Processes > Inverse modelling
Preventing Mineral Dissolution/Precipitation
ztwatson:
Thanks dlparkhurst.
I have a question about the balances for specific elements. Using 0.2 (20%) allows the model to put out a fair amount of potential mixes. Though I worry that this value is too high.
To make sure I understand what the 20% means, if I have 7 mmol of K then the model is allowed to add or subtract 1.4 mmol of K to the specific solution prior to mixing?
dlparkhurst:
Correct. Note that it applies to each solution, so that each solution could change the potassium concentration by up to +/1 20%. The optimization method tries to minimize the sum of the relative changes.
ztwatson:
I thought each column of balances refers to their respective position. So first column refers to solution 1, second to solution 2 etc. Balances is merely a way of addressing the uncertainty of a specific element in a specific solution.
And then the uncertainty applies to all elements in all solutions. If the balance values are greater than the uncertainty value, then they override the uncertainty.
correct?
Also, when I click on balances in the toolbar a comment in the bottom comes up stating
"Any element not present in the phases to be used"
What does this mean?
dlparkhurst:
I thought each column of balances refers to their respective position. So first column refers to solution 1, second to solution 2 etc. Balances is merely a way of addressing the uncertainty of a specific element in a specific solution.
Q. And then the uncertainty applies to all elements in all solutions. If the balance values are greater than the uncertainty value, then they override the uncertainty.
A. -balance allows an uncertainty to be entered for each solution. If fewer uncertainties are entered than the number of solutions, the final uncertainty is applied to the remaining solutions. -balance overrides the uncertainty defined by -uncertainty, whether it is larger or smaller.
Q. Also, when I click on balances in the toolbar a comment in the bottom comes up stating
"Any element not present in the phases to be used"
What does this mean?
A. By default, any element in any mineral is included in the set of mole-balance equations. (There is no way to remove any of these mole-balance equations except by removing all minerals that contain an element.) -balances can be used to include elements that are not present in any of the minerals. For example, if you do not want to include a Cl-containing mineral, but you want to include a Cl mole-balance equation as a conservative constituent, then you can add the Cl mole-balance equation with -balance.
ztwatson:
I am trying to add strontium to my model as another element. However whenever I type in Sr (which is what I assume its abbreviation would be) it becomes italicized. Is Sr and abbreviation for something else?
How do I put strontium into Phreeqc?
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