Investigating carbon dynamics and process fundamentals to predict greenhouse gas emissions from tailings ponds

拟议的研究计划的目的是调查碳动力学和地球化学过程，治理温室气体（GHG）排放的尾矿池和底坑湖。甲烷生成是尾矿库中的主导过程，并且由微生物代谢夹带的有机物质驱动。对基本厌氧生物降解过程的全面了解不仅有助于预测温室气体排放，而且有助于设计更好的生物修复方法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。 阿尔伯塔在沥青提取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存在碳氢化合物等有机污染物;排放温室气体;尾矿固结缓慢;以及从尾矿池回收孔隙水用于沥青提取过程的回收率低。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。 我们的长期（1-7年）实验表明，挥发性提取溶剂中的某些碳氢化合物依次被本地尾矿微生物生物降解，从尾矿池中产生甲烷（CH 4）和其他温室气体。在产甲烷条件下，生物可降解碳氢化合物的范围扩大，使我能够改进我们的数学模型，该模型将夹带的溶剂碳氢化合物作为尾矿池温室气体排放总量的主要来源（约50-95%）。 这些观察结果使我提出了一个调查的生物降解的难降解的碳氢化合物（环烷烃），多环芳烃（PAH）和聚丙烯酰胺（PAM）和它们的代谢途径在油砂尾矿产甲烷条件下，使碳质量平衡可以用来确定碳流量更好的模型预测。尾矿中未回收的沥青是PAH的来源，PAM作为絮凝剂添加到尾矿中。我还建议全面调查铁循环及其与甲烷生成的联系，因为我们进行的初步研究，以减轻温室气体的生物降解的铁还原条件下的碳氢化合物表明，铁（FeIII）矿物提高油砂尾矿中的CH 4生产。因此，重要的是要了解铁矿物的作用，在生产或抑制甲烷。 拟议研究的结果将（1）增进我们对缺氧环境中碳氢化合物生物降解性的认识;（2）生成数据，用于精确模型预测温室气体排放和尾矿池中甲烷生成的维持，特别是在甲烷生成可引起影响尾矿池可持续性和健康的化学通量的底坑湖中;以及（3）深入了解氧化还原过程，从而制定温室气体减排战略。

The proposed research program is designed to investigate carbon dynamics and biogeochemical processes that govern greenhouse gas (GHG) emissions from tailings ponds and end-pit lakes. Methanogenesis is the dominant process and is driven by microbial metabolism of entrained organic substances in tailings ponds. Complete understanding of the fundamental anaerobic biodegradation processes will not only help predict GHG emissions but also aid in devising better bioremedial approaches to manage contaminated subsurface environments in Canada such as tailings ponds, submerged soils and sediments, wetlands, and aquifers. Enormous oil sands tailings are produced in Alberta during bitumen extraction. Environmental issues associated with oil sands tailings include presence of organic contaminants such as hydrocarbons; emission of 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. Our long-term (1-7 years) experiments revealed that certain hydrocarbons in fugitive extraction solvents were sequentially biodegraded by the indigenous tailings microbes to produce methane (CH4) and other GHG from tailings ponds. This expanded range of biodegradable hydrocarbons under methanogenic conditions allowed me to improve our mathematical model that attributed entrained solvent hydrocarbons as primary source contributing (~50-95%) to total GHG emissions from tailings ponds. These observations have led me to propose an investigation into the biodegradation of recalcitrant hydrocarbons (cycloalkanes), polycyclic aromatic hydrocarbons (PAH) and polyacrylamide (PAM) and their metabolic pathways in oil sands tailings under methanogenic conditions so that carbon mass balance could be used to determine carbon flow for better model prediction. Unrecovered bitumen in tailings is a source of PAH and PAM is added to tailings as a flocculant. I also propose to investigate comprehensively iron cycling and its connection with methanogenesis, because our preliminary study conducted to mitigate GHG by biodegrading hydrocarbons under iron-reducing conditions showed that iron (FeIII) minerals enhanced CH4 production in oil sands tailings. Therefore it is important to understand the role of iron minerals in the production or inhibition of CH4. The results from the proposed research will (1) advance our knowledge about the biodegradability of hydrocarbons in anoxic environments; (2) generate data for accurate model prediction of GHG emissions and sustenance of methanogenesis in tailings ponds and particularly in end-pit lakes where methanogenesis can induce chemical flux affecting sustainability and health of end-pit lakes; and (3) give insight into the redox process that can lead to development of GHG mitigation strategy.