Charge balance calculation error in GSS

[Jono]

Has anyone experienced a problem when adding the charge balance calculation to GSS? I receive the error message "The Parameter is Incorrect" (see attached .doc file) when trying to add the calculation for charge imbalance or charge imbalance error.

 

The calculation methodology for charge balance error in GSS/SPEC8/REACT was questioned at the Canberra course. Correct me if I am wrong but the method that is most widely adopted is as follows:

 

Balance error% = (cat-an)/(cat+an)*100

 

Is it likely that the same methodology will be employed in a patch/upgrade to GWB in the future?

 

Cheers

Jono

Errro_msg_1.doc

[Tom Meuzelaar]

Hi Jono:

 

The error you see is just a result of setting your SO4 concentration to zero. If you remove this analyte, or replace it with a "n/d" or blank field, all of the options in the Data - Calculate menu will work fine.

 

Let me see what I can find out about method of charge balance calculation.....

 

Regards,

 

Tom

[Tom Meuzelaar]

Hi Jono:

 

The error you see is just a result of setting your SO4 concentration to zero. If you remove this analyte, or replace it with a "n/d" or blank field, all of the options in the Data - Calculate menu will work fine.

 

Let me see what I can find out about method of charge balance calculation.....

 

Regards,

 

Tom

 

Hi Jono:

 

As a follow-up to my first response, note two things:

 

1. There are cases where a zero (or even negative) value is appropriate in GWB speciation calculations- for more on this refer to Geochemical and Biogeochemical Reaction Modeling chapter 3, p. 37-38 (differentiation between species and components, and components with negative masses). In the next patch (8.0.6), we'll make the 'parameter is incorrect' a bit more descriptive

 

2. In versions 8 to 8.0.4, if titration alkalinity is used as input, charge balance may be off by as much as 50% due to a bug that has just been fixed in the latest patch, 8.0.5. For more information on this, please visit this thread. Let's be sure that this is not the reason for the discrepancy you are seeing...

 

I'll follow up with one final post regarding method of calculation.

 

Regards,

 

Tom

[Tom Meuzelaar]

Let me see what I can find out about method of charge balance calculation.....

 

Hi Jono:

 

Here's how GWB calculates charge imbalance (meq/kg) and % error:

 

• Charge imbalance:
   
  

  charge_imbal = (charge_cation - charge_anion)/(1.e-3 * g_soln);

  
   
  

• % error:
   
  

     if (charge_total > 0.0)
       charge_impct = 100.0 * (charge_cation - charge_anion) / (0.5 * charge_total);
    else
       charge_impct = 0.0;

  
   
  

 

I hope that helps,

 

Tom Meuzelaar

RockWare, Inc.