A mass transport model simulates the movement of 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). between pathways. Hence, the pathways that you create must be interconnected into a pathway network before you can simulate contaminant transport.
Pathways are connected together into a network by creating mass flux links between pathways. Mass flux links control the rate at which each species is transported between pathways. Mass flux links are created from tabs (Inflows, Outflows, and Diffusive Fluxes) in the pathway editing dialogs. There are two primary types of mass flux links: advective and diffusive, and 3 special purpose mass flux links: direct transfer, precipitate removal, and treatment.
For most applications, mass transfer between pathways can be represented as a combination of advective and diffusive processes. In some specialized cases (e.g., uptake of contaminants by plants, removal due to treatment processes), however, it may be necessary to utilize one of the three special purpose flux links to properly represent the kinetics of the mass transfer.
Advective mass flux links (as well as the three special purpose mass flux links) are created from the Inflows and Outflows tabs, which are nearly identical in appearance. The Outflows tab is used to create an advective (or special purpose flux link) from the current pathway to another pathway. The Inflows tab is used to create an advective flux link (or special purpose flux link) to the current pathway from another pathway.
The Outflows tab looks like this:
For each advective mass flux link A mass flux link in which a quantity of a medium is specified to flow from one pathway to another, carrying dissolved, sorbed, and/or suspended species with it., you must specify the pathway to which you are connecting, the medium that is flowing, and the flow rate.
You can create as many advective (and special purpose) outflows (or inflows) as desired in order to build your pathway network. Note that advective and special purpose mass flux links are unidirectional (the flow rate cannot be negative).
Diffusive mass flux links are created from the Diffusive Fluxes tab. Whereas advective fluxes can be defined between all types of pathways, all diffusive fluxes must originate in 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)..
The Diffusive Fluxes tab looks like this:
For each diffusive flux link, you must specify the pathway to which you are connecting, the Fluid through which the species are diffusing, and the properties of the diffusive link. The properties of the diffusive link include the geometry of the link and whether the diffusion takes place through a porous medium.
Unlike advective mass flux links, diffusive mass fluxes can be bi-directional. That is, species can be transported in either direction.
Although in most cases, the mass flux between two pathways will be dominated by either advection (e.g., advection in flowing water) or diffusion (e.g., diffusion through stagnant water), in some situations it will be appropriate for pathways to be simultaneously connected by both advective and diffusive links (e.g., advection and diffusion in slowly flowing water).
The assumptions and mathematical details upon which the transport pathway Physical components or compartments through which contaminant species can move and/or be stored, such as aquifers, lakes, sediments, surface soil and the atmosphere. GoldSim provides four different elements for simulating pathways. elements (and mass flux links between them) are based are
described in