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的生物降解和金属的移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。完全了解这一基本过程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，如尾矿库、沉水土壤和沉积物、湿地和含水层。 阿尔伯塔省北部在沥青提炼过程中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(GHG)的排放；尾矿的缓慢固结；尾矿池的孔水回收不足，以便在沥青提取过程中重新利用。我研究的长期目标是发现为这些问题提供解决方案所需的基本科学知识。 我发现尾矿库中不稳定的碳氢化合物(即正构烷烃和单芳烃)会生物降解为甲烷，从而产生温室气体。然而，尾矿中的碳氢化合物主要是抗降解的异构烷和环烷烃。最近，我观察到某些异构烷在长时间驯化后，在产甲烷的条件下最终会降解。这些观察结果促使我提议对油砂尾矿中顽固性碳氢化合物(异构烷烃和环烷烃)的生物降解及其在产甲烷条件下的降解途径进行调查。这些结果将促进我们对碳氢化合物在缺氧环境中的降解性的了解，并使我能够扩展我发表的预测尾矿库温室气体排放的动力学模型，以包括有关顽固碳氢化合物的新信息，从而完善我们对温室气体排放的预测。 金属从尾矿库到地下含水层的运输会影响地下水质量，并会污染地下水与地表水交汇处的水体，例如阿萨巴斯卡河。此外，可移动的金属/类金属可以从下部成熟的细粒尾矿迁移到末端矿坑湖泊的上覆盖水中。我观察到，在产甲烷过程中，尾矿水中砷、钒和一些过渡金属的浓度都有所增加。为此，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。我将集中精力确定在整个产甲烷过程中铁矿物的微生物转化过程中，固态和液态中不同形态的金属(氧化还原金属形态)。这一新知识对于评估尾矿湖的可持续性和健康至关重要；这是一种潜在的尾矿池复垦战略。

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.