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

05-38011郑春苗经过多年的研究，很明显，流行的平流-弥散模型（ADM）甚至不能充分描述具有适度非均质性的介质中的溶质行为。ADM的前提是，地下水流速的变化是由于水力导电性K的非均质性造成的，假设导电性K是相关的，但其他方面是随机的。从地质学的角度来看，这个前提往往是不合理的，因为在非均质含水层中，人们期望的是连通性而不是随机性。尽管越来越多的现场证据表明，在低钾矩阵中，由连接管道控制的传质至关重要，但还没有对非adm替代模型进行系统评估。该项目的目标是研究基于传质概念的替代传输模型公式，并确定获得控制相对含水层管道和周围基质之间溶质速率限制迁移的参数值的最佳方法。将在密西西比州的宏观分散实验（MADE）场地进行一套全面的实验室实验和现场测试，以评估和对比含有连接的高钾网络的含水层中溶质输送的各种理论模型。该研究项目将解决四个重要问题：(1)在非均质河流含水层中，连接的高钾优先流通道网络的性质、几何形状和规模是什么？(2)这些流道网络（和流障）与河流沉积物的质地、结构和粒度分布有何关系？(3)如果没有具体的导管网络几何知识或模型校准知识，以前确定嵌入式网络系统传质系数值的理论关系能否在实验室和现场得到验证？(4)在包含小规模高钾网络的含水层中，溶质运移的最合适模型是什么？该模型的参数如何从现成的现场和实验室数据中获得？拟议的项目将使我们能够建立一个全面、健全的概念和建模框架，这在实践中对解释连接的高k网络的控制效果很有用。在水文地质学中，这对于准确预测污染物的迁移、地下水质量的管理以及了解自然环境中溶质的迁移和分布非常重要。这项工作与水文学的其他领域和其他科学领域有关。涉及优先路径的传输和传质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，其中高导电性网络嵌入低导电性矩阵的系统是司空见惯的。在水文学中，当三角洲和河口的地表水树突状网络与地下水相互作用时，发生了缓慢的传质机制。在植物和动物组织中，营养物质和药物的输送涉及类似的传质过程，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.