Investigating pathways of hydrocarbon biodegradation and metal release in anaerobic environments

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The proposed research program is designed to investigate biogeochemical processes that govern biodegradation of petroleum hydrocarbons and mobility of metals under anaerobic conditions. Methanogenesis is the dominant process in most anaerobic environments. Complete understanding of this fundamental process will help devise better strategies for management of contaminated subsurface environments in Canada such as tailings ponds, submerged soils and sediments, wetlands, and aquifers. Enormous volumes of oil sands tailings are produced in northern Alberta during bitumen extraction process. Environmental issues associated with oil sands tailings include presence of organic contaminants such as hydrocarbons; emission of greenhouse gases (GHG); slow consolidation of tailings; and poor recovery of porewater from tailings ponds for re-use in the bitumen extraction process. The long term goal of my research is to discover the basic scientific knowledge necessary to provide solutions to these issues. I have discovered that ‘labile’ hydrocarbons (i.e., n-alkanes and monoaromatics) in tailings ponds biodegrade into CH4, producing GHG. However, a major portion of hydrocarbons in tailings are iso- and cyclo-alkanes that resist degradation. Recently, I have observed that certain iso-alkanes will eventually degrade under methanogenic conditions following a long acclimation period. These observations have led me to propose an investigation into the biodegradation of recalcitrant hydrocarbons (iso- and cyclo-alkanes) and their degradation pathways in oil sands tailings under methanogenic conditions. The results will advance our knowledge about the degradability of hydrocarbons in anoxic environments and allow me to expand my published kinetic model that predicts GHG emissions from tailings ponds to include new information about recalcitrant hydrocarbons, thereby refining our predictions of GHG emissions. Metal transport from tailings ponds to underlying aquifers can affect groundwater quality and can contaminate water bodies where groundwater meets the surface water such as in the Athabasca River. In addition, mobile metals/metalloids can migrate from underlying mature fine tailings into the overlying cap water in end pit lakes. I have observed that concentration of arsenic, vanadium and some transition metals in tailings porewater have increased during methanogenesis. I therefor propose a comprehensive investigation into the mechanism of metal solubilization in tailings pond porewater. I will focus my efforts on determining the different forms of metals (redox metal speciation), in both solid and liquid phases, during the microbial transformation of iron minerals throughout the process of methanogenesis . This new knowledge is essential for the assessment of the sustainability and health of end-pit lakes; a potential strategy for reclaiming tailings ponds.