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Hello,

 

I am interested in calculating the charge balance of some chemical analyses and representing them graphically (e.g. with a pie graph in units of meq).

The question I have is how to represent species that can be present in multiple valences (e.g. Fe).  The default for Fe in GSS is as Fe+++, which is likely to be true for some of my samples, but not all.  Do I need to do a SpecE8 run first and specify some kind of redox conditions in order to have Fe as both Fe++ and Fe+++?  This question would apply to other elements with multiple charge states.  When I calculate charge balance within the GSS program, is a speciation calculation run for the solution?

 

Thanks,

 

Spencer

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  • 2 weeks later...

Hello Spencer,

For your example of Fe++ and Fe+++, you can enter both valences on your spreadsheet if you decouple the redox coupling reactions between Fe+++ and Fe++. Decoupling the reaction will make Fe+++ available to add as a basis species to your spreadsheet. Secondary parameters such as charge imbalance and mineral saturation indices are done using SpecE8 for each fluid entry.

Hope this helps,

Jia Wang

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  • 2 weeks later...

Hello Jia,

Thanks for the reply.

Good to know I can manually specify the redox distribution by decoupling.

What I was thinking I would like to do was to enter total iron, then enter either a redox couple (e.g. O(0)/O(-2) or my pe measurement, or specify redox equillibrium with a mineral phase (e.g. pyrite), and then speciate all redox species based on that.

Is that possible to do?

If so, can you help me with how to do it?

Thanks,

 

Spencer

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Hello Spencer,

You can certainly calculate the redox species speciation given the proper constraints (e.g. the Eh or O2(aq) concentration) and total component concentration. GSS can use SpecE8 to calculate values for your spreadsheet, including species concentration. To do so, go to "+ analyte" and select "Calculate with SpecE8". Then select species concentration for variable type. In your example, you would select Fe+++ and Fe++. The species concentration calculated should be added to your spreadsheet once you hit apply at the bottom of the analyte dialog.

Not that that the order of the analytes in the data sheet is important. In its calculations, SpecE8 will use the first constraint it finds for a particular basis component. For example, if both Eh and O2(aq) are present, SpecE8 will use whichever is first in the data sheet. You can easily change the order of the analytes by dragging, or hide analytes you don’t want used in the calculations. For more information, please refer to section 3.2.5 Calculating analytes in the GWB Essentials User Guide.

Hope this helps,

Jia Wang

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Thanks Jia, very helpful.

I think I am almost there.  I can calculate the concentrations of the various species as you describe.

However, using the Graphs -> Pie Chart (or Bar Chart) option in GSS, all of the iron is still listed as Fe++, but from doing the calculations, I know that most of the iron is present as Fe(3) (mostly FeSO4+).  Does the "Fe++" on the bar chart just mean that that portion of cations is from the BASIS species (Fe++), and not actually Iron in the Fe(2) state?

Also, I assume that "total component concentration" would be Fe in the original basis species (Fe++)?

 

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Hello Spencer,

Glad to hear that you are getting closer. The concentration you enter for the basis species represents the total component composition (e.g. Fe++, Fe+++, FeSO4+, FeCl+). In a bar graph, the concentration displayed assumes the concentration reflects the oxidation state of the analyte you have chosen, in this case Fe++. I think you might want to add in Fe+++ and represent the concentration for that analyte separately and select "free" unit for Fe++ and Fe+++.  You can show all ions in the bar plot by unchecking "Common ions" in the parameters for Bar Chart dialog. Please see section 8.1 Plots type for an example. 

Hope this helps,

Jia

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Thanks again, sorry to belabor this, but I just can't seem to make these plots in a way that actually reflect the data, as explained below.

I had gone over section 8.1 and de-selected "common ions".

Something still seems wrong, but I can't figure out what.

One thing I notice is that the bar chart (posted above) would seem to indicate about double the amount of ionic strength as what the results show (see text results below from SpecE8 for this water).

I ended up making the plot I wanted using a combination of PHREEQC and Python, included below.  The ionic strength is pretty consistent with that reported by the SpecE8 results, and it shows the major species that make up the composition of the solution, not just the basis species.

I have tried to replicate this in GWB by doing as you suggest (adding or swapping basis species), but no luck so far.

          Temperature =  25.0 C    Pressure =  1.013 bars
          pH =  2.510              log fO2 =  -26.406
          Eh =   0.6900 volts      pe =  11.6642
          Ionic strength      =    0.187967 molal
          Charge imbalance    =    0.014914 eq/kg (7.833% error)
          Activity of water   =    1.000000
          Solvent mass        =      1.0000 kg
          Solution mass       =      1.0124 kg
          Mineral mass        =     0.00000 kg
          Solution density    =    1.019    g/cm3
          Solution viscosity  =    0.009    poise
          Chlorinity          =    0.000000 molal
          Dissolved solids    =       12210 mg/kg sol'n
          Elect. conductivity =     8336.46 uS/cm (or umho/cm)
          Hardness            =     2681.46 mg/kg sol'n as CaCO3
          Water type          =    Mn-SO4
          Bulk volume         =        994. cm3
          Fluid volume        =        994. cm3
          Mineral volume      =       0.000 cm3
          Inert volume        =       0.000 cm3
          Porosity            =        100. %
          Permeability        =        98.7 cm2

  Nernst redox couples                                 Eh (volts)     pe
 ----------------------------------------------------------------------------
   e-  + H+  + .25 O2(aq)  = .5 H2O                       0.6900   11.6642

  No minerals in system.

  Aqueous species       molality    mg/kg sol'n    act. coef.     log act.
 ---------------------------------------------------------------------------
   SO4--                  0.04130         3919.      0.2786       -1.9390
   Mn++                   0.01958         1062.      0.3399       -2.1769
   MnSO4                  0.01480         2207.      1.0000       -1.8297
   Fe++                   0.01175         648.0      0.3399       -2.3987
   Mg++                  0.008345         200.3      0.3934       -2.4838
   FeSO4                 0.007277         1092.      1.0000       -2.1380
   Ca++                  0.006824         270.2      0.3399       -2.6346
   MgSO4                 0.006378         758.3      1.0000       -2.1953
   CaSO4                 0.005576         749.8      1.0000       -2.2537
   HSO4-                 0.004752         455.7      0.7363       -2.4560
   H+                    0.003794         3.777      0.8146       -2.5100
   AlSO4+                0.001625         197.4      0.7363       -2.9222
   Al(SO4)2-             0.001462         316.4      0.7363       -2.9680
   Zn++                  0.001348         87.07      0.3399       -3.3388
   ZnSO4                 0.001236         197.1      1.0000       -2.9079
   Al+++                0.0007423         19.78      0.1370       -3.9928
   AlF++                0.0002196         9.973      0.3103       -4.1666
   K+                   0.0001531         5.913      0.7129       -3.9620
   SiO2(aq)             0.0001208         7.167      1.0491       -3.8972
   KSO4-                1.214e-05         1.621      0.7363       -5.0486
   Cd++                 3.421e-06        0.3799      0.1332       -6.3411
   AlF2+                2.469e-06        0.1585      0.7363       -5.7404
   CdSO4(aq)            1.513e-06        0.3115      1.0000       -5.8202
   Cd(SO4)2--           1.433e-06        0.4309      0.1332       -6.7192
   AlOH++               1.233e-06       0.05357      0.3103       -6.4173
   HF                   3.064e-07      0.006055      1.0000       -6.5137
   F-                   9.258e-08      0.001737      0.7250       -7.1731
   MgF+                 1.886e-08     0.0008068      0.7363       -7.8574
   MnF+                 1.327e-08     0.0009691      0.7363       -8.0101
   FeF+                 1.196e-08     0.0008841      0.7363       -8.0553
   H2SO4                1.068e-08      0.001035      1.0000       -7.9712
   CaF+                 2.664e-09     0.0001554      0.7363       -8.7075
   AlF3                 1.532e-09     0.0001271      1.0000       -8.8147
   Al(OH)2+             1.139e-09     6.865e-05      0.7363       -9.0763
   ZnF+                 7.515e-10     6.263e-05      0.7363       -9.2571
   Al2(OH)2++++         5.360e-10     4.658e-05      0.0428      -10.6399
   FeOH+                1.162e-10     8.364e-06      0.7363      -10.0677
   MnOH+                7.540e-11     5.359e-06      0.7363      -10.2556
   H3SiO4-              8.648e-12     8.124e-07      0.7363      -11.1960
   OH-                  4.601e-12     7.729e-08      0.7250      -11.4768
   Mn2OH+++             3.331e-12     4.175e-07      0.1199      -12.3988
   MgOH+                2.335e-12     9.531e-08      0.7363      -11.7646
   MgH3SiO4+            9.342e-13     1.102e-07      0.7363      -12.1625
   CaH3SiO4+            3.750e-13     5.008e-08      0.7363      -12.5589
   H2F2                 2.516e-13     9.943e-09      1.0000      -12.5993
   Al(OH)3              2.347e-13     1.808e-08      1.0000      -12.6295
   CaOH+                2.088e-13     1.177e-08      0.7363      -12.8133
   HF2-                 8.831e-14     3.403e-09      0.7363      -13.1869
   AlF4-                3.507e-14     3.567e-09      0.7363      -13.5881
   Al3(OH)4(5+)         2.206e-14     3.247e-09      0.0072      -15.7998
   CdOH+                2.004e-14     2.562e-09      0.6123      -13.9111
   Mg2OH+++             1.255e-15     8.132e-11      0.1199      -15.8228
   KOH                  1.156e-16     6.404e-12      1.0000      -15.9372
   Al(OH)4-             1.056e-16     9.906e-12      0.7363      -16.1095
   AlF5--               4.609e-19     5.553e-14      0.2786      -18.8914
   MgH2SiO4             4.587e-19     5.365e-14      1.0000      -18.3384
   Fe(OH)2              1.582e-19     1.404e-14      1.0000      -18.8009
   Mn(OH)2              4.435e-20     3.897e-15      1.0000      -19.3531
   CaH2SiO4             2.735e-20     3.625e-15      1.0000      -19.5630
   Mg(H3SiO4)2          1.599e-20     3.387e-15      1.0000      -19.7963
   Mn2(OH)3+            2.594e-21     4.122e-16      0.7363      -20.7191
   Ca(H3SiO4)2          1.336e-21     3.039e-16      1.0000      -20.8742
   H2SiO4--             5.896e-22     5.480e-17      0.2786      -21.7844
   Cd(OH)2(aq)          2.132e-22     3.084e-17      1.0000      -21.6711
   H6(H2SiO4)4--        3.564e-24     1.346e-18      0.2786      -24.0031
   AlF6---              8.397e-26     1.169e-20      0.0552      -26.3342
   SiF6--               5.848e-27     8.207e-22      0.2786      -26.7880
   Mn(OH)3-             1.870e-29     1.957e-24      0.7363      -28.8611
   Fe(OH)3-             1.096e-29     1.157e-24      0.7363      -29.0932
   O2(aq)               4.723e-30     1.493e-25      1.0491      -29.3050
   H2(aq)               3.302e-32     6.575e-29      1.0491      -31.4604
   Cd(OH)3-             1.265e-32     2.041e-27      0.6123      -32.1111
   Mg4(OH)4++++         6.666e-39     1.088e-33      0.0428      -39.5452
   H4(H2SiO4)4----      9.174e-40     3.448e-34      0.0057      -41.2805
   Mn(OH)4--            1.337e-40     1.624e-35      0.2786      -40.4289
   Cd(OH)4--            1.676e-43     2.987e-38      0.1332      -43.6511
   MnO4-                3.648e-52     4.286e-47      0.7363      -51.5709
   MnO4--               5.045e-54     5.927e-49      0.2786      -53.8522
   Al13O4(OH)24(7+)     8.224e-67     6.685e-61      0.0001      -70.2934
   H2S(aq)              1.805e-80     6.077e-76      1.0000      -79.7434
   HS-                  9.042e-85     2.953e-80      0.7250      -84.1834
   S--                  8.543e-96     2.705e-91      0.3103      -95.5766
   S2--                5.318e-151    3.368e-146      0.2786     -150.8292
   S3--                8.189e-207    7.780e-202      0.2786     -206.6417
   S4--                4.507e-260    5.709e-255      0.2786     -259.9011
   S5--                3.375e-316    5.345e-311      0.2786     -300.0000
   S6--                    0.0000        0.0000      0.2786     -300.0000

Surf_Tails.png.134963166fb897c70720bc4a449ba441.png

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Hello Spencer,

Like I said above, the concentration you enter for Fe++ in the GSS spreadsheet is considered as Fe++ when you are plotting from GSS. So that's why I suggested you adding Fe++ and Fe+++ separately. 

I don't think the graph is showing twice the ionic strength. If you add the individual species of that component, then you should arrive at the same concentration as shown in the plot. For example, if you summed all the sulfate species concentration and covert to meq/kg, then you should get the same value as seen plotted from the GSS spreadsheet. There should be a section below in your SpecE8 output file that shows you the total component concentration for that species (e.g. SO4--). The bar graph type plot does not plot individual species concentration, only component concentration. You can however retrieve each aqueous species concentration in units of eq/kg and make the plot separately in excel or python. To retrieve those values, you can plot your SpecE8 calculation results in Gtplot (in your SpecE8 window go to Results and click on plot results). An XY plot should pop up, if not, you can go to Plot on the menu bar up to and select XY plot. Double click on the center of the plot to bring up the plot configuration. You can configure one of the axis to show the variable type "species concentrations" and change the units to meq/kg (or eq/kg). Click ok or apply. Then go to the Edit --> copy as --> spreadsheet and paste your result into excel to view. You can manipulate this numerical result externally to plot as you wish. 

Hope this helps,
Jia

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Thanks.

If I do as you said for the example of sulfate,  I get the following for by-component equivalents with the bar graph (169.7 meq/kg for SO4--):

Step Xi H2O Al+++ Ca++ Cd++ F- Fe++ H+ K+ Mg++ Mn++ O2(aq) SO4-- SiO2(aq) Zn++
    meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg
0 0 0 12.01042 24.50093 0.012581 0.22226 23.2105 16.23034 0.163255 29.09023 67.92366 0 169.7019 0 5.106747

and the following for Total Sulfate Species (91.05 meq/kg) using the xy plot export procedures and selecting only SO4-- species  (Total 91.05 meq/kg).

Sulfate Species:                                              
Rxn progress Al(SO4)2- AlSO4+ CaSO4 Cd(SO4)2-- CdSO4(aq) Fe(SO4)2- FeHSO4++ FeSO4 FeSO4+ H2S(aq) H2SO4 HS- HSO4- KSO4- MgSO4 MnSO4 S-- S2-- S3-- S4-- S5-- S6-- SO4-- ZnSO4
  meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg meq/kg
0 1.42095 1.629153 0 0.002644 0 1.338236 0.035607 0 6.387276 0 0 8.57E-82 4.508028 0.01168 0 0 1.58E-92 9.45E-148 1.41E-203 7.52E-257 0 0 75.71746 0
 

 

 

                                           

 

So, it appears there is a mismatch, unless I'm still missing something about how these plots are representing the data?

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Hi Spencer,

The bar chart expresses the bulk composition of the fluid in electrical equivalents and does not account for speciation. You can use SpecE8 to calculate the distribution of mass for each component and plot these results in an XY plot as electrical equivalents. The calculated results can be exported and be plotted externally.

Please also note that the axis on the bar chart does not represent ionic strength of the fluid. If you want to check if mass balance is honored, you should use molality as the unit. If you add up the concentration of individual species, you will arrive at the bulk composition of that component.

Best regards,

Jia Wang

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Quote

The bar chart expresses the bulk composition of the fluid in electrical equivalents and does not account for speciation. 

Ah, OK.  This is what I was looking for.  I understand what it is doing now.

It is not really a visualization of charge balance showing the major species, just which basis cations and anions make up the solution.

Quote

Please also note that the axis on the bar chart does not represent ionic strength of the fluid. If you want to check if mass balance is honored, you should use molality as the unit. If you add up the concentration of individual species, you will arrive at the bulk composition of that component.

That makes sense.  I'm not sure what I was thinking with the ionic strength for these charts.

Thanks Again for your help.

Spencer

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