4.1 Mass Loss Expressions for Individual or Multiple Concurrent Loss Pathways

The processes that can cause contaminant mass (or activity) to be lost from the source zone are assumed to be first-order radioactive decay/degradation within the pond, vertical leaching into the vadose zone below the pond, runoff from the top of the pond to the overland flow pathway, and volatilization from the surface of the pond.  Hence the overall instantaneous rate of change of contaminant mass in the source zone for contaminant i is given by



This section discusses the theory developed to describe the individual terms on the right-hand side of Equation 4.4.