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 ----- Forwarded by David L Parkhurst/WRD/USGS/DOI on 05/27/03 01:48 PM ----- David L Parkhurst To: xiaomin Mao <xmao@xxxxxxxx> 05/27/03 01:45 PM cc: Subject: Re: PHREEQC problem(Document link: David L Parkhurst) >About (1), I don't understand why you write: H -2 Cu +1 OH -1. I write in the kinetic expression: -Formula H -2.0 Cu +1 will it be any problem? I combined your two expressions ( Org_xcu and Org_xh) because they have the same rate expression. The combined formulas do not appear to be charge balanced to me. Your calculated rate is negative I believe, so with -formula H -2 Cu +1, you would be removing copper and adding H to solution. For Org_xh the rate is positive, so with -formula O H, you are adding OH to solution. The net reaction is relative to solution is Cu -1 H +2 OH +1 or Cu -1 H +3 O +1. What is the reaction that you are trying to model? SOH + Cu+2 = SOCu+ + H+ ? You probably need to add the counter ion for such a reaction to make sure the solution does not get imbalanced. (SURFACE calculations add an inert charge to account for this effect.) SOH + Cu+2 + Cl- = SOCuCl + H+ So the -Formula CuCl -1 H +1 would be appropriate. But maybe this is not what your are trying to model. > To (2), I think I have noticed the difference. TOT is used to get the concentration of Cu in the solution which is required according to the model. As the water in each cell is only 0.03375 kg, the organic matter is calculated based on the quantity of soil and ratio of organic matter in each cell. therefore, it seems not to be the problem. If you say so. I would still try a simpler rate expression to see whether the problem is in the rate expression or some other part of the kinetic definition. 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
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