Does phreeqc account for density-driven convection?

[maxim.yutkin]

Hi everyone,

I was wondering if phreeqc accouns for density gradient in diffusive transport.

If I model the following case for a vertical column, how can I take into account density-driven convection? Should I increase diffusion coefficient (can possibly violate boundary conditions?) or introduce extra flow rate somehow?

Code: [Select]

SOLUTION 1
-units mol/L
Na 1
Cl 1
pH 7 charge

SOLUTION 2-10
pH 7 charge

TRANSPORT
    -cells                 10
    -shifts                25
    -time_step             86400
    -flow_direction        diffusion_only
    -boundary_conditions   constant closed
    -lengths               10*0.03
    -dispersivities        10*0
    -correct_disp          true
    -diffusion_coefficient 2.0e-9
    -print_cells           5
    -print_frequency       1
    -punch_cells           5
    -punch_frequency       1
    -warnings              false


[dlparkhurst]

No, PHREEQC does not account for density-driven convection.

On the other hand, there is no convection in a diffusion-only simulation. Also, I am not sure you can adequately model density effects in 1D. If density effects are important, you probably need another model.