Freundlich or Langmuir nonlinear sorption may be considered. When nonlinear sorption is used, the program splits the layers into sublayers and uses an iterative technique to determine the equivalent linear distribution coefficient for each sublayer. This option is used to vary properties of the model with time. The user may vary the source concentration, contaminant mass, volume of leachate collected, Darcy velocity, dispersivity and aquifer velocity. For example, this option can be used to simulate the progressive failure of the leachate collection system in a landfill.
Time is divided into groups.
In each group the properties may be constant with time or may increment linearly with time. The concentration in the source at the beginning of each time group may be specified or the concentration at the end of the last group may be used. One or more passive sinks may be used in the model. A passive sink is a layer where there is a horizontal velocity. This will have the effect of removing contaminants.