Understanding Advective Mass Flux Links

Advective mass flux links are used to transport mass via a flowing medium. They are defined by specifying that a quantity of medium is moving (flowing) from one location to another. Species mass which is dissolved, suspended or otherwise associated with the medium is transported with the medium as it moves. Hence, an advective mass flux is computed as the concentration of the mass in the medium multiplied by the rate at which the medium is flowing:

Advective Mass Flux = Concentration * Flow Rate

Typically, the medium is a fluid, such as water. For example, suppose that you were simulating nutrient concentrations in a lake that was fed by two streams, and which discharged to a small river. The lake and streams would be represented by pathway elements. To define the inflows to the lake, you would create two advective mass flux links (one for each stream) from the two stream pathways to the lake. You would define the outflow from the lake by creating an advective mass flux link from the lake to a pathway representing the river.

Similarly, if you were simulating the transport and fate of a drug within the body (pharmacokinetic modeling), you might create advective mass flux links between pathways representing the various organs (e.g., liver, lungs) in which the fluid being advected was blood.

Although you will typically move fluids through mass flux links, in some cases it may be appropriate for the moving medium to be a solid. For example, you could model the deposition and resuspension of sediments in a lake using advective mass flux links. Any contaminants associated with (sorbed onto) the sediments would be transported with them. The movement of soil (via erosion) and the transport of contaminants associated with the soil could also be simulated using advective mass flux links involving solids.

Note: The Contaminant Transport Module is a mass transport model, not a flow model. That is, it does not directly solve for the movement of media through the environmental system being modeled. Hence, you must directly enter the media flow rates associated with an advective flux link (or provide GoldSim with the equations for computing them).