Doctor of Philosophy (PhD), Wright State University, 2010, Environmental Sciences PhD
Chlorinated aliphatic hydrocarbons (CAHs) are often found as groundwater contaminants because of past industrial activities and disposal practices. CAHs pose a threat to human health and thus, create a need to find both natural and engineered processes that can remove these chlorinated compounds from the environment. Natural attenuation by oxidative biodegradation is especially important because it can allow for mineralization to carbon dioxide, a nontoxic end-product. The goal of this research was to evaluate the potential oxidative biodegradation of CAHs by microorganisms that are naturally associated with wetland plant roots. The research was divided into field work and laboratory batch studies.
The field work consisted of using newly designed pore water samplers to provide a biogeochemical characterization of a constructed wetland environment with an emphasis on the shallow vegetated zone. Reducing conditions were found at the bottom of the wetland with overlapping zones of nitrate, iron, and sulfate reduction and methanogenesis. More oxidizing conditions were found closer to the surface and in the root zone. There was evidence of tetrachloroethene (PCE) degradation by its removal and formation of daughter products, trichloroethene (TCE) and vinyl chloride (VC), both of which disappeared by possible oxidative processes in the near surface environment and root zone.
The laboratory work was done using a unique approach with microcosms containing soil-free washed wetland plant roots. The activity and TCE degradation potential by aerobic methane- and ammonia-oxidizing microorganisms naturally associated with Carex comosa roots was investigated. Methane oxidation developed faster than ammonia oxidation during the respective enrichment periods. After enrichment, methane oxidizers were able to degrade TCE in contrast to ammonia oxidizers, which were rapidly and completely inhibited, perhaps due to the presence of TCE or TCE degradation products. The root morphology, (open full item for complete abstract)
Committee: Abinash Agrawal PhD (Advisor); Don Cipollini PhD (Committee Member); Songlin Cheng PhD (Committee Member); Mark Goltz PhD (Committee Member); Patrick Megonigal PhD (Committee Member)
Subjects: Biogeochemistry; Environmental Science