I am trying to model the concentrations (mol/L) measured from a column leaching experiment using solidified incinerated ashes and distilled water. Following the examples of cation exchange and transport and dissolution of Gypsum and calcite from the computer session manual.
The input set up I am using is with solute transport- HP1 a 30 cm depth (length of column), 28 days, measured hydraulic parameters from the material (in this case the ash). I am using constant pressure head for upper BC and free drainage for the lower BC. The solution composition set up consist with an initial solution 1001 with equilibrium phases (minerals in the ash) and distilled water into column with solution 3001. The geochemical model consists of the equilibrium mineral phases with the amounts (mol/cm^3) converted from the total cumulative amount of each element at the end of the column leaching test distributed in each mineral.
Solute transport BC are:
Upper BC: Concentration BC (solution 3001)
Lower BC: zero concentration gradient
For the profile information I am using two nodes at 15cm and 30cm with the column divided in 31 nodes
I think my problem is with the pressure head if I do 0 pressure head in the entire profile (like in the examples) I get no movement of the concentrations through time, just a drop on the first day. But when the pressure head distribution is; Top value: -20 and bottom value -100 I can get movement in both of the observation nodes for the 28 day period but even the first concentration is too high compared to the results of my experiment. I have tried reducing the amounts of the minerals but the HP1 calculated results are always higher.
Sorry for the long text
, any comments or advice are welcome. Santiago