Chemicals that are released into the environment are subject to transport (bioconcentration, leaching, volatilization) and degradation (biodegradation, photolysis, hydrolysis, oxidation) processes. The transport processes have a tendency to distribute and dilute or concentrate, but not destroy, the contaminant. On the other hand, chemical and biological reactions in the environment result in alterations and, frequently, degradation of the material to innocuous substances. Of the degradation processes, biological degradation of

organic compounds is the most desirable because it results generally in end-products that have been completely mineralized to inorganic compounds.