Integrated Physical and Chemical Observations of Water-rock Interactions and Coupled Matrix-conduit Flow in the Karstic Floridan Aquifer

0510054马丁智力功绩。最近人们认识到，岩溶含水层的流场包括管道、裂缝和基质的粒间孔隙，而流动的全面表征需要了解每个组成部分的流动、组成部分之间的耦合以及水如何从地表重新充入含水层。研究最多的岩溶含水层具有低粒间孔隙度，其中扩散流被限制在管道周围的细裂缝网络中。相比之下，这个建议的工作中心的Floridan含水层，它保留了高（高达20%）粒间基质孔隙度。先前关于物理水文地质学的工作（流量测量、流速温度追踪、水头观测）表明，弗洛里丹含水层的管道和基质之间的水交换是由基质和管道之间的水头梯度逆转控制的，这是由于高外源输入到管道系统中。以前的工作还没有量化的贡献fromdiffuse补给从表面，管道和矩阵之间的交换的幅度，水的停留时间，交换，或化学改性的含水层通过溶解反应。因此，本拟议项目将通过将新的化学测量与以前使用的物理观测技术相结合来确定含水层成分与水源之间的耦合。现场区域将是佛罗里达中北部的圣达菲汇/隆系统。观测将包括来自嵌套的新的和现有的威尔斯井和蒸渗仪的水的主要元素和同位素组成（土壤水采样器）用于地下水特征描述，来自河流汇、上升和岩溶窗口用于管道水特征描述，来自降水用于输入源特征描述。化学测量将提供流速与管道和基质之间的水头梯度以及碳酸盐和硅酸盐矿物的饱和状态进行比较。嵌套的威尔斯井和降水化学成分的数据将允许表征水化学的垂直差异，以确定地表扩散补给的幅度。这些数据将与其他低粒间孔隙度的岩溶含水层进行比较，使用现有的确定性模型，如化学分离。还将进行比较的结果，以前和正在进行的其他地区的弗洛里丹含水层的研究。由于Floridan含水层的高渗透性，预计粒间孔隙度成分将在含水层的整体流场中发挥重要作用。这项工作应该提高对岩溶含水层的理解和管理，这些含水层的大部分流量都在基质孔隙中。这些含水层通常代表主要的水资源，但以前一直使用概念模型进行管理，这些模型认为主要通过管道流动或将系统视为等效的多孔介质。特别是，这些成果将直接适用于佛罗里达州含水层的管理和结果将传播到关键的水管理人员通过马丁在佛罗里达州斯普林斯工作队的参与。人力资源将通过研究生和本科生教育受到影响，无论是作为目前教授的课程的正式资源，还是通过研究生论文。一个二年级的博士生目前正在研究这个主题作为他的论文的一部分，两个硕士生和几个本科生将参与现场，实验室和分析工作。

0510054MartinIntellectual Merit. It has been recognized recently that the flow field of karstaquifers includes conduits, fractures, and intergranular porosity of the matrix and that fullcharacterization of flow requires understanding flow in each component, couplingbetween the components, and how water recharges to the aquifer from the surface. Mostwell-studied karst aquifers have low intergranular porosity where diffuse flow is confinedto a network of fine fractures surrounding conduits. In contrast, this proposed workcenters on the Floridan aquifer, which retains high (up to ~20%) intergranular matrixporosity. Previous work on physical hydrogeology (discharge measurements,temperature tracing of flow rates, observations of hydraulic head), suggests that waterexchanged between conduits and the matrix of the Floridan aquifer is controlled byreversals in head gradients between the matrix and conduits as a result of high allogenicinput into the conduit system. The previous work has not quantified contributions fromdiffuse recharge from the surface, the magnitude of exchange between the conduits andmatrix, the residence time of water that exchanges, or chemical modifications of theaquifer through dissolution reactions. Consequently, this proposed project will determinecoupling between aquifer components and water sources by integrating new chemicalmeasurements with previously used physical observational techniques.The field area will be the Santa Fe Sink/Rise system in north-central Florida.Observations to be made will include major element and isotope compositions of waterfrom nested new and existing wells and lysimeters (soil water samplers) for ground watercharacterization, from the River Sink, Rise, and karst windows for characterization ofconduit water, and from precipitation for characterization of the input sources. Thechemical measurements will provide flow velocities to be compared with head gradientsbetween the conduits and the matrix and saturation states with respect to carbonate andsilicate minerals. The nested wells and data on chemical composition of precipitationwill allow characterization of vertical differences in water chemistry to determinemagnitudes of diffuse recharge from the surface. These data will be compared to otherkarst aquifers with low intergranular porosity using available deterministic models suchas chemograph separation. Comparisons will also be made to results of previous and ongoingstudies of other regions of the Floridan aquifer. Because of the highertransmissivity of the highly porous Floridan aquifer, it is anticipated that the intergranularporosity component will play a large role in the overall flow field of the aquifer.Broader Impacts. This work should improve the understanding andmanagement of karst aquifers that have significant portions of their flow within matrixporosity. These aquifers commonly represent major water resources, but have previouslybeen managed using conceptual models that consider either flow primarily throughconduits or treat the system as an equivalent porous medium. In particular, these resultswill be directly applicable to management of the Floridan aquifer and results will bedisseminated to critical water managers through Martin's participation in the FloridaSprings Task Force. Human resources will be impacted through graduate andundergraduate education, both formally as a resource for currently taught courses andthrough graduate student theses. One second-year PhD student is currently working onthis topic as part of his dissertation, and two masters students and several undergraduateswill participate in the field, laboratory, and analytical work.