Date of Award


Degree Type


Degree Name



Great Lakes Institute for Environmental Research

First Advisor

Weisener, Christopher


biodegradation; bioremediation; environmental bacteria; gamma irradiation; naphthenic acids; oil sands tailings




Open-pit mining of the Athabasca oil sands has generated large volumes of waste termed fluid fine tailings (FFT), stored in tailings ponds to promote water recycling and densification of solids. Of great concern with these ponds is accumulation of toxic organic substances, including naphthenic acids. Gamma irradiation (GI) is a possible treatment that could accelerate biodegradation of these compounds. This research investigates the response of the FFT microbial consortia to this treatment with emphasis on changes in diversity and species related stimulus. Samples were collected over 52 weeks from two representative gamma-treated FFT sources. Over this period, significant differences in microbial development were observed in the gamma-treated FFT materials in oxic and anoxic conditions. The representative anaerobic metabolizers in both ponds were dominantly chemoorganotrophic organisms. Pond 1A (P1A) FFT experienced significant (p<0.05) stimulus of organisms with biodegradation potential (e.g. Pseudomonas, Enterobacter, Diaphorobacter) and syntrophic methylotrophic capabilities (e.g. Syntrophus, Smithella). In comparison, GI treatment of FFT from South Tailings Pond (STP) did not exhibit the same impact. In this case Desulfuromonas was the principle genus showing significant (p<0.05) stimulus at the end of 52 weeks. Under atmospheric conditions (e.g. aerobic) gamma-treated FFTP1A showed an increase in organisms capable of sulfur and metal cycling (e.g. Geobacter). No significant community stimulus was observed in the gamma-treated FFTSTP under aerobic conditions. This research provides enhanced understanding of oil sands tailings biogeochemistry and GI impacts on microorganisms with the ultimate goal of accelerated stabilization and remediation toward a sustainable ecosystem.