Mr. Parkhurst, I have a question for you about PHREEQ-C: you mention in the manual that the usage of mole fraction for the activity of surface species instead of molarity (which sounds reasonable to me) does affect multidentate complexes - I'd be interested in how this affects bi- or tridentate complexes. In addition, I was wondering if it is possible to include surface precipitation as well in PHREEQ-C (accounting for the phenomenon that near the surface concentrations may be high enough for precipitation whereas overall solution concentrations are too low for precipitation to occur). I simulated As(V) sorption onto a quartz sand using the diffuse double layer model, and I had some problems at "higher" As(V) concentrations - at 10^-7 and 10^-8 moles/l As(V) the model works fine, but it underpredicts sorption at 10^-6 moles/l and I was wondering if that could be due to bidentate complexes involved (which was observed in other studies) or surface precipitation with dissolved Fe. Thanks for you help. Birgit -----Original Message----- From: David L Parkhurst [mailto:dlpark@xxxxxxxx] Sent: Thursday, February 13, 2003 4:37 PM To: Birgit Braun Subject: Re: PHREEQ-C mailing list Ok. Your name will be added to the PHREEQC mailing list. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Dipl.-Ing. Birgit Braun, M.S. Reserach Associate Colorado School of Mines Department of Environmental Science and Engineering Golden, CO 80401 Phone: (303) 384 2116 Email: bbraun@xxxxxxxxx
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