Quantifying the Role of Mixing Interfaces in Biogeochemical Cycling in a Contaminated Aquifer-Wetland System: Linking Hydrogeological, Microbiological and Geochemical Processes

0418488 McGuire量化控制氧化还原电位的耦合水文地质、微生物和地球化学过程是理解地下系统中营养物和污染物的命运和运输的基本问题，从而保护饮用水和生态系统健康。 在地下系统中，氧化还原状态的变化通常由微生物的末端电子接受过程（TEAP）的变化控制，所述末端电子接受过程（TEAP）由限制性末端电子受体（例如氧、硝酸盐或硫酸盐）的递送引发。 因此，减少的含水系统和更多的含氧“再充注”水之间的混合界面是技经评估组动态增加的区域。 尽管混合界面的重要性已得到公认，但由于难以在相关的空间和时间尺度上获得水文、地球化学和微生物测量结果，因此很少有实地调查针对这些小规模的过渡区。 这项跨学科研究旨在量化污染含水层-湿地系统内混合界面上TEAP的溶质运移、地球化学、动力学和微生物控制。 将开发高分辨率数值模型，以整合观测结果，检验关于界面对系统整体还原能力的作用的假设，了解过程并指导现场/实验室试验，并评估水文条件变化对营养物和有机污染物的命运和运输的潜在影响。 为了实现这一目标并检验核心假设，即由于提供有限的电子受体或供体，在界面处观察到最大的技经评估组动态，包括微生物活动和转化率，我们将执行以下任务：1）绘制和量化各种水文条件下技经评估组在重要混合界面上的分布; 2）在诱导混合界面进行电子受体利用率的原位动力学研究; 3）确定与水化学变化直接相关的微生物群落的原位变化;和4）使用数值模型和测试假设的混合界面区在可变水文条件下对地球化学循环的影响，整合测量控制。 我们对现有和最近开发的工具的新应用将使量化微生物群落结构和活性的小规模变化与相应的地球化学之间的复杂联系成为可能。 关于技经评估组在混合界面的控制措施的新的基本知识预计将提高我们对氧化还原敏感物种的命运和迁移的理解，包括营养物质和人为污染物，从而提高我们评估风险和保护饮用水和生态系统功能的能力。 预计这项研究的结果不仅对寻求改进方法来测量和解释复杂的耦合地球系统过程的科学家，而且对工业、监管机构和公众都具有重要价值。 为了确保这项研究的广泛影响得到广泛传播，我们制定了以下策略：1）让学生参与进来（K-12，本科生和研究生）通过直接就业，课程开发和教育培训; 2）通过研讨会，会议和同行评审的出版物吸引其他领域的研究人员; 3）通过广泛分发概况介绍、研究地点图尔斯参观和网页设计教育公众;和4）通过鼓励代表性不足的群体的参与增加多样性。

0418488McGuireQuantifying the coupled hydrogeological, microbiological, and geochemical processes that control redox potential is a fundamental issue in understanding the fate and transport of nutrients and contaminants in subsurface systems and thus in protecting drinking water and ecosystem health. In subsurface systems, changes in redox state are often controlled by shifts in the terminal electron accepting processes (TEAPs) of microorganisms, initi-ated by the delivery of limiting terminal electron acceptors such as oxygen, nitrate, or sul-fate. Thus, mixing interfaces between reduced aqueous systems and more oxic "re-charge" water, are zones of increased TEAP dynamics. Despite the well-recognized im-portance of mixing interfaces, few field investigations have targeted these small-scale, transient zones due to difficulties in obtaining hydrologic, geochemical and microbial measurements at relevant spatial and temporal scales. This interdisciplinary study seeks to quantify the solute transport, geochemical, kinetic, and microbiological controls on TEAPs at mixing interfaces within a contami-nated aquifer-wetland system. High-resolution numerical models will be developed to integrate observations, test hypotheses regarding the role of interfaces on the overall re-ducing capabilities of the system, understand processes and guide field/laboratory ex-periments, and evaluate the potential effects of changing hydrologic conditions on the fate and transport of nutrients and organic contaminants. To accomplish this and test the central hypothesis that maximum TEAP dynamics, including microbial activity and transformation rates, are observed at interfaces due to the delivery of limiting electron acceptors or donors we will perform the following tasks: 1) map and quantify the distri-bution of TEAPs across significant mixing interfaces during various hydrologic condi-tions; 2) conduct in-situ kinetic studies of electron acceptor utilization rates at induced mixing interfaces; 3) identify in-situ changes in microbial community directly related to changes in water chemistry; and 4) integrate measured controls using numerical models and test hypotheses regarding the impact of mixing-interface zones on biogeochemical cycling during variable hydrologic conditions. Our novel application of existing and re-cently developed tools will make it possible to quantify the complex linkages between small-scale changes in microbial community structure and activity and the corresponding geochemistry. New and fundamental knowledge of the controls on TEAPs at mixing in-terfaces is expected to improve our understanding of the fate and transport of redox-sensitive species including nutrients and anthropogenic contaminants and thereby im-prove our ability to assess risk and protect drinking water and ecosystem function. The findings of this research are expected to be of great value not only to scien-tists searching for improved ways to measure and interpret complex, coupled earth sys-tem processes but also to industry, regulatory agencies, and the general public. To ensure the broader impacts of this research are widely disseminated we have developed strate-gies to 1) involve students (K-12, undergraduate and graduate) through direct employ-ment, course development, and educator training; 2) attract researchers from other fields through workshops, meetings, and peer reviewed publications; 3) educate the public through widely distributed fact sheets, research site tours and web page design; and 4) increase diversity by encouraging the participation of underrepresented groups.