Collaborative Research: Solute Transport in Aquifers Containing Connected High-Conductivity Networks: Theory Founded on Laboratory and Field Data

电话：05-38011郑春苗。经过多年的研究，流行的平流-弥散模型(ADM)显然不能很好地描述溶质在具有适度非均质性的介质中的行为。ADM是基于这样一个前提，即地下水流速的变化是由于渗透系数K的非均质性造成的，K假定是相关的，但在其他方面是随机的。从地质学的角度来看，这一前提往往是不合理的，因为在非均质含水层中，预期的是连通性而不是随机性。尽管越来越多的现场证据表明，在低K矩阵中，由连接的管道控制的传质至关重要，但还没有对非ADM替代模型进行系统的评估。该项目的目标是研究以传质概念为基础的替代运移模型公式，并确定获得控制相对含水层管道和周围基质之间溶质限速迁移的参数值的最佳方法。将在密西西比州的宏观弥散实验(MADE)现场进行一套全面的实验室实验和现场测试，以评估和对比包含连接的高K网络的含水层中溶质运移的替代理论模型。研究项目将解决四个重要问题：(1)在非均质河流含水层中，连通的高K优先流道网络的性质、几何形状和规模是什么？(2)这种流道网络(和流动障碍)与河流沉积物的结构、结构和粒度分布有何关系？(3)在没有具体的管道网络几何知识或模型校准的情况下，以前确定嵌入式网络系统中传质系数的理论关系式能否在实验室和野外得到验证？(4)什么模型最适合描述包含小规模连接的High-K网络的含水层中的溶质运移，以及如何从现成的野外和实验室数据中获得该模型的参数？该项目将使我们能够建立一个全面的、完善的概念和建模框架，在实践中有用地考虑到连接的High-K网络的控制效果。在水文地质学中，这对于准确预测污染物运移、管理地下水质量以及了解自然环境中溶质的迁移和分布是很重要的。这项工作与水文学的其他领域和科学的其他领域有关。涉及优先路径的传输和质量传递的主题对其他学科具有重要的交叉价值，例如植物学和动物生理学，在这些学科中，嵌入较少导电基质的高导电网络系统是常见的。在水文学中，当地表水的树枝状网络与三角洲和河口的地下水相互作用时，就会产生缓慢的传质机制。在植物和动物组织中，营养物质和药物的输送涉及类似的质量传递过程，尽管规模不同。

05-38011Chunmiao Zheng. .05-37668Steven M. GorelickAfter many years of research, it is evident that the prevalent, advection-dispersion model (ADM) does not adequately describe solute behavior in media with even modest heterogeneity. The ADM is based on the premise that groundwater velocity variations are due to heterogeneity in hydraulic conductivity, K, which is assumed to be correlated but otherwise random. From a geologic perspective, this premise is often unjustified because connectedness rather than randomness is expected in heterogeneous aquifers. Although a growing body of field evidence now points to the critical importance of mass transfer controlled by connected conduits in low-K matrix, there has been no systematic evaluation of non-ADM alternative models. The goal of this project is to investigate alternative transport model formulations that are based on the mass-transfer concept, and determine the best means to obtain the parameter values controlling rate-limited migration of solutes between relative aquifer conduits and the surrounding matrix. A comprehensive set of laboratory experiments and field tests at the Macro-Dispersion Experiment (MADE) site in Mississippi will be conducted to assess and contrast alternative theoretical models of solute transport in aquifers containing connected high-K networks. The research project will address four important questions: (1) What is the nature, geometry, and scale of connected high-K preferential flow channel networks in a heterogeneous fluvial aquifer? (2) How are such flow channel networks (and flow barriers) related to the texture, structure and grain-size distribution of fluvial sediments? (3) Without specific knowledge of conduit-network geometry or model calibration, can a previous theoretical relation determining the value of the mass-transfer coefficient in the embedded network systems be verified in the laboratory and field? (4) What is the most appropriate model to represent solute transport in aquifers containing small-scale connected high-K networks, and how can the parameters for that model be obtained from readily available field and laboratory data?The proposed project will allow us to establish a comprehensive, sound conceptual and modeling framework that is useful in practice to account for the controlling effects of connected high-K networks. In hydrogeology, this is important to the accurate prediction of contaminant transport, management of groundwater quality, and understanding of the migration and distribution of solutes in natural environments. This work is relevant to other areas of hydrology and to other areas of science. The topic of transport and mass transfer involving preferential pathways has important cross-over value to other disciplines, such as botany and animal physiology where systems of highly conductive networks embedded in less conductive matrix are commonplace. In hydrology, the mechanism of slow mass transfer occurs when dendritic networks of surface water interact with groundwater in deltas and estuaries. In plant and animal tissue, delivery of nutrients and drugs involves analogous mass-transfer processes, albeit at different scales.