Direct transfer mass flux links are used to transport mass directly from one pathway to another via a mechanism that cannot be appropriately represented as either advection or diffusion. They are defined by specifying a fractional rate at which mass is being moved from one pathway to another. Hence, a direct transfer mass flux is computed as the mass of the species The chemical (or non-chemical, such as bacterial or viral) constituents that are stored and transported through an environmental system in a contaminant transport model. In GoldSim, the Species element defines all of the contaminant species being simulated (and their properties). in the pathway multiplied by a fractional transfer rate:
Direct Transfer Mass Flux = Cell Mass * Transfer Rate
The Transfer Rate has dimensions An output attribute for an element that defines the dimensionality (in terms of Length, Time and other fundamental dimensions) of the output. of inverse time. The Transfer Rate is specified as a vector A one-dimensional array. by species, which allows the Transfer Rate to be species-specific.
As an example of how you might apply a direct transfer mass flux link, consider the following. Suppose that you were simulating the transfer of mass from soil to a plant. You want to represent the kinetics of the transfer process (i.e., you do not want to assume immediate equilibrium). The transfer rate is first order (i.e., proportional to the mass of species in the soil), but cannot be adequately represented as advection (no fluid is moving between the soil and the plant) or diffusion (for example, perhaps the transfer rate is not a function of the concentration of the species in the plant). You could use a direct transfer mass flux link An interconnnection between two transport pathways that defines the rate at which species move between the pathways. to represent the kinetics in this case.