Flow-Induced Redox Geochemistry Within Fractured/Macroporous and Layered Vadose Zone

裂缝/大孔和层状包气带内流动诱导的氧化还原地球化学

• 批准号: 0635961
• 负责人: Binayak Mohanty
• 金额: $ 47.67万
• 依托单位: Texas A&M Engineering Experiment Station
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-05-01 至 2013-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0635961&HistoricalAwards=false
• 关键词: Flow; Induced; Redox; Geochemistry; Within

The fate and transport of reactive contaminants in variably-saturated subsurface environments is complex, involving linked hydrologic, geochemical, and microbiological processes. As water moves through the layers/lenses/fractures, it may differentially "pick-up" organic matter and inorganic ions from contact with minerals and soil structures and experiences various reduction/oxidation (redox) conditions. Although these processes are evident, measurements and conceptual modeling to quantify the importance/role of these processes have not been undertaken largely due to the inability to measure pore-scale water content/matric potential and complete geochemical suites on the small volumes of fluid available in pore water systems. In addition, unquantified evolutionary redox processes occurring across various hydrologic interfaces including atmosphere-vadose zone, soil layers/lenses, ground water-vadose zone, soil minerals-organics, and soil matrix-fractures confound the ability to predict and evaluate the success of using monitored natural attenuation to remediate a contaminated site. Using emerging pore water sampling and monitoring technologies and novel experimental designs, we propose to conduct several controlled soil column experiments with (1) soil textural layering with different hydraulic properties, (2) staggered geological lenses with different mineralogy, (3) fractures with preferential flow and transport, and (4) groundwater capillary fringe with known chemistry. Benchmark data sets from these experiments will be used to isolate and understand the contribution of various physical and chemical factors governing evolutionary transport processes of major elements including linked C, N, S, and Fe cycles. New conceptual understanding of the flow-induced redox processes will be made by corroborating data from designed experiments and loosely-coupled soil hydrologic (HYDRUS_1D) and geochemical (PHREEQC) process models. Subsequently, our new and improved conceptual and numerical models along with upscaled (bio) geochemical constitutive parameters will be applied and tested at Norman Landfill site, Oklahoma, where several previous and ongoing complementary environmental studies have been conducted. Our experiment-modeling study will provide improved knowledge necessary to more accurately predict rates of natural attenuation in any reduced site useful in petroleum and mixed contaminant systems, as in Norman landfill site in Oklahoma, and may allow for this remediation strategy to be implemented at a greater number of sites resulting in significant cost savings. Undergraduate and graduate students will be trained in the laboratory, field, and modeling studies. Concerted efforts will be made to recruit students from under-represented groups. This interdisciplinary project will enhance interaction between basic science and engineering education and will help develop improved hydrologic and biogeoscience curriculum with research emphasis. Important research findings will be disseminated to high school teachers through an ongoing NSF-supported geosciences education program Professional Learning Community Model for Alternative Pathways in Teaching Science and Mathematics (PLC-MAP) at TAMU.

在可变饱和地下环境中的活性污染物的命运和运输是复杂的，涉及相关的水文，地球化学和微生物过程。当水移动通过层/透镜体/裂缝时，它可能从与矿物质和土壤结构的接触中不同地“拾取”有机物质和无机离子，并经历各种还原/氧化（氧化还原）条件。虽然这些过程是显而易见的，测量和概念建模，以量化这些过程的重要性/作用还没有进行，主要是由于无法测量孔隙尺度的水含量/基质势和完整的地球化学套件上的小体积的流体孔隙水系统。此外，发生在各种水文界面（包括大气-包气带、土壤层/透镜体、地下水-包气带、土壤矿物-有机物和土壤基质-裂缝）上的未量化的进化氧化还原过程混淆了预测和评估的能力使用监测的自然衰减来修复受污染的场地。利用新兴的孔隙水采样和监测技术以及新颖的实验设计，我们建议进行几个受控土柱实验，包括（1）具有不同水力特性的土壤质地分层，（2）具有不同矿物学的交错地质透镜体，（3）具有优先流动和运输的裂缝，以及（4）具有已知化学性质的地下水毛细边缘。从这些实验的基准数据集将被用来隔离和了解各种物理和化学因素的贡献，包括链接的C，N，S和Fe循环的主要元素的演变运输过程。流动引起的氧化还原过程的新概念的理解，将通过从设计的实验和松散耦合的土壤水文（HYDRUS_1D）和地球化学（PHREEQC）过程模型的佐证数据。随后，我们的新的和改进的概念和数值模型沿着与放大（生物）地球化学本构参数将应用和测试在诺曼垃圾填埋场，俄克拉荷马州，在几个以前和正在进行的补充环境研究已经进行。我们的实验建模研究将提供必要的改进知识，以更准确地预测在石油和混合污染物系统中有用的任何减少网站的自然衰减率，如在俄克拉荷马州的诺曼垃圾填埋场，并可能允许在更多的网站实施这种补救策略，从而节省大量的成本。本科生和研究生将接受实验室，现场和建模研究的培训。将作出协调一致的努力，从代表性不足的群体中招收学生。这一跨学科项目将加强基础科学和工程教育之间的互动，并将有助于制定以研究为重点的改进的水文和生态科学课程。重要的研究成果将通过一个正在进行的NSF支持的地球科学教育计划传播给高中教师专业学习社区模式在教学科学和数学（PLC-MAP）的替代途径在TAMU。