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Hello.
I want to build in Act2 a graph of this kind as in the attached image.
The question is how do I set the values for the axes: Y - log [Ca2 +] * [Mg2 +], X - log [CO32 -] ^ 2?

 

The second question is, as I understand it, the program itself selects mineral phases from the database depending on the set of components. 
Can I forcibly ban the display of certain minerals on the diagram, or is it necessary to remove them from the database?

CaMgCO3.jpg.3ab7eef8f94de2ccc72bce38244401c0.jpg

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Hello Ulagai,

You can set activity ratios (e.g. aK+/aH+)  in the x and y axes but cannot simply raise the activity of species to a certain power. Please see section 5.1 Diagram calculation in the Essentials User Guide for examples. 
 
You can use the suppress function to suppress minerals that are unlikely  to be forming in your system. To suppress minerals, go to 'Config' --> Suppress and select the minerals/species you wish to suppress. For more information regarding the the suppress feature, please refer to the GWB Command Reference guide. 
 
Hope this helps.
 
Best regards,
Jia Wang

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Hello Ulagai,

On another thought, I think you will find Rxn useful. You can calculate the equilibrium equation for dolomite (CaMg(CO3)2) using Rxn and make the activity-activity plot manually. To do so, you would open up Rxn and balance the reaction for Dolomite. When you select dolomite, Rxn will automatically balance dolomite in terms of the original basis species, which is Ca++, Mg++, H+, and HCO3-. You can have Rxn write the equilibrium equation in terms of CO3-- by swapping it with HCO3-.  If you wish, you can then enter the activity value for CO3-- and have the equation be simplified and solve for log[Mg++] + log[Ca++], which equivalent to the y-axis of the plot you attached. 

Please refer to section 4.2 Calculating equilibrium equations in the GWB Essential guide for more information and examples. 

Hope this helps,

Jia

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Thank you very much for your answers.

 

I have one more question. I introduced a new component of an aqueous solution (H4SiO4) at TEdit. And I wanted to calculate Log K's for him in Rxn. However, in Rxn it is not in the "Balance reaction for" list. What am I doing wrong?

TEdit.thumb.jpg.3d0eeffea74ef9b17e98fac207ff5df8.jpg

Rxn.jpg.6a4d1a9adbd5c9cf5ef902a4f2564b98.jpg

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I understood what was happening - I did not have any log K's set. Honestly, I just calculated with the help of Rxn the value of log K for 25 degrees, based on the known values for H2O b SiO2. Apparently this is not possible?

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Hello Ulagai,


When you create a new species in the thermo database, in this case H2SiO4, you will need to provide at least one Log K value at one of the 8 principal temperatures. Most commonly, the Log K value is derived at 25 degree Celsius. If you do not enter any Log K values, the GWB programs will not read in the new species you have added. Once you have successfully added in the new species, you should be able to add the species in Rxn and balance reactions. Where the temperature differ from a principal temperature, the application fits non-'500' values to a polynomial. You can expand the results in the Results pane and obtain the temperature polynomial equation the program uses to estimate LogKs with the principal temperature range. While the GWB can extrapolate beyond this range in calculations using the 'extrapolate' option, I would advise to do so cautiously. 

Please note that starting with GWB14, the thermo database can alternatively carry temperature expansions for log Ks for a range of valid temperature. The method above is for T-table logK approximation for older formatted GWB datasets. Please refer to section 9 in the GWB Essentials Users guide for more information regarding editing thermo datasets in TEdit. 


Hope this helps,
Jia Wang

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Hello.
Thank you for your responses.
One more question. Due to the specific composition of the studied waters, I simultaneously inject HCO3 and CO3 into GSS.
As I understand it, there is no such possibility (without manual recounting).
There is an idea to transfer CO3 from "Acueous species" to "Basis species. Is this permissible and how does this affect the program.

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Hello Ulagai,


You can enter basis species into the GSS spreadsheet. For your specify question though, HCO3- and CO3-- are both carbonate species. When you enter HCO3- into the database, you are effectively including the sum of the thermodynamic component (e.g. CO2(aq), CO3--, NaHCO3-, etc). If you wish to enter the concentration of HCO3- without the additional species, you will need to enter the species as a free constraint. To do so, you can right click on the unit for HCO3- and select "free". 


I would not recommend moving CO3-- from aqueous to basis species since components chosen as a basis species must be linearly independent from one another. In this case, HCO3- is the basis species and CO3-- is an aqueous species can be written in terms of HCO3- and H+.  You can alternatively add CO3-- as a user defined analyte if you simply want to keep track of how much CO3-- is in your system. But keep in mind, you cannot use user defined analytes in GWB apps for simulations. For more information on how to create your own user analyte, please refer to section 3.3 in the GWB Essentials User guide. 


Hope this helps,
Jia Wang

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