[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: weird phreeqc question

> Something weird is going on with my phreeqc simulations.  Biodegradation
work if coupled with dispersion, sorption, and/or gas phase.  It will NOT
work if I take those processes out.  The error I'm getting is that there
negative moles in solution after transport step 9.  How can there be
moles in solution if I have the line "If Benzene <= 0 then goto 200?"  I've

changed the 0 to 1e-30, 1e-10, etc.  and it seems that phreeqc isn't even
reading that line.  Any suggestions?

Did the messages say Warning or Error. If it said "Warning", then the
program probably ran ok. If it was "Error", then the program failed. If the
program failed, please send your database and I'll look at the problem.

PHREEQC uses a Runge-Kutta method for integrating rate equations. It
estimates rates at various time points and then combines them to estimate a
rate for the entire time interval. Even if rates result in positive
concentrations at each time point, it is possible to calculate a rate that
causes a negative concentration when all of the estimates are combined.
PHREEQC should go back and use a smaller time interval and re-integrate the

If the warning messages are a nuisance, you can specify "-warnings false"
in the TRANSPORT data block.


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

Project Home Page
Complete Water Resources Division Software
USGS Home Page
Water Resources Division Home Page
NRP Home Page
Help Page
USGS Privacy Statement       

Please note that some U.S. Geological Survey (USGS) information accessed through this page may be preliminary in nature and presented prior to final review and approval by the Director of the USGS. This information is provided with the understanding that it is not guaranteed to be correct or complete and conclusions drawn from such information are the sole responsibility of the user.

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. 

The URL of this page is: https://wwwbrr.cr.usgs.gov/projects/GWC_coupled/phreeqc/mail/msg00124.html
Last modified: $Date: 2005-09-13 21:04:21 -0600 (Tue, 13 Sep 2005) $
Visitor number 2821 since Jan 22, 1998.