Features and Capabilities of Cells

A Cell pathway A transport pathway element that is mathematically equivalent to a finite difference node. Cells are commonly applied to simulate discrete compartments in an environmental system (such as ponds, lakes, shallow soil compartments, or the atmosphere). is mathematically equivalent to a mixing cell, and can explicitly represent the following processes:

• Partitioning. You can assign multiple fluid or solid media Materials (such as water, sand, clay, air) that constitute (are contained within) transport pathways. GoldSim provides two types of elements for defining media: Fluids and Solids. (e.g., water, oil, rust, soil) to a Cell, and specify partition coefficients The ratio of the species’ concentration in a medium to its concentration in the Reference Fluid at equilibrium. Partition coefficients are inputs to Solid and Fluid elements. between the various media. Contaminant mass is 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 Reference Fluid A special type of Fluid element that provides a basis for defining partition coefficients between media for the various species in the model (i.e., the ratio of the species’ concentration in the medium to its concentration in the Reference Fluid at equilibrium). (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 (using advective and diffusive mass flux links). Other transport mechanisms can also be represented by using direct transfer mass flux links. 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.

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. GoldSim numerically solves the coupled system of equations to compute the contaminant mass present in each Cell (and the mass transfer rates between Cells) as a function of time.

The following topics describe the basic assumptions incorporated into Cell pathways, and how to define and use them in your models.The mathematical and computational details of how Cell pathways are implemented within GoldSim are provided in Appendix B of the Contaminant Transport Module User’s Guide.