Date of Award

5-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Environmental Engineering and Science

Committee Member

Dr. Kevin Finneran, Committee Co-chair

Committee Member

Dr. David Freedman, Committee Co-chair

Committee Member

Dr. Harry D. Kurtz, Jr.

Abstract

The Deepwater Horizon explosion and seafloor well blow out was the largest accidental oil spill in history. An estimated 206 million gallons of oil were released over the span of almost three months before it was successfully capped. In response, an oil dispersant called COREXIT was controversially applied in hopes of dissolving the massive quantities of oil, spreading it out within the water column, and avoiding accumulation on beaches. COREXIT is a mixture of cosolvents and surfactants that increases the solubility of oil in water. It was applied in large quantities, although information on the fate of specific compounds in COREXIT was limited. The goal of this research was to evaluate one of these components, propylene glycol, in regard to how it biodegrades in estuarine environments, where it is likely that conditions are anoxic. Enrichments were inoculated with sediment material from Bay Jimmy, Louisiana, an area heavily impacted by the Deepwater Horizon oil spill. Propylene glycol was quantified by gas chromatographic analysis with a flame ionization detector (GC-FID), following solid phase extraction and elution with dichloromethane and methanol. Propylene glycol degraded completely in the presence of several terminal electron acceptors, including oxygen, nitrate, sulfate, and iron (III). Oxygen, nitrate, sulfate, and iron (III) electron accepting processes did not appear to be the sole pathways of propylene glycol degradation, as rates of biodegradation were similar across all amendments. Based on this, fermentation of propylene glycol was suspected, and experiments were consequently performed to quantify organic acid as fermentation products. Additionally, DNA was isolated, amplified, and sequenced to elucidate the types of microbes present in enrichment cultures. Organic acids detected were propionate, formate, and glycolate. However, their presence did not add up to total propylene glycol degradation. Based on that and the results from the Illumina DNA sequencing, it is hypothesized that the pathway is a mixed one, where the propylene glycol is fermented, and fermentation products are oxidized using terminal electron accepting pathways. The results from these experiments provide insight into the adaptability of microbial communities. They can be applied not only to the aftermath of oil dispersant application, but also to the runoff of airplane deicing fluid into natural water bodies because propylene glycol is a major component of that as well.

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