Simulating Suspended Solids in an Aquifer

GoldSim allows you to specify that suspended Solids are present in the Aquifer. These Solids are assumed to be advected and dispersed along the Aquifer. Species which partition onto the suspended Solids are transported with them as they move through the Pipe.

Suspended solids are specified to be present in the Aquifer via the Suspended Solids… button on the Aquifer dialog. When you press this button, the following dialog is displayed:

An Aquifer can have a single suspended Solid for which you must define the Solid Medium and the Concentration:

Solid Medium: This is the solid suspended in the Aquifer. It must be a previously defined Solid medium.

Concentration: This is the concentration of the suspended solid in the Aquifer fluid. It has dimensions of mass per volume.

Suspended solids in an Aquifer can increase the "carrying capacity" of the pathway fluid, by allowing solute species to sorb onto and be transported by particulates. This has the effect of reducing retardation due to sorption onto infill material. Mathematically, suspended solids in an Aquifer can be thought of as increasing the effective concentration in the pathway fluid, thereby increasing the mass flux of species out of the Aquifer. In particular, assuming no dispersion, the advective mass flux of species i leaving the Aquifer, Flux_i, becomes:

Flux_i = Q cd_i (1 + K_i V_susp c_susp)

where Q is the flow rate in the Aquifer (volume/time), cd_i is the dissolved concentration of species i (mass/volume), K_i is the partition coefficient for species i for the suspended solid medium (volume/mass), c_susp is the suspended solid concentration (mass/volume), and V_susp is the dimensionless Advective Velocity Multiplier for the suspended Solid (a property of the Solid).

Note: The suspended solid concentration only impacts advective mass flux links leaving the Aquifer and does not have any impact on the diffusion of particulates into the Aquifer. That is, if a diffusive mass flux link is created between a Cell containing a suspended solid and an Aquifer containing the same suspended solid, for the purpose of simulating the diffusive flux of particulates, the concentration of particulates on the Aquifer side of the link is assumed to be zero.