Subsurface Carbon Cycling in Bioremediation of Acid Mine Drainage: Experiments and Modeling

该奖项是根据2009年《美国复苏和再投资法案》(公共法律111-5)资助的。银酸矿山排水(AMD)是一个严重的环境问题，由铁氧化细菌(IOB)介导的硫化岩石中的氧化反应引起。这项建议的主要目标是对黄铁矿氧化循环和碳循环中涉及的耦合生物地球化学过程有一个基本的定量了解，以促进评估和设计可持续的修复过程。这项拟议的工作是先前资助的使用有机碳添加剂缓解AMD的小规模研究的后续工作，该研究表明，在产酸岩石中添加有机碳可以刺激异养微生物的生长，消耗氧气和隔离铁，从而抑制黄铁矿的氧化。这项拟议的研究结合了一系列尺度上的实验和模拟，包括以下主要任务：(1)监测AMD在模拟环境条件下的生成和抑制反应，以确定矿物和有机碳从间隙孔隙到废石堆尺度的储存和运输。(2)开发用于计算模型的废石中微生物和化学动力学以及扩散速率的表达式。(3)在时间和空间尺度上表征活性有机物和矿物质在废石介质中沿流动路径的迁移和储存，以评估用于就地AMD修复的碳添加的可持续性。(4)将(1)-(3)中的理解融入到严格的反应输运模型中，并将其与废石系统中复杂的非饱和流动模型相结合，以预测废石桩和桩尺度上的行为。(5)进行敏感性分析，评价不同环境和水文条件下加碳抑制废石中AMD形成的稳健性。与目前的方法相比，该项目正在探索的就地控制AMD产生的补救策略可能会显著降低成本。此外，研究废石中的碳添加是一个机会，可以确定在现有生物地球化学系统扰动后控制地下碳循环的机制。一旦开发出多尺度模型方法，就可以用来评估其他生物修复方法的可持续性，如人工湿地和生物活性地下屏障。这项研究的多学科性质将为研究生在环境工程方面的研究和培训提供独特的机会--广泛接触水文学、地球化学、微生物学和建模。大型实验室专栏将提供针对科罗拉多州本科生、利益相关者群体和K-12学生的教育和推广机会，那里AMD对环境的影响广泛。通过科罗拉多大学环境工程专业的REU网站和夏季多元文化研究与培训(SMART)计划，将招募一批不同的本科生研究人员。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).0854510SilversteinAcid Mine Drainage (AMD) is a serious environmental problem resulting from oxidation reactions in sulfidic rock, which is mediated by iron-oxidizing bacteria (IOB). The principal objective of this proposal is to develop a fundamental quantitative understanding of the coupled biogeochemical processes involved in the pyrite oxidation cycle and the carbon cycle, facilitating the evaluation and design of a sustainable remediation process. The proposed work is a follow-up to previously-funded bench-scale studies of the use of organic carbon additions for mitigation of AMD, which demonstrated that addition of organic carbon to acid generating rock stimulates the growth of heterotrophic microorganisms, consuming oxygen and sequestering ferric iron, thus inhibiting pyrite oxidation. The proposed research, which combines experiments and modeling across a range of scales, consists of the following major tasks: (1) Monitor reactions of AMD generation and inhibition under simulated environmental conditions for sufficient duration to determine mineral and organic carbon storage and transport from the interstitial pore to waste rock pile scale. (2) Develop expressions for microbial and chemical kinetics and diffusion rates in waste rock to use in computational models. (3) Characterize transport and storage of reactive organic and mineral constituents along flow paths in waste rock media over the range of spatial and temporal scales, to evaluate the sustainability of carbon addition for in-situ AMD remediation. (4) Incorporate the understanding gained from (1) - (3) into a rigorous reactive transport model and combine it with models of complex unsaturated flow in waste rock systems to predict the behavior at the waste-rock column and pile scale. (5) Carry out sensitivity analysis to evaluate the robustness of carbon addition in inhibiting AMD formation in waste rock under a variety of environmental and hydrologic conditions. The remediation strategy being explored in this project for in-situ control of AMD generation can potentially result in significant reduction in cost compared with current approaches. Moreover, the study of carbon addition to waste rock is an opportunity to identify the mechanisms that control carbon cycling in the subsurface after perturbation of an existing biogeochemical system. Once developed, the multi-scale model approach could be used to assess sustainability of other bioremediation methods such as constructed wetlands and bioreactive subsurface barriers. The multi-disciplinary nature of the research will provide unique opportunities for graduate student research and training in environmental engineering - with broad exposure to hydrology, geochemistry, microbiology and modeling. Large lab columns will provide educational and outreach opportunities targeted at undergraduate students, stakeholder groups and K-12 students in Colorado, where the environmental impacts of AMD are widespread. A diverse group of undergraduate student researchers will be recruited through the University of Colorado REU site in environmental engineering and the Summer Multicultural Access to Research and Training (SMART) program.