Investigating pathways of hydrocarbon biodegradation and metal release in anaerobic environments

拟议的研究计划旨在研究在厌氧条件下控制石油碳氢化合物生物降解和金属流动性的生物地球化学过程。在大多数厌氧环境中，产甲烷是主要的过程。对这一基本过程的全面了解将有助于制定更好的策略来管理加拿大受污染的地下环境，如尾矿池、淹没土壤和沉积物、湿地和含水层。******在沥青提取过程中，阿尔伯塔北部产生了大量的油砂尾矿。与油砂尾矿相关的环境问题包括碳氢化合物等有机污染物的存在；温室气体排放；尾矿缓慢固结；尾矿库孔隙水在沥青提取过程中的回用回收率较差。我研究的长期目标是发现解决这些问题所需的基本科学知识。******我发现尾矿库中的“不稳定”碳氢化合物（即正构烷烃和单芳烃）可生物降解为CH4，产生温室气体。然而，尾矿中的大部分碳氢化合物是抗降解的异烷烃和环烷烃。最近，我观察到，经过长时间的驯化，某些异烷烃最终会在产甲烷条件下降解。这些观察结果使我提议对产甲烷条件下油砂尾矿中顽固性碳氢化合物（异烷烃和环烷烃）的生物降解及其降解途径进行研究。这些结果将提高我们对缺氧环境中碳氢化合物可降解性的认识，并允许我扩展我发表的预测尾矿池温室气体排放的动力学模型，以包括有关顽固性碳氢化合物的新信息，从而改进我们对温室气体排放的预测。******金属从尾矿库运输到下面的含水层会影响地下水质量，并可能污染地下水与地表水相遇的水体，如阿萨巴斯卡河。此外，流动的金属/类金属可以从下伏的成熟细尾砂中迁移到端坑湖上覆的盖水中。我观察到，在产甲烷过程中，尾矿孔隙水中砷、钒和一些过渡金属的浓度有所升高。因此，我建议对金属在尾矿库孔隙水中的增溶机理进行全面的研究。我将专注于确定在整个甲烷生成过程中，在铁矿物的微生物转化过程中，固体和液相中不同形式的金属（氧化还原金属形态）。这一新知识对于评估坑底湖的可持续性和健康至关重要；尾矿池回收的潜在策略。*****

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.*****