Specify "charge" in a multi-solution input file?

[toupis12]

Hi all,

Is it possible to have a multi-solution input file and specify a charge balance on one of the ions? Have a really large file and only analyzed cations (plus Si) so many of the samples don't balance, leading to me having to manually run the file many times without the samples that don't balance. Wondering if there is a better method that may save me some time.

Thank you!

[dlparkhurst]

First, I'm not sure what you can do if you only have cations. Most saturation indices are based on ion-activity-products that include anions and cations. Hopefully, you have pH measurements, but I'm skeptical that the data are suitable for geochemical modeling.

But, in answer to your question, it is possible to define a charge-balance ion (or pH) for a large number of solutions. The SOLUTION_SPREAD keyword allows you to define a table of data, with analyte definitions for the columns (pH, Ca, Mg, ...) and each row defining a sample. The data may be cut and pasted from Excel. It is possible to specify one of the columns to be adjusted to equilibrium.

The tabs necessary to make this file work often are removed in posting this message, so the following may not work, but if you enter it through IPhreeqc, you will see the results. Selecting the charge-balance species is in through the Units/Option tab of the SOLUTION_SPREAD screen.

Code: [Select]

SOLUTION_SPREAD
 pH     Na        Cl
             charge
  7    0.1         1
  7      1         1
  7     10         1