Cell Pathway Features

CELL A Cell pathway is mathematically equivalent to a mixing cell, and can explicitly represent the following processes:

• Partitioning. You can assign multiple fluid or solid media (e.g., water, oil, air, rock, soil) to a Cell, and define species partition coefficients between the various media. Contaminant mass is assumed to be instantaneously and completely mixed and equilibrated throughout the Cell, and contaminants are partitioned between the various media based on the partition coefficients and masses/volumes of the various media present.

• Solubility constraints. You can assign solubility limits for the contaminants in the fluids (typically water) present in the Cell. The dissolved concentration of the contaminants in the Cell cannot exceed the solubility limit. If you are simulating isotopes of the same element, GoldSim ensures that the sum of the concentrations of all isotopes does not exceed the solubility limit.

• Mass transport. You can define the processes and properties controlling the rate at which mass moves between pathways (e.g., from one Cell to another). Both advective and diffusive transport mechanisms can be explicitly represented. You must specify flow rates for advective transport and diffusion coefficients and geometric factors for diffusive transport. You must also specify the media which are being advected (both fluids and solids can be advected), and the media through which diffusion occurs (inter-media diffusion, such as across an air-water interface, can be specified). In addition, solids present in a Cell can be specified to be suspended in the Cell’s fluid media, such that the transport of contaminants on suspended particulates (via advection or diffusion) can be explicitly modeled. For special situations, you can also simulate several transfer processes that cannot be described as either advection or diffusion (direct transfer, treatment, and precipitate removal).

When multiple Cells are linked together via advective and diffusive mechanisms, the behavior of the Cell network is mathematically described using a coupled system of differential equations. In effect, a network of Cells is mathematically equivalent to a finite difference network of nodes. GoldSim numerically solves the coupled system of equations to compute the contaminant mass present in each Cell (and the mass fluxes between Cells) as a function of time.

Cells are commonly applied to simulate discrete compartments in an environmental system (such as ponds, lakes, shallow soil compartments, or the atmosphere). In some situations, a series or network of Cells may also be the best way to simulate features such as aquifers and rivers.