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Example 1.-- Speciation Calculation

This example calculates the distribution of aqueous species in seawater and the saturation state of seawater relative to a set of minerals. To demonstrate how to expand the model to new elements, uranium is added to the aqueous model defined by phreeqc.dat . [One of the database files included with the program distribution, wateq4f.dat , is derived from WATEQ4F (Ball and Nordstrom, 1991) and includes uranium.]

Table 10. --Seawater composition

[Concentration is in parts per million (ppm) unless specified otherwise]

Analysis

PHREEQC
notation

Concentration

Calcium

Ca

412.3

Magnesium

Mg

1291.8

Sodium

Na

10768.0

Potassium

K

399.1

Iron

Fe

.002

Manganese

Mn

.0002

Silica, as SiO 2

Si

4.28

Chloride

Cl

19353.0

Alkalinity, as HCO 3 -

Alkalinity

141.682

Sulfate, as SO 4 2-

S(6)

2712.0

Nitrate. as NO 3 -

N(5)

.29

Ammonium, as NH 4 +

N(-3)

.03

Uranium

U

.0033

pH, standard units

pH

8.22

pe, unitless

pe

8.451

Temperature, o C

temperature

25.0

Density, kilograms per liter

density

1.023

The essential data needed for a speciation calculation are the temperature, pH, and concentrations of elements and (or) element valence states. These data for seawater are given in table 10. The input data set for this example calculation is shown in table 11. A comment about the calculations performed in this simulation is included with the TITLE keyword. The SOLUTION data block defines the composition of seawater. Note that valence states are identified by the chemical symbol for the element followed by the valence in parentheses [S(6), N(5), N(-3), and O(0)].

The pe to be used for distributing redox elements and for calculating saturation indices is specified by the redox identifier. In this example, a pe is to be calculated from the O(-2)/O(0) redox couple, which corresponds to the dissolved oxygen/water couple, and this calculated pe will be used for all calculations that require a pe. If redox were not specified, the default would be the input pe. The default redox identifier can be overridden for any redox element, as demonstrated by the manganese input, where the input pe will be used to speciate manganese among its valence states, and the uranium input, where the nitrate/ammonium couple will be used to calculate a pe with which to speciate uranium among its valence states.

The default units are specified to be ppm in this data set ( units identifier). This default can be overridden for any concentration, as demonstrated by the uranium concentration, which is specified to be ppb instead of ppm. Because ppm is a mass unit, not a mole unit, the program must use a gram formula weight to convert each concentration into molal units. The default gram formula weights for each master species are specified in the SOLUTION_MASTER_SPECIES input (the values for the default database phreeqc.dat are listed in table 4 and in Attachment B). If the data are reported relative to a gram formula weight different from the default, it is necessary to specify the appropriate gram formula weight in the input data set. This can be done with the gfw identifier, where the actual gram formula weight is input--the gram-formula weight by which to convert nitrate is specified to be 62.0 g/mol, or more simply with the as identifier, where the chemical formula for the reported units is input, as shown in the input for alkalinity and ammonium in this example. Note finally that the concentration of O(0), dissolved oxygen, is given an initial estimate of 1 ppm, but that its concentration will be adjusted until a log partial pressure of oxygen gas of -0.7 is achieved. [O2(g) is defined under PHASES input of the default database file (Attachment B).] When using phase equilibria to specify initial concentrations [like O(0) in this example], only one concentration is adjusted. For example, if gypsum were used to adjust the calcium concentration, the concentration of calcium would vary, but the concentration of sulfate would remain fixed.

Table 11. --Input data set for example 1

TITLE Example 1.--Add uranium and speciate seawater.
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
        Fe              0.002
        Mn              0.0002  pe
        Si              4.28
        Cl              19353.0
        Alkalinity      141.682 as HCO3
        S(6)            2712.0
        N(5)            0.29    gfw   62.0
        N(-3)           0.03    as    NH4
        U               3.3     ppb   N(5)/N(-3)
        O(0)            1.0     O2(g) -0.7
SOLUTION_MASTER_SPECIES
        U       U+4     0.0     238.0290     238.0290
        U(4)    U+4     0.0     238.0290
        U(5)    UO2+    0.0     238.0290
        U(6)    UO2+2   0.0     238.0290
SOLUTION_SPECIES
        #primary master species for U
        #is also secondary master species for U(4)
        U+4 = U+4
                log_k          0.0
        U+4 + 4 H2O = U(OH)4 + 4 H+
                log_k          -8.538
                delta_h        24.760 kcal
        U+4 + 5 H2O = U(OH)5- + 5 H+
                log_k          -13.147
                delta_h        27.580 kcal
        #secondary master species for U(5)
        U+4 + 2 H2O = UO2+ + 4 H+ + e-
                log_k          -6.432
                delta_h        31.130 kcal
        #secondary master species for U(6)
        U+4 + 2 H2O = UO2+2 + 4 H+ + 2 e-
                log_k          -9.217
                delta_h        34.430 kcal
        UO2+2 + H2O = UO2OH+ + H+
                log_k          -5.782
                delta_h        11.015 kcal
        2UO2+2 + 2H2O = (UO2)2(OH)2+2 + 2H+
                log_k          -5.626
                delta_h        -36.04 kcal
        3UO2+2 + 5H2O = (UO2)3(OH)5+ + 5H+
                log_k          -15.641
                delta_h        -44.27 kcal
        UO2+2 + CO3-2 = UO2CO3
                log_k          10.064
                delta_h        0.84 kcal
        UO2+2 + 2CO3-2 = UO2(CO3)2-2
                log_k          16.977
                delta_h        3.48 kcal
        UO2+2 + 3CO3-2 = UO2(CO3)3-4
                log_k          21.397
                delta_h        -8.78 kcal
PHASES
        Uraninite
        UO2 + 4 H+ = U+4 + 2 H2O
        log_k          -3.490
        delta_h        -18.630 kcal
END
 

Uranium is not included in phreeqc.dat , one of the database files that is distributed with the program. Thus, data to describe the thermodynamics and composition of aqueous uranium species must be included in the input data when using this database file. Two keyword data blocks are needed to define the uranium species, SOLUTION_MASTER_SPECIES and SOLUTION_SPECIES. By adding these two data blocks to the input data file, aqueous uranium species will be defined for the duration of the run. To add uranium permanently to the list of elements, these data blocks should be added to the database file. The data for uranium shown here are intended to be illustrative and are not a complete description of uranium speciation.

It is necessary to define a primary master species for uranium with SOLUTION_MASTER_SPECIES input. Because uranium is a redox-active element, it is also necessary to define a secondary master species for each valence state of uranium. The data block SOLUTION_MASTER_SPECIES (table 11) defines U +4 as the primary master species for uranium and also as the secondary master species for the +4 valence state. UO 2 + is the secondary master species for the +5 valence state, and UO 2 +2 is the secondary master species for the +6 valence state. Equations defining these aqueous species plus any other complexes of uranium must be defined through SOLUTION_SPECIES input.

In the data block SOLUTION_SPECIES (table 11), the primary and secondary master species are noted with comments. A primary master species is always defined in the form of an identity reaction (U+4 = U+4). Secondary master species are the only aqueous species that contain electrons in their chemical reaction. Additional hydroxide and carbonate complexes are defined for the +4 and +6 valence states, but none for the +5 state.

Finally, a new phase, uraninite, is defined with PHASES input. This phase will be used in calculating saturation indices in speciation modeling, but could also be used, without redefinition, for batch-reaction, transport, or inverse calculations within the computer run.

Table 12. --Output for example 1

   Input file: ex1
  Output file: ex1.out
Database file: ../phreeqc.dat
 
------------------
Reading data base.
------------------
 
        SOLUTION_MASTER_SPECIES
        SOLUTION_SPECIES
        PHASES
        EXCHANGE_MASTER_SPECIES
        EXCHANGE_SPECIES
        SURFACE_MASTER_SPECIES
        SURFACE_SPECIES
        RATES
        END
------------------------------------
Reading input data for simulation 1.
------------------------------------
 
        TITLE Example 1.--Add uranium and speciate seawater.
        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
                Fe              0.002
                Mn              0.0002  pe
                Si              4.28
                Cl              19353.0
                Alkalinity      141.682 as HCO3
                S(6)            2712.0
                N(5)            0.29    gfw   62.0
                N(-3)           0.03    as    NH4
                U               3.3     ppb   N(5)/N(-3)
                O(0)            1.0     O2(g) -0.7
        SOLUTION_MASTER_SPECIES
                U       U+4     0.0     238.0290     238.0290
                U(4)    U+4     0.0     238.0290
                U(5)    UO2+    0.0     238.0290
                U(6)    UO2+2   0.0     238.0290
        SOLUTION_SPECIES
                U+4 = U+4
                        log_k          0.0
                U+4 + 4 H2O = U(OH)4 + 4 H+
                        log_k          -8.538
                        delta_h        24.760 kcal
                U+4 + 5 H2O = U(OH)5- + 5 H+
                        log_k          -13.147
                        delta_h        27.580 kcal
                U+4 + 2 H2O = UO2+ + 4 H+ + e-
                        log_k          -6.432
                        delta_h        31.130 kcal
                U+4 + 2 H2O = UO2+2 + 4 H+ + 2 e-
                        log_k          -9.217
                        delta_h        34.430 kcal
                UO2+2 + H2O = UO2OH+ + H+
                        log_k          -5.782
                        delta_h        11.015 kcal
                2UO2+2 + 2H2O = (UO2)2(OH)2+2 + 2H+
                        log_k          -5.626
                        delta_h        -36.04 kcal
                3UO2+2 + 5H2O = (UO2)3(OH)5+ + 5H+
                        log_k          -15.641
                        delta_h        -44.27 kcal
                UO2+2 + CO3-2 = UO2CO3
                        log_k          10.064
                        delta_h        0.84 kcal
                UO2+2 + 2CO3-2 = UO2(CO3)2-2
                        log_k          16.977
                        delta_h        3.48 kcal
                UO2+2 + 3CO3-2 = UO2(CO3)3-4
                        log_k          21.397
                        delta_h        -8.78 kcal
        PHASES
                Uraninite
                UO2 + 4 H+ = U+4 + 2 H2O
                log_k          -3.490
                delta_h        -18.630 kcal
        END
-----
TITLE
-----
 
 Example 1.--Add uranium and speciate seawater.
 
-------------------------------------------
Beginning of initial solution calculations.
-------------------------------------------
 
Initial solution 1.     SEAWATER FROM NORDSTROM ET AL. (1979)
 
-----------------------------Solution composition------------------------------
 
        Elements           Molality       Moles
 
        Alkalinity        2.406e-03   2.406e-03
        Ca                1.066e-02   1.066e-02
        Cl                5.657e-01   5.657e-01
        Fe                3.711e-08   3.711e-08
        K                 1.058e-02   1.058e-02
        Mg                5.507e-02   5.507e-02
        Mn                3.773e-09   3.773e-09
        N(-3)             1.724e-06   1.724e-06
        N(5)              4.847e-06   4.847e-06
        Na                4.854e-01   4.854e-01
        O(0)              3.746e-04   3.746e-04  Equilibrium with O2(g)
        S(6)              2.926e-02   2.926e-02
        Si                7.382e-05   7.382e-05
        U                 1.437e-08   1.437e-08
 
----------------------------Description of solution----------------------------
 
                                       pH  =   8.220    
                                       pe  =   8.451    
                        Activity of water  =   0.981
                           Ionic strength  =   6.748e-01
                       Mass of water (kg)  =   1.000e+00
                    Total carbon (mol/kg)  =   2.180e-03
                       Total CO2 (mol/kg)  =   2.180e-03
                      Temperature (deg C)  =  25.000
                  Electrical balance (eq)  =   7.936e-04
 Percent error, 100*(Cat-|An|)/(Cat+|An|)  =   0.07
                               Iterations  =   7
                                  Total H  = 1.110147e+02
                                  Total O  = 5.563047e+01
 
---------------------------------Redox couples---------------------------------
 
        Redox couple             pe  Eh (volts)
 
        N(-3)/N(5)           4.6750      0.2766
        O(-2)/O(0)          12.3893      0.7329
 
----------------------------Distribution of species----------------------------
 
                                                   Log       Log         Log 
        Species            Molality    Activity  Molality  Activity     Gamma
 
        OH-               2.674e-06   1.629e-06    -5.573    -5.788    -0.215
        H+                7.981e-09   6.026e-09    -8.098    -8.220    -0.122
        H2O               5.551e+01   9.806e-01    -0.009    -0.009     0.000
C(4)             2.180e-03
        HCO3-             1.514e-03   1.023e-03    -2.820    -2.990    -0.170
        MgHCO3+           2.195e-04   1.640e-04    -3.658    -3.785    -0.127
        NaHCO3            1.667e-04   1.948e-04    -3.778    -3.710     0.067
        MgCO3             8.913e-05   1.041e-04    -4.050    -3.982     0.067
        NaCO3-            6.718e-05   5.020e-05    -4.173    -4.299    -0.127
        CaHCO3+           4.597e-05   3.106e-05    -4.337    -4.508    -0.170
        CO3-2             3.821e-05   7.959e-06    -4.418    -5.099    -0.681
        CaCO3             2.725e-05   3.183e-05    -4.565    -4.497     0.067
        CO2               1.210e-05   1.413e-05    -4.917    -4.850     0.067
        UO2(CO3)3-4       1.255e-08   1.184e-10    -7.901    -9.927    -2.025
        UO2(CO3)2-2       1.814e-09   5.653e-10    -8.741    -9.248    -0.506
        MnCO3             2.696e-10   3.150e-10    -9.569    -9.502     0.067
        MnHCO3+           6.077e-11   4.541e-11   -10.216   -10.343    -0.127
        UO2CO3            7.429e-12   8.678e-12   -11.129   -11.062     0.067
        FeCO3             1.952e-20   2.281e-20   -19.709   -19.642     0.067
        FeHCO3+           1.635e-20   1.222e-20   -19.786   -19.913    -0.127
Ca               1.066e-02
        Ca+2              9.504e-03   2.380e-03    -2.022    -2.623    -0.601
        CaSO4             1.083e-03   1.266e-03    -2.965    -2.898     0.067
        CaHCO3+           4.597e-05   3.106e-05    -4.337    -4.508    -0.170
        CaCO3             2.725e-05   3.183e-05    -4.565    -4.497     0.067
        CaOH+             8.604e-08   6.429e-08    -7.065    -7.192    -0.127
        CaHSO4+           5.979e-11   4.467e-11   -10.223   -10.350    -0.127
Cl               5.657e-01
        Cl-               5.657e-01   3.528e-01    -0.247    -0.452    -0.205
        MnCl+             9.582e-10   7.160e-10    -9.019    -9.145    -0.127
        MnCl2             9.439e-11   1.103e-10   -10.025    -9.958     0.067
        MnCl3-            1.434e-11   1.071e-11   -10.844   -10.970    -0.127
        FeCl+2            9.557e-19   2.978e-19   -18.020   -18.526    -0.506
        FeCl2+            6.281e-19   4.693e-19   -18.202   -18.329    -0.127
        FeCl+             7.786e-20   5.817e-20   -19.109   -19.235    -0.127
        FeCl3             1.417e-20   1.656e-20   -19.849   -19.781     0.067
Fe(2)            6.909e-19
        Fe+2              5.205e-19   1.195e-19   -18.284   -18.923    -0.639
        FeCl+             7.786e-20   5.817e-20   -19.109   -19.235    -0.127
        FeSO4             4.845e-20   5.660e-20   -19.315   -19.247     0.067
        FeCO3             1.952e-20   2.281e-20   -19.709   -19.642     0.067
        FeHCO3+           1.635e-20   1.222e-20   -19.786   -19.913    -0.127
        FeOH+             8.227e-21   6.147e-21   -20.085   -20.211    -0.127
        FeHSO4+           3.000e-27   2.242e-27   -26.523   -26.649    -0.127
Fe(3)            3.711e-08
        Fe(OH)3           2.841e-08   3.318e-08    -7.547    -7.479     0.067
        Fe(OH)4-          6.591e-09   4.924e-09    -8.181    -8.308    -0.127
        Fe(OH)2+          2.118e-09   1.583e-09    -8.674    -8.801    -0.127
        FeOH+2            9.425e-14   2.937e-14   -13.026   -13.532    -0.506
        FeSO4+            1.093e-18   8.167e-19   -17.961   -18.088    -0.127
        FeCl+2            9.557e-19   2.978e-19   -18.020   -18.526    -0.506
        FeCl2+            6.281e-19   4.693e-19   -18.202   -18.329    -0.127
        Fe+3              3.509e-19   2.796e-20   -18.455   -19.554    -1.099
        Fe(SO4)2-         6.372e-20   4.761e-20   -19.196   -19.322    -0.127
        FeCl3             1.417e-20   1.656e-20   -19.849   -19.781     0.067
        Fe2(OH)2+4        2.462e-24   2.322e-26   -23.609   -25.634    -2.025
        FeHSO4+2          4.228e-26   1.318e-26   -25.374   -25.880    -0.506
        Fe3(OH)4+5        1.122e-29   7.679e-33   -28.950   -32.115    -3.165
H(0)             0.000e+00
        H2                0.000e+00   0.000e+00   -44.436   -44.369     0.067
K                1.058e-02
        K+                1.042e-02   6.495e-03    -1.982    -2.187    -0.205
        KSO4-             1.627e-04   1.216e-04    -3.789    -3.915    -0.127
        KOH               3.137e-09   3.665e-09    -8.503    -8.436     0.067
Mg               5.507e-02
        Mg+2              4.742e-02   1.371e-02    -1.324    -1.863    -0.539
        MgSO4             7.330e-03   8.562e-03    -2.135    -2.067     0.067
        MgHCO3+           2.195e-04   1.640e-04    -3.658    -3.785    -0.127
        MgCO3             8.913e-05   1.041e-04    -4.050    -3.982     0.067
        MgOH+             1.084e-05   8.100e-06    -4.965    -5.092    -0.127
Mn(2)            3.773e-09
        Mn+2              2.171e-09   4.982e-10    -8.663    -9.303    -0.639
        MnCl+             9.582e-10   7.160e-10    -9.019    -9.145    -0.127
        MnCO3             2.696e-10   3.150e-10    -9.569    -9.502     0.067
        MnSO4             2.021e-10   2.360e-10    -9.695    -9.627     0.067
        MnCl2             9.439e-11   1.103e-10   -10.025    -9.958     0.067
        MnHCO3+           6.077e-11   4.541e-11   -10.216   -10.343    -0.127
        MnCl3-            1.434e-11   1.071e-11   -10.844   -10.970    -0.127
        MnOH+             2.789e-12   2.084e-12   -11.555   -11.681    -0.127
        Mn(NO3)2          1.375e-20   1.606e-20   -19.862   -19.794     0.067
Mn(3)            5.993e-26
        Mn+3              5.993e-26   4.349e-27   -25.222   -26.362    -1.139
N(-3)            1.724e-06
        NH4+              1.609e-06   9.049e-07    -5.794    -6.043    -0.250
        NH3               7.326e-08   8.558e-08    -7.135    -7.068     0.067
        NH4SO4-           4.157e-08   3.106e-08    -7.381    -7.508    -0.127
N(5)             4.847e-06
        NO3-              4.847e-06   2.846e-06    -5.315    -5.546    -0.231
        Mn(NO3)2          1.375e-20   1.606e-20   -19.862   -19.794     0.067
Na               4.854e-01
        Na+               4.791e-01   3.387e-01    -0.320    -0.470    -0.151
        NaSO4-            6.053e-03   4.523e-03    -2.218    -2.345    -0.127
        NaHCO3            1.667e-04   1.948e-04    -3.778    -3.710     0.067
        NaCO3-            6.718e-05   5.020e-05    -4.173    -4.299    -0.127
        NaOH              3.117e-07   3.641e-07    -6.506    -6.439     0.067
O(0)             3.746e-04
        O2                1.873e-04   2.188e-04    -3.727    -3.660     0.067
S(6)             2.926e-02
        SO4-2             1.463e-02   2.664e-03    -1.835    -2.574    -0.740
        MgSO4             7.330e-03   8.562e-03    -2.135    -2.067     0.067
        NaSO4-            6.053e-03   4.523e-03    -2.218    -2.345    -0.127
        CaSO4             1.083e-03   1.266e-03    -2.965    -2.898     0.067
        KSO4-             1.627e-04   1.216e-04    -3.789    -3.915    -0.127
        NH4SO4-           4.157e-08   3.106e-08    -7.381    -7.508    -0.127
        HSO4-             2.089e-09   1.561e-09    -8.680    -8.807    -0.127
        MnSO4             2.021e-10   2.360e-10    -9.695    -9.627     0.067
        CaHSO4+           5.979e-11   4.467e-11   -10.223   -10.350    -0.127
        FeSO4+            1.093e-18   8.167e-19   -17.961   -18.088    -0.127
        Fe(SO4)2-         6.372e-20   4.761e-20   -19.196   -19.322    -0.127
        FeSO4             4.845e-20   5.660e-20   -19.315   -19.247     0.067
        FeHSO4+2          4.228e-26   1.318e-26   -25.374   -25.880    -0.506
        FeHSO4+           3.000e-27   2.242e-27   -26.523   -26.649    -0.127
Si               7.382e-05
        H4SiO4            7.110e-05   8.306e-05    -4.148    -4.081     0.067
        H3SiO4-           2.720e-06   2.032e-06    -5.565    -5.692    -0.127
        H2SiO4-2          7.362e-11   2.294e-11   -10.133   -10.639    -0.506
U(4)             1.034e-21
        U(OH)5-           1.034e-21   7.726e-22   -20.985   -21.112    -0.127
        U(OH)4            1.652e-25   1.930e-25   -24.782   -24.715     0.067
        U+4               0.000e+00   0.000e+00   -46.997   -49.022    -2.025
U(5)             1.622e-18
        UO2+              1.622e-18   1.212e-18   -17.790   -17.916    -0.127
U(6)             1.437e-08
        UO2(CO3)3-4       1.255e-08   1.184e-10    -7.901    -9.927    -2.025
        UO2(CO3)2-2       1.814e-09   5.653e-10    -8.741    -9.248    -0.506
        UO2CO3            7.429e-12   8.678e-12   -11.129   -11.062     0.067
        UO2OH+            3.385e-14   2.530e-14   -13.470   -13.597    -0.127
        UO2+2             3.019e-16   9.409e-17   -15.520   -16.026    -0.506
        (UO2)2(OH)2+2     1.780e-21   5.547e-22   -20.750   -21.256    -0.506
        (UO2)3(OH)5+      2.908e-23   2.173e-23   -22.536   -22.663    -0.127
 
------------------------------Saturation indices-------------------------------
 
        Phase               SI log IAP  log KT
 
        Anhydrite        -0.84   -5.20   -4.36  CaSO4
        Aragonite         0.61   -7.72   -8.34  CaCO3
        Calcite           0.76   -7.72   -8.48  CaCO3
        Chalcedony       -0.51   -4.06   -3.55  SiO2
        Chrysotile        3.36   35.56   32.20  Mg3Si2O5(OH)4
        CO2(g)           -3.38  -21.53  -18.15  CO2
        Dolomite          2.41  -14.68  -17.09  CaMg(CO3)2
        Fe(OH)3(a)        0.19   -3.42   -3.61  Fe(OH)3
        Goethite          6.09   -3.41   -9.50  FeOOH
        Gypsum           -0.63   -5.21   -4.58  CaSO4:2H2O
        H2(g)           -41.22    1.82   43.04  H2
        H2O(g)           -1.52   -0.01    1.51  H2O
        Halite           -2.50   -0.92    1.58  NaCl
        Hausmannite       1.57   19.56   17.99  Mn3O4
        Hematite         14.20   -6.81  -21.01  Fe2O3
        Jarosite-K       -7.52  -42.23  -34.71  KFe3(SO4)2(OH)6
        Manganite         2.39    6.21    3.82  MnOOH
        Melanterite     -19.35  -21.56   -2.21  FeSO4:7H2O
        NH3(g)           -8.84    2.18   11.01  NH3
        O2(g)            -0.70   -3.66   -2.96  O2
        Pyrochroite      -8.08    7.12   15.20  Mn(OH)2
        Pyrolusite        6.96    5.30   -1.66  MnO2
        Quartz           -0.08   -4.06   -3.98  SiO2
        Rhodochrosite    -3.27  -14.40  -11.13  MnCO3
        Sepiolite         1.16   16.92   15.76  Mg2Si3O7.5OH:3H2O
        Sepiolite(d)     -1.74   16.92   18.66  Mg2Si3O7.5OH:3H2O
        Siderite        -13.13  -24.02  -10.89  FeCO3
        SiO2(a)          -1.35   -4.06   -2.71  SiO2
        Talc              6.04   27.44   21.40  Mg3Si4O10(OH)2
        Uraninite       -12.67    4.39   17.06  UO2
 
------------------
End of simulation.
------------------
 

The output from the model (table 12) contains several blocks of information delineated by headings. First, the names of the input, output, and database files for the run are listed. Next, all keywords encountered in reading the database file are listed under the heading "Reading data base". Next, the input data, excluding comments and empty lines, is echoed under the heading "Reading input data for simulation 1". The simulation is defined by all input data up to and including the END keyword.

Any comment entered within the simulation with the TITLE keyword is printed next. The title is followed by the heading, "Beginning of initial solution calculations", below which are the results of the speciation calculation for seawater. The concentration data, converted to molality are given under the subheading "Solution composition". For initial solution calculations, the number of moles in solution is numerically equal to molality, because 1 kg of water is assumed. The -water identifier can be used to define a different mass of water for a solution. During batch-reaction calculations, the mass of water may change and the moles in the aqueous phase will not exactly equal the molality of a constituent. Note that the molality of dissolved oxygen that produces a log partial pressure of -0.7 has been calculated and is annotated in the output.

After the subheading "Description of solution", some of the properties listed in the first block of output are equal to their input values and some are calculated. In this example, pH, pe, and temperature are equal to the input values. The ionic strength, total carbon (alkalinity was the input datum), total inorganic carbon ("Total CO2"), electrical balance, and percent error have been calculated by the model.

Under the subheading "Redox couples" the pe and Eh are printed for each redox couple for which data were available, in this case, ammonium/nitrate and water/dissolved oxygen.

Under the subheading "Distribution of species", the molalities, activities, and activity coefficients of all species of each element and element valence state are listed. The lists are alphabetical by element name and descending in terms of molality within each element or element valence state. Beside the name of each element or element valence state, the total molality is given.

Finally, under the subheading "Saturation indices", saturation indices for all minerals that are appropriate for the given analytical data are listed alphabetically by phase name near the end of the output. The saturation index is given in the column headed "SI", followed by the columns for the log of the ion activity product ("log IAP") and the log of the solubility constant ("log KT"). The chemical formulas for each of the phases is printed in the right-hand column. Note for example, that no aluminum bearing minerals are included because aluminum was not included in the analytical data. Also note that mackinawite (FeS) and other sulfide minerals are not included in the output because no analytical data were specified for S(-2). If a concentration for S [instead of S(6)] or S(-2) had been entered, then a concentration of S(-2) would have been calculated and a saturation index for mackinawite and other sulfide minerals would have been calculated.


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