> I am a student at Western Michigan University and I work in the Water Chemistry Lab for Dr. Michael Barcelona. I am trying to gain some proficiency with PHREEQC and I have a question for you. I'm using PHREEQC to model the interaction between ground water, sea water, and limestone aquifers. The trouble I'm having is that I can't seem to figure out how to have the limestone interact with the sea water and ground water. I have input the sea water and ground water with the command SOLUTION. I'm just not sure what to put the limestone under and then what to do to get the desired interaction. Do you have any insight to this problem? I would really appreciate your help. The following is what should happen in seawater mixing thermodynamically. You will notice that calcite dissolves and dolomite precipitates in the mixing zone, however, this does not happen in reality because of the slow kinetics of dolomite precipitation. David SOLUTION 1 SEAWATER FROM NORDSTROM ET AL. (1979) units ppm pH 8.22 pe 8.451 density 1.023 temp 25.0 redox O(0)/O(-2) Ca 412.3 Mg 1291.8 Na 10768.0 K 399.1 Si 4.28 Cl 19353.0 Alkalinity 141.682 as HCO3 S(6) 2712.0 O(0) 1.0 O2(g) -0.7 END SOLUTION 2 Pure water pH 7 END # Make carbonate ground water USE solution 2 EQUILIBRIUM_PHASES 2 Calcite 0 10 Dolomite 0 10 CO2(g) -2.0 10 SAVE solution 2 END # Mix G-W and Seawater, equilibrate with carbonates MIX 1 0.5 2 0.5 EQUILIBRIUM_PHASES 1 Calcite 0 10 Dolomite 0 10 END David Parkhurst (dlpark@xxxxxxxx) U.S. Geological Survey Box 25046, MS 413 Denver Federal Center Denver, CO 80225 Project web page: http://wwwbrr.cr.usgs.gov/projects/GWC_coupled
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