PHREEQC can do 1D transport calculations considering only diffusion. However, all species have the same diffusion coefficient. I don't know if this is a problem for you. If not, you should be able to set up a simulation. You need to use the TRANSPORT data block, but you also need SOLUTION and possibly other data blocks to describe the initial conditions for the column. In TRANSPORT, you need to set "-flow_direction diffusion_only" and specify a diffusion coefficient with " -diffusion_coefficient". David David Parkhurst (dlpark@xxxxxxxx) U.S. Geological Survey Box 25046, MS 413 Denver Federal Center Denver, CO 80225 "Vicky Peacey" <vpeacey@xxxxxx> To: "David L Parkhurst" <dlpark@xxxxxxxx> cc: In-Reply-To: <001901c16949$b4490d20$d5de6481@xxxxxxxxxxxx> 11/09/01 11:09 Subject: transport modeling question AM Dear Mr.Parkhurst, Is it possible to do diffusion modeling using PHREEQC? I've tried using POLLUTE, but it doesn't do upwards diffusion. I have a laboratory diffusion cell and I am trying to model upwards diffusion of metals from the tailings into a clean overlying water cover and then estimate diffusion coefficients of metals. Initially, the water has a concentration of zero, and each day the concentration of contaminants increased in the water cover, until an equilibrium value was reached. I know the pore water and solid elemental concentrations of contaminants in the tailings. Thanks, Vicky Peacey
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