Here's a file that should help. It adds CO2 to your solution until calcite is saturated. It also adds NaOH to maintain the pH at 10. If you add enough CO2 to get close to 1 atmosphere pCO2 (as it looks like you intended from your input file), you will have a very concentrated solution of NaHCO3 and the program could fail to converge. . In this run, it takes about 25 micromoles of CO2 to get to calcite saturation, but you need to add 100 micromoles of NaOH and log(pCO2) is -7. It helps to add the oxygen to define the redox condition more robustly. David SOLUTION 1 Nutrient Solution, pH 10, No CO2 temp 30 pH 10 pe 4 redox pe units umol/kgw density 1 B 0.16 Ca 700 Cl 256 charge K 133 Mg 133 Na 0 N(-3) 47 N(5) 423 P 3 Zn 0.1 Cu 0.04 Fe 5 Mn 0.2 S(6) 500 C 0.00001 -water 1 # kg EQUILIBRIUM_PHASES 1 # Fix pO2 at .1 atm O2(g) -1 # Add CO2(g) until calcite saturation Calcite 0.0 CO2(g) 10 # Add NaOH to pH 10 FIX_H+ -10. NaOH 10 PHASES # Fake phase used to fix pH FIX_H+ H+ = H+ logK 0 END David Parkhurst (dlpark@xxxxxxxx) U.S. Geological Survey Box 25046, MS 413 Denver Federal Center Denver, CO 80225
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