Particle Removal and Re-suspension in the near-Field of the Columbia River Plume

哥伦比亚河羽流近场中的颗粒去除和重新悬浮

• 批准号: 0648655
• 负责人: Alexander Horner-Devine
• 金额: $ 30.05万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-04-01 至 2011-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0648655&HistoricalAwards=false
• 关键词: Particle; Removal; Re; suspension; near

OCE-0648655During the River Influences on Shelf Ecosystems (RISE) project, suspended particle concentration and size data were collected simultaneously with turbulence, velocity and density data in the near field of the Columbia River plume. This energetic region of the plume is characterized by rapid mixing, high primary productivity, significant release of particles from the plume and, ac-cording to the work described in this proposal, re-suspension and entrainment of particles from the seafloor. In this project, the corresponding sediment and turbulence data sets are used to determine whether predicted relationships between particle size and small-scale turbulent shear are observed in river plumes. These results are then extended to determine how turbulence generated by frontal processes, bottom shear and internal waves modifies the retention and removal of particles in different regions of the plume. A second goal of the proposed work is to investigate the process of sediment re-suspension and its subsequent entrainment into the plume. Observations during RISE and previous cruises suggest that a significant amount of sediment is re-suspended during energetic ebbs in the stratified region offshore of the plume lift-off point. Such processes may explain observations of increased micronutrient levels in the plume near-field relative to the ocean and estuary, and help to explain the high productivity in the plume system. The passage of the plume front, which penetrates well below the base of the plume, will be examined in detail to determine its role in re-suspending and re-entraining sediment into the plume. This work is being done in parallel with many other physical, biological and geochemical studies of the Columbia Plume that are included in the RISE project. In addition to addressing questions relating to the role of turbulent processes on particle dispersal, the proposed work will benefit from and contribute to the larger interdisciplinary study of the plume system. It will leverage work already in place to provide key information about the role of sediment in the system, which was not included in the original proposal. Intellectual merit: Particle transport is determined in large part by particle size via settling velocity. The proposed work will test relationships between particle size and turbulence in a productive river plume and relate variability in the particle field to plume processes. It will also determine the relative contributions to the plume from vertical (turbulent) and horizontal (advective) particle fluxes. Knowledge of these processes will contribute to the understanding of river-influenced ecosystems, the ability to model sediment processes in plumes, and the capability to sense suspended sediment from space.Broader impacts: The proposed research will help explain the dynamics of sediment particles in turbulent environments and thus the transport of pollution, pathogens or other particle-bound matter. The highly productive Columbia Plume also provides habitat and food to endangered salmonids. Resuspended particles enhance primary productivity by supplying micronutrients. Turbidity provides relief from predation for juvenile salmonids. The project will provide support for Emily Spahn, a graduate student in Civil and Environmental Engineering. In addition to training, it will provide support for Ms. Spahn to attend professional conferences. The project will also provide support for an undergraduate student, thus introducing a student to different aspects of physical oceanographic research. Efforts will be made to recruit a student from an underrepresented group with the assistance of the College of Engineering's Diversity and Student Services (DASS) office. Finally, the project will support an early career assistant professor.

OCE-0648655在河流对陆架生态系统的影响（RISE）项目期间，在哥伦比亚河羽流近场同时收集了悬浮颗粒浓度和尺寸数据以及湍流、速度和密度数据。羽流这一高能区的特点是混合迅速、初级生产力高、羽流释放大量颗粒，以及根据本提案所述的工作，海底颗粒的再悬浮和夹带。在这个项目中，相应的沉积物和湍流数据集被用来确定是否预测的颗粒大小和小尺度湍流切变之间的关系，观察河流羽流。这些结果，然后扩展到确定如何湍流所产生的锋面过程，底部剪切和内部波修改保留和去除的颗粒在不同区域的羽流。拟议工作的第二个目标是调查沉积物重新悬浮及其随后夹带到羽流中的过程。在上升探测器和以前的航行中进行的观测表明，在羽流升空点近海分层区域的能量退潮期间，大量沉积物重新悬浮。这种过程可以解释在相对于海洋和河口的羽流近场中微量营养素水平增加的观测结果，并有助于解释羽流系统的高生产力。将详细研究羽流前缘的通过情况，以确定其在使沉积物重新悬浮和重新夹带到羽流中方面的作用。这项工作正在与RISE项目中包括的对哥伦比亚羽流的许多其他物理、生物和地球化学研究并行进行。除了解决与湍流过程对颗粒扩散的作用有关的问题外，拟议的工作将受益于并有助于对羽流系统进行更大规模的跨学科研究。它将利用已经开展的工作，提供关于沉积物在系统中的作用的关键信息，这一信息未列入最初的提案。知识价值：颗粒输送在很大程度上取决于通过沉降速度的颗粒尺寸。拟议的工作将测试颗粒大小和湍流之间的关系，在一个生产性的河流羽流和羽流过程中的颗粒场的变化。它还将确定垂直（湍流）和水平（平流）粒子通量对羽流的相对贡献。对这些过程的了解将有助于理解受河流影响的生态系统，建立羽流沉积过程模型的能力，以及从空间感知悬浮沉积物的能力。更广泛的影响：拟议的研究将有助于解释湍流环境中沉积物颗粒的动力学，从而解释污染物、病原体或其他颗粒结合物质的迁移。高产的哥伦比亚羽也为濒危的鲑鱼提供栖息地和食物。再悬浮颗粒通过提供微量营养素提高初级生产力。海龟为幼鲑提供了捕食的救济。该项目将为土木与环境工程专业的研究生艾米丽斯班提供支持。除培训外，它还将为Spahn女士出席专业会议提供支助。该项目还将为一名本科生提供支助，从而向学生介绍物理海洋学研究的不同方面。将努力从一个代表性不足的群体招募一名学生与工程的多样性和学生服务（DASS）办公室的学院的协助。最后，该项目将支持一个早期的职业助理教授。