5.4 Mass Loss Expressions for Individual Loss Routes

     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 source zone, vertical leaching into the vadose zone below the source zone along with the percolating vadose zone water, wind suspension of contaminated soil particles from the soil surface, water erosion of contaminated soil particles from the soil surface, and volatilization from the soil surface (potentially through an uncontaminated layer of soil above the source zone). 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 5.56 when each loss process acts alone.