Volatilization, mixing, diffusion and sorption are considered non-destructive since no net loss of contaminant mass occurs. This section will focus on the biodegradation mechanism. However, the other mechanisms should be evaluated to help determine if biodegradation is the predominant mechanism at the site. The rate of oxygen depletion due to microbial metabolism usually exceeds the rate oxygen is replenished to the system. This will typically occur within the core of the plume, forcing anaerobic biodegradation to dominate.
Anaerobic systems are slower than aerobic systems.
When the oxygen is depleted, an alternative electron acceptor and a microorganism capable of utilizing the alternative electron acceptor must be available for biodegradation to proceed. Anaerobic systems have been shown to effectively reduce toluene concentrations in the field. Degradation of BTEX under conditions of partially depleted oxygen may be possible, but has not been demonstrated. Evaluation of Site Factors 1. Regional precipitation also needs to be considered to determine it's affect on leaching potential, oxygen and nutrient replenishment, and effect on groundwater depths.