Once mass is exposed within a Source, it is available for transport within and away from the source. GoldSim allows both advective and diffusive transport mechanisms to be explicitly represented. Mass transport within and away from a source is controlled by the following:
- Partitioning. The Source can contain multiple fluid and solid transport and storage 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), with 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. Exposed contaminant mass will be partitioned between the various media within the Source based on the partition coefficients and the masses or volumes of the media. This in turn, will affect transport rates.
- Solubility constraints. Solubility limits for the contaminants can be specified within the Source. Precipitated mass can only be transported via advection of the solid media it has precipitated onto.
- Mass transfer. Media flow rates through the Source, geometric considerations, and contaminant properties (e.g., diffusivities) control the advective and diffusive mechanisms by which exposed mass can be transported.
The transport of mass through and away from a Source is actually implemented within GoldSim by associating (i.e., linking) one or more Cell pathways with each Source. Cells that are associated with Sources in this way take on some special properties.