It is not necessary to bias the log K by 20 in PHREEQC. This was a trick for the old PHREEQE program, which include X- in the mole balance equations. The free X- ion was forced to be small by this adjustment to the log K's of the exchange reactions. In PHREEQC, the X- ion is not added into the mole balance equations at all. The cation exchange reactions are half reactions referenced to sodium (log K 0.0) in the default data bases. 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 "Bruno Haerens" <bruno.haerens@xxxxxxxx To: <dlpark@xxxxxxxx> uven.ac.be> cc: Subject: selectivity coefficients 11/10/2003 06:10 AM Dear David, Here I am again with a question: In Appelo's paper in WRR (1994), he mentions in the comments of table 1, that to all log KIX, 20 is added in PHREEQM. I guess this is als still the case in PHREEQC-2, but I didn't find that in the manual. Am I correct here? Best regards, Bruno
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:
Last modified: $Date: 2005-09-13 21:04:21 -0600 (Tue, 13 Sep 2005) $
Visitor number 2476 since Jan 22, 1998.