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

研究碳动态和过程基本原理以预测尾矿库的温室气体排放

• 批准号: RGPIN-2020-04673
• 负责人: Siddique, Tariq
• 金额: $ 3.13万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=764532
• 关键词: Investigating; carbon; dynamics; process; fundamentals

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.

拟议的研究计划旨在研究控制尾矿库和终坑湖温室气体（GHG）排放的碳动力学和生物地球化学过程。产甲烷是主要过程，由尾矿库中夹带有机物质的微生物代谢驱动。全面了解基本的厌氧生物降解过程不仅有助于预测温室气体排放，还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，例如尾矿池、淹没土壤和沉积物、湿地和含水层。艾伯塔省在沥青开采过程中产生了大量油砂尾矿。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；尾矿固结缓慢；从尾矿库中回收孔隙水以在沥青提取过程中重新使用的情况较差。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。我们的长期（1-7年）实验表明，逃逸萃取溶剂中的某些碳氢化合物会被尾矿库中的本土微生物依次生物降解，从尾矿池中产生甲烷（CH4）和其他温室气体。产甲烷条件下可生物降解碳氢化合物范围的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归因于尾矿池温室气体总排放量的主要来源（~50-95%）。 这些观察结果促使我提议研究产甲烷条件下油砂尾矿中顽固性碳氢化合物（环烷烃）、多环芳烃（PAH）和聚丙烯酰胺（PAM）的生物降解及其代谢途径，以便碳质量平衡可用于确定碳流量以获得更好的模型预测。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。我还建议全面研究铁循环及其与产甲烷作用的联系，因为我们为通过在铁还原条件下生物降解碳氢化合物来减少温室气体而进行的初步研究表明，铁 (FeIII) 矿物提高了油砂尾矿中 CH4 的产量。因此，了解铁矿物质在 CH4 的产生或抑制中的作用非常重要。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，用于准确预测尾矿库中的温室气体排放和产甲烷作用的维持，特别是尾矿池中的产甲烷作用，其中产甲烷作用可引起影响尾矿湖可持续性和健康的化学通量； (3) 深入了解氧化还原过程，从而制定温室气体减排战略。