Cell Pathway Example 1: Equilibrium Partitioning and Decay

Cell Pathway elements can be used simulate partitioning between the liquid and solid media as well as nuclear decay of species. In this example, a closed pond system composed of water and sediment is simulated. The system is closed because there is no in flow or out flow and water volume is fixed as is sediment mass. The simulation starts out with 10 g of species A and no amount of B in the pond and then the process of nuclear decay acts to reduce the mass of Species A (i.e. only Species A can decay) over time. The process of equilibrium partitioning also acts to always keep the mass of both Species partitioned between the media according to the specified equilibrium partitioning rate (e.g. specified in m3/kg).

10 g of species A and B are initially in the Pond system.

GoldSim calculates mass transport so it determines the Species mass in the Cell Pathway. Concentration is then derived as the Species mass / volume for fluid and Species mass / mass for solids.

Species A decays so the total mass in the closed pond system decreases over time. Species B does not decay so its total mass is constant.

Species A decays so the total mass in the closed pond system decreases over time but the partitioning ratio between water and sediment is constant. Species B does not decay so its total mass is constant and the partitioning ratio between water and sediment is constant.

Note that if this were not a closed pond system, it might not make sense to simulate equilibrium partitioning. If there is appreciable flow through the pond, then the flow rate might be large enough that you cannot assume that all of the mass immediately separates to the individual media according to the "equilibrium" ratio. In other words, if you have appreciable flow it is unlikely that there will be "time" for an equilibrium state to be reached in terms of partitioning.

To Open the Model File:

1. Start GoldSim
2. Click on the File and select Open Example...
3. Browse to General Examples --> Contaminant Transport Examples
4. Select the file called Cell1_PartitionDecay.gsm