ABSTRACT
Contaminants sorbed onto or into soil microbiota in either the saturated or unsaturated zone. Because only aerobic degradation is considered important for hydrocarbons, and the concentration of biota in soil drop off sharply with increasing depth, the unsaturated zone is probably much more important than the saturated zone for biodegradation of hydrocarbons. However, some groundwater does contain dissolved oxygen sufficient to allow the aerobic biodegradation of a few milligrams/liter of dissolved hydrocarbons. Biological removal of contaminant compounds from soil consists of two distinct, yet somewhat interdependent, mechanisms: microbial uptake and biodegradation. Baughman and Paris reviewed microbial uptake studies in which various bacterial species were contacted with the same compound. The precise kinetics of biodegradation would be extremely complex if all of the many combinations were considered. Enhancement of biodegradation principally attempts to increase the availability of oxygen to soil and groundwater microbes.
