Collaborative Research: Role of interfacial turbulence in hyporheic exchange and fine particle dynamics

合作研究:界面湍流在潜流交换和细颗粒动力学中的作用伊利诺伊大学厄巴纳-香槟分校为了提高我们评估水生生态系统连通性的能力，评估碳、营养物质和污染物通过河流网络的传播，有必要提高对地表水流动和潜在孔隙水之间相互作用的理解。并预测人类改变流域的净影响。在之前nsf支持的研究中，研究人员发现，水动力相互作用导致河流和底层孔隙水之间的快速交换，以及细颗粒的持续沉积和再悬浮。预计这些过程将大大影响河网中溶质和颗粒的下游迁移。不幸的是，关于控制这种行为的流体动力学机制的信息很少，因为直接测量孔隙水中的溶质和颗粒动力学非常困难。当前项目的目标是提高对自由流和孔隙水之间流体动力学相互作用的基本理解，并利用这些信息来转换河流中溶质和颗粒动力学的概念和定量模型。研究人员将使用一系列新的流动可视化技术来直接观察河流和河床之间的流体交换，以及相关的溶质和细悬浮颗粒的通量。研究结果将用于确定溶质和颗粒在多孔环境界面上传输的主要流体流动过程。这项工作将产生改进的地表-地下连续流模型，以及下游溶质和颗粒输运的新概率模型。这项工作的主要科学贡献将是改进河流和河床之间流动耦合的基本机制的表征，以及河流中溶解和悬浮物质迁移的新模型。这些模型对于预测河流系统可持续管理所需的大规模长期动态至关重要。该项目将描述目前溶质输运模型中缺失的界面通量的重要组成部分，并提供细颗粒沉积和再悬浮的关键新观测结果。需要这些信息来解决淡水系统中的许多紧迫问题，包括污染物与沉积物的相互作用、河流内生态多样性的保护、河流中的营养物质保留和碳处理以及水媒疾病传播。本项目开发的模型可用于评估产生污染物和水媒疾病传播高风险的因素，从而改善流域管理，尽量减少这些风险。该项目还将通过提高我们预测河流长期生物地球化学和生态动态的能力，促进饮用水资源和水生生态系统的长期可持续性。该项目将通过将项目成果纳入西北大学和伊利诺伊大学的主要推广工作，为更广泛的学生和公众教育做出贡献。重点将是帮助K-12学生和社区社区了解河流过程如何影响水质、人类健康和自然生态系统。调查人员还将与几个大学生团体合作，制定一个新的项目，包括定期的校园活动，并为来自科学领域代表性不足的群体的学生提供指导。总体而言，每年约有1500名K-12学生和成年人（在项目的整个生命周期中约有4500人）将参与实验室活动和讨论水文过程对可持续性的重要性。

Collaborative Research: Role of interfacial turbulence in hyporheic exchange and fine particle dynamicsAaron Packman, Northwestern UniversityJames Best, Kenneth Christensen, Marcelo Garcia University of Illinois at Urbana-ChampaignIt is essential to improve understanding of interactions between surface water flows and underlying porewaters in order to advance our ability to assess connectivity in aquatic ecosystems, evaluate the propagation of carbon, nutrients, and contaminants through river networks, and predict the net effects of human modification of watersheds. In previous NSF-supported research, the investigators found that hydrodynamic interactions caused rapid exchange between rivers and underlying porewater, along with ongoing deposition and resuspension of fine particles. These processes are expected to substantially influence downstream migration of solutes and particles in river networks. Unfortunately, very little information is available on the hydrodynamic mechanisms that control this behavior because it has been extremely difficult to directly measure solute and particle dynamics in porewaters. The objectives of the current project are to improve fundamental understanding of hydrodynamic interactions between freestream flows and porewaters, and to use the information to transform conceptual and quantitative models for solute and particle dynamics in rivers. The investigators will use an array of new flow visualization technologies to obtain direct observations of fluid exchange between rivers and streambeds, and the associated fluxes of solutes and fine suspended particles. The results will be used to identify the main fluid flow processes responsible for solute and particle transport across porous environmental interfaces. This work will yield improved models for the surface-subsurface flow continuum, as well as new probabilistic models for downstream solute and particle transport. The major scientific contributions of this work will be an improved characterization of fundamental mechanisms of flow coupling between rivers and riverbeds, and new models for the migration of dissolved and suspended materials in rivers. Such models are essential to enable the prediction of large-scale, long-term dynamics required for sustainable management of river systems. The project will characterize important components of interfacial flux currently missing from solute transport models, and provide critical new observations of fine particle deposition and resuspension. This information is needed to address many pressing problems in freshwater systems, including contaminant interactions with sediments, protection of ecological diversity within rivers, nutrient retention and carbon processing in rivers, and waterborne disease transmission. The models developed in this project can be used to evaluate the factors that produce high risks of transmission of contaminants and waterborne diseases, and thereby improve management of watersheds to minimize these risks. The project will also contribute to longer-term sustainability of drinking water resources and aquatic ecosystems by improving our capability to predict long-term biogeochemical and ecological dynamics in rivers. The project will contribute to the broader education of students and the public by incorporating project results into major outreach efforts at Northwestern University and the University of Illinois. The focus will be on helping K-12 students and neighborhood communities to understand how river processes influence water quality, human health, and natural ecosystems. The investigators will also work with several university student groups to develop a new program involving regular on-campus activities and mentoring for students from populations underrepresented in the sciences. Overall, ~1500 K-12 students and adults each year (~4,500 over the lifetime of the project) will be engaged in laboratory activities and discussions of the significance of hydrological processes to sustainability.