RE: PHREEQC problem

["David L Parkhurst" <dlpark@xxxxxxxx>]

I think the problem probably did not converge when you got the strange X
moles.

I think there is a problem with your problem definition. Right now, you are
adding .01 mol of NaAcetate per day because of the REACTION definition. I
think you probably want to add the NaAcetate once. To do this:

USE solution 1
REACTION
...
SAVE solution 1
END

Follow this set of instructions with the kinetics reaction and do not "USE
reaction 1".

The formula for the kinetic reaction needs to be charge balanced. It should
probably be:

-formula CH3COOH -1 HAcetate 1

 given a negative moles of reaction calculated in the RATES definition.
PHREEQC ignores any charge given in the -formula fields. Think of the
formula in terms of addition or removal of elements from solution, not
aqueous species.  Finally, the check for removal of Acetate in the rate
definition has the wrong sign. Here is an alternative definition.

20 if -moles > tot("Acetate") then moles = -tot("Acetate") #avoid
'overdegradation' (more degradation then Acetate present)
25 if abs(moles) < 1e-11 then moles = 0

This still slows down a bit toward the end of the year, but it seems to
work. A revised file is attached below.

David

(See attached file: Phrqc6.pqi)




David Parkhurst (dlpark@xxxxxxxx)
U.S. Geological Survey
Box 25046, MS 413
Denver Federal Center
Denver, CO 80225

Project web page: https://wwwbrr.cr.usgs.gov/projects/GWC_coupled

Attachment: Phrqc6.pqi
Description: Binary data