> In the PHREEQC database there is two equations for CaCO3: This reaction is for the formation of the CaCO3 ion pair: Ca+2 + CO3-2 = CaCO3 log_k 3.224 This reaction is for the dissolution of calcite: Calcite CaCO3 = CO3-2 + Ca+2 log_k -8.480 > Which one of the equilibrium constants is used by PHREEQC to calculate the solubility constant? The second one is for the solid, calcite. > If both this constants are used doesn't the model became unstable. You could remove the ion pair (give a small log K = -20), but it should not cause any instability. If you are equilibrating with calcite, you need the log K for calcite. 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
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 2011 since Jan 22, 1998.