SURFACE_MASTER_SPECIES
        Surf    SurfOH
SURFACE_SPECIES
        SurfOH = SurfOH
                log_k   0.0
        SurfOH  + H+ = SurfOH2+
                log_k   7.29
        SurfOH = SurfO- + H+
                log_k   -8.93
#       SurfOH + H3AsO3 = SurfH2AsO3 + H2O
#               log_k   5.41
        SurfOH + AsO4-3 + 3H+ = SurfH2AsO4 + H2O
                log_k   29.31
        SurfOH + AsO4-3 + 2H+ = SurfHAsO4- + H2O
                log_k   23.51
        SurfOH + AsO4-3 = SurfOHAsO4-3
                log_k   9.58
SOLUTION_MASTER_SPECIES
        As       H3AsO4        -1.0     74.9216         74.9216
SOLUTION_SPECIES
        H2O + 0.01e- = H2O.99
        log_k   -10
        -no_check
#H3AsO4 primary master species
        H3AsO4 = H3AsO4
        log_k           0.0
#H2AsO4-             482
        H3AsO4 = H2AsO4- + H+ 
        log_k           -2.243
        delta_h -1.69 kcal
#HAsO4-2             483
        H3AsO4 = HAsO4-2 + 2H+ 
        log_k           -9.001
        delta_h -0.92 kcal
#AsO4-3              484
        H3AsO4 = AsO4-3 + 3H+
        log_k           -20.597
        delta_h 3.43 kcal
SOLUTION 1 20 x precipitation
        pH      4.6
        pe      4.0     O2(g)   -0.7
        temp    25.
        units   mmol/kgw
        Ca      .191625
        Mg      .035797
        Na      .122668
        Cl      .133704
        C       .01096
        S       .235153         charge
END
USE solution 1
EQUILIBRIUM_PHASES 1
        Dolomite        0.0     2.7
        Calcite         0.0     1.0
        CO2(g)          -1.5    100.
SAVE solution 1
END
SOLUTION 2 Brine
        pH      5.713
        pe      4.0     O2(g)   -0.7
        temp    25.
        units   mol/kgw
        Ca      .4655
        Mg      .1609
        Na      5.402
        Cl      6.642           charge
        C       .00396
        S       .004725
        As      .01 umol/kgw
END
USE solution 2
EQUILIBRIUM_PHASES 2
        Dolomite        0.0     2.7
        Calcite         0.0     1.0
SAVE solution 2
END
EXCHANGE 2
        -equil with solution 2
        X       0.4
SURFACE 2
        -equil solution 2
        SurfOH          0.14     600.    30.
END
SELECTED_OUTPUT
        -file ok.sel
        -reset false
        -pH
USER_PUNCH
# Prints concentrations in mg/kgw to ok.sel
-heading        Ca      Mg      Na      Cl      C(4)    SO4     As
10 PUNCH TOT("Ca")*1e3*40.08
20 PUNCH TOT("Mg")*1e3*24.312
30 PUNCH TOT("Na")*1e3*23.
40 PUNCH TOT("Cl")*1e3*35.45
50 PUNCH TOT("C(4)")*1e3*61.   # as HCO3-
60 PUNCH TOT("S(6)")*1e3*96.   # as SO4
70 PUNCH TOT("As")*1e6*74.296  # ug/L
END