaG = deltaH4 - T0*(-10.75 - 69.91) K4 = exp(-1*deltaG/(R*T0)) ' CaCO3calcite <==> Ca++ + CO3-- deltaH5 = -542830 -677140 + 1206920 deltaG = deltaH5 - T0*(-53.1 - 56.9 - 92.9) K5 = exp(-1*deltaG/(R*T0)) ' CaCO3aragonite <==> Ca++ + CO3-- deltaH6 = -542830 -677140 + 1207130 deltaG = deltaH6 - T0*(-53.1 - 56.9 - 88.7) K6 = exp(-1*deltaG/(R*T0)) ' Ca++ + OH- <==> CaOH+ deltaG = -7576 K7 = exp(-1*deltaG/(R*T0)) ' Mg++ + OH- <==> MgOH+ deltaG = -14656 K8 = exp(-1*deltaG/(R*T0))  The plots here displayed show what amount of CO2  that is releaded (outgassed) in the atmosphere and how much Ca++ ions are  dissolved in fresh water. Calculation assumes that water is saturated with CO2 and that CaCO3 is dissolved (mainly as calcium bicarbonate) until saturation is reached. In the first plot CO2 concentration varies from 280 to 780 ppm where T = 17°C is kept constant. Note that the amount of absorbed CO2 nearly equals Ca++ ions