Mass-Concentration BC
Unit: [M/L3]
A mass-concentration boundary condition applies a predefined concentration to a node. Instead of calculating concentration as a simulation result, at these nodes the concentration is given by the boundary condition value. This can lead to an inflow of mass into the model when neighboring nodes have a lower concentration, or to an outflow from the model when there is a concentration gradient from the neighboring nodes towards the boundary condition.
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Using mass-concentration boundary conditions, the mass budget of the model should be checked thoroughly. In cases where fixed concentration boundaries are put into a freshwater flow, the total mass going into groundwater is easily overestimated in comparison to the original contamination source, e.g., because the source is not consistently active, or is only leaking with a limited rate. |
