Many processes affect the fate, transport, and transformation of a particular organic chemical or compound in the subsurface. The overall composition of leachates produced reflects the degree of aerobic and anaerobic decomposition as well as retention within the soil matrix. Understanding how this material can become mobilized and what happens to it when it is mobilized is difficult and complex. Simply applying models that account for certain parameters, such as convection, dispersion, adsorption, and retardation, although commonly used is not necessarily the answer. Physical, chemical, and biological properties and processes must be considered in conjunction with site-specific environmental factors. It is often difficult to separate physical processes from chemical and biological processes because they are often coupled within any given system.