Defining Spatially Variable Media Properties

In many cases, you will want the properties of the environmental 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. in your model to vary spatially. For example, the solubility for a 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 Water or the partition coefficient for a species in Sand may take on different values in different locations (pathways) in your model.

The simplest way to accommodate this is to simply have pathways and Sources reference different media at different locations in your model. This approach will work well for Solids and most Fluids.

Note, however, that there can be only one 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). in your model, and like the Species element, it cannot be copied. Hence, if solubility or one of the other Reference Fluid properties varies spatially in your model (e.g., due to a change in pH along a flow path), you cannot represent this simply by copying or inserting multiple Reference Fluids in different portions of your model.

GoldSim provides two ways to vary the properties of the Reference Fluid:

1. You can create a new Fluid (by defining new Fluids with a set of Solubilities rather than a set of 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.).; or
2. You can create a clone of the Reference Fluid.

The resulting behavior of the system using these two approaches has some important differences, which are outlined in the topics below. The manner which you select will be a function of which of these two approaches best represents the actual behavior of the system you wish to simulate. In most cases, the second of the two methods discussed below would be most appropriate.