Sorry I didn't explain the process clearly. I assume the sorption of Cu by organicmatter site (Org_x) as follow (see Table 6.6, Werner Stumm, 1995, the book: Aquatic Chemistry): Cu+2 + Org_xH2 = Org_xCu + 2H+ To the formula of Org_xh, I mean H is 0 (zero), not H O. Maybe as you said, it's not necessary to mention this kinetic expression as it has the same rate like Org_xcu. cheers, xiaomin David L Parkhurst wrote: > >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: http://wwwbrr.cr.usgs.gov/projects/GWC_coupled
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