CAREER: Mass Transport in Groundwater: an Integration of Research and Experiential Education

可溶性污染物或示踪剂通过自然系统迁移，确定了不同采样地点的浓度随时间变化的曲线。通常，这些曲线显示的长尾不是平流和弥散过程所描述的。无论我们需要预测自然系统的演变还是我们供水的质量，我们都必须能够定量地预测这种尾矿行为。污染物迁移预测的可靠性依赖于对现场流动和迁移过程的良好了解；然而，水力特性的大反差、复杂连通性和极端的空间局部化与稀疏的数据相结合，限制了我们对控制现场尺度水文行为的基本过程和特性的理解。这项研究旨在帮助回答以下问题：在什么情况下，考虑到水力传导性的非均质性，浓度历史的拖尾可以用常用的平流-弥散模型来描述，而在可移动和较不可移动的孔隙域之间需要具有局部扩散的双连续模型？双连续传质已被用来解释某些环境中的复杂传输行为，但实验验证这一过程是有问题的，因为地球化学样品只代表孔隙空间的可移动成分，使得不能确定固定区域中的过程。最近，PI和他的同事们已经证明，电地球物理技术提供了一种方法，可以通过采样整个孔隙空间，而不仅仅是移动区域，来验证双连续介质传输的发生，并估计控制这些过程的参数。虽然这些结果显示利用遥感数据直接估计控制现场传质的水文参数(固定孔隙率和传质速率)是有希望的，但确定双域系统何时控制传质尚不清楚。特别是，目前还不清楚用这种方法可以实际研究传质速率(或扩散长度)和固定孔隙率的多少尺度，也不清楚运移的非均质性控制。这项研究的目的是确定1)在三个不同地质条件的野外地点，溶质是否在流动带和非流动带之间局部扩散，以及2)非均质带内和非均质带之间的质量传递过程如何影响我们对野外溶质运移的宏观看法。本研究的目的是开发一门综合的水文地球物理暑期课程，在该课程中，本科生研究人员将结合野外实验、课堂教学和数值模拟来开发和验证关于不同体制下控制运移过程的假设。这个实地夏令营将与宾夕法尼亚州立大学和暑期研究机会方案(SROP)合作的三所HBCU(传统上是黑人学院和大学)合作举办，该方案为期一个暑期，让少数群体和机构的学生在机构合作委员会的多数族裔机构进行尖端研究。

Soluble contaminants or tracers migrate through natural systems defining concentration versus time curves that vary between sample locations. Often, these curves show long tails that are not described by the processes of advection and dispersion. Whether we need to predict evolution of natural systems or the quality of our water supply, we must be able to quantitatively predict such tailing behavior. The reliability of contaminant transport predictions depends on a good understanding of in-situ flow and transport processes; however, large contrasts, complex connectivity, and extreme spatial localization of hydraulic properties combine with sparse data to limit our understanding of fundamental processes and properties controlling field-scale hydrologic behavior. This research looks to help answer the following question: Under what scenarios canlong tailing of concentration histories be described by commonly used advective-dispersive models given hydraulic conductivity heterogeneity, versus the need for bicontinuum models with local diffusion between mobile and less mobile porosity domains?Bicontinuum mass transfer has been used to explain complex transport behavior in some environments, but experimental verification of this process is problematic because geochemical samples only represent the mobile component of the pore space, making determination of processes in the immobile domain impossible. Recently, the PI and colleagues have demonstrated that electrical geophysical techniques provide ameans of verifying the occurrence of bicontinuum transport and estimating the parameters which control these processes by sampling the total pore space, rather than just the mobile domain. While these results show promise for using remotely sensed data for directly estimating hydrologic parameters controlling mass transfer?immobileporosity and mass-transfer rate?in situ, determining when dual-domain systems control transport is unclear. In particular, it is not clear what scales of mass transfer rates (or diffusion lengths) and immobile porosity fractions can be practically investigated with this approach, or heterogeneity controls on transport. The objectives of this research are to determine 1) whether solutes locally diffuse between mobile and less mobile zones at three field sites of differing geology, and 2) how mass transfer processes within and between heterogeneous zones affect our macroscopic view of solute transport in the field.Tied to this research is the development of an integrated hydrogeophysics summer course, where undergraduate researchers will combine field experimentation, in-class instruction, and numerical modeling to develop and test hypotheses regarding the processes controlling transport under different regimes. This field camp will be run in collaboration with three HBCUs (Historically Black Colleges and Universities) partnered with Penn State and the Summer Research Opportunity Program (SROP), a summer-long internship that engages students from minority groups and institutions in cutting-edgeresearch at majority institutions of the Committee on Institutional Cooperation.