Re: DOC in PHREEQC

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

> I will be using PHREEQC to model soil & ground water controls on solute
fluxes with Jamie Shanley at the Sleepers River WEBB site.

Great. I think there must be a good story there with all the information
they have collected.

> I first posed this question to Don Siegel since he taught an Aqueous
Geochem course using PHREEQC last spring and he suggested writing directly
to you.  I have dissolved organic carbon data and want to include these
data in model runs.  Can DOC be incorporated into PHREEQC as concentration
input data?  I have not had any luck when looking through the manual for
DOC as a solution species.  Can you direct me to any resources regarding
DOC as an input parameter to PHREEQ?

I'm not sure what you want to do with the DOC in the model. The wateq4f.dat
has Fulvate and Humate defined, but that is only useful for metal-binding
calculations. You can define a Doc "element" with SOLUTION_MASTER_SPECIES
and SOLUTION_SPECIES and then enter the Doc, but that would essentially
produce a conservative element that moves with the water. You could expand
on that and react the Doc by using a KINETIC reaction (and associated RATE)
that removes Doc and introduces C, 2H, and O into the solution, which would
simulate organic decomposition, but maybe that isn't a big reaction at
Sleepers River?

So if you tell me what you really need to calculate, I can probably give
you some advice on how to proceed.

David

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