ABSTRACT
Subsurface biotic processes include those biological phenomena that affect the transport and/or fate of compounds (organics, inorganics, or the microbes themselves) in the subsurface. One example of a subsurface biotic process is the biodegradation of an organic compound by subsurface microbiota. This chapter focuses on gaining a fundamental understanding of the impacts of biotic processes on subsurface quality. It includes fundamentals of microbiology, subsurface microbiology, subsurface metabolic processes, modeling of subsurface biodegradation, and transport of microorganisms. A myriad of factors can serve to limit the occurrence or extent of microbial metabolism of a subsurface contaminant. The biomass growth rate has been observed to be a function of the biomass population and the concentration of a limiting nutrient. For biodegradation to occur in the subsurface, microbiota must be present. Aerobic regions will be evidenced in unconfined aquifers where the diffusion of oxygen from the vadose zone exceeds the rate of oxygen consumption in the subsurface.
