Collaborative Research: Managing oxygen demand in lakes and reservoirs - a competition between natural and artificial forcing

摘要富营养化、分层水体中的氧耗尽是一个重要的全球性问题，它对饮用水处理和冷水渔业产生了负面影响。越来越多地使用气泡羽流充氧来实现缓解。虽然气泡羽流是成功地添加氧气，增加的能量可能会导致大规模的混合，这改变了水库的热结构，增加沉积物的需氧量，并改变其他沉积物-水的地球化学通量（磷，铁，锰，硫化氢和甲烷）。最近的研究表明，hypolimnetic需氧量与充气湖泊中的气体流速和整个沉积物-水界面的扩散大大增强了由假潮电流产生的湍流发作。然而，不存在模型来预测在横流中由气泡羽流引起的电流，或者将沉积物-水界面处的湍流扩散与海底边界层上方的流体速度相关联。由于需要这两种工具来开发含氧或通气储层中氧动力学的综合模型，因此该项目的目的是阐明自然强迫（例如，流入和假潮）和人工强迫（例如，气泡羽流）影响湖泊和水库中的需氧量。 这一目标将通过实验室实验和三个不同水体的实地测量来实现。染料可视化和粒子图像测速将被用来映射在横流中的气泡羽流的入侵动力学。实地实验将利用电导率、温度和深度探头和声学多普勒流速剖面仪记录入侵形成和水柱动态;将利用声学多普勒流速仪以及温度和氧气微型传感器测量沉积物-水界面的微观结构。 PI将与来自西班牙和瑞士的跨国跨学科团队合作，并将实现三个主要目标：（1）基于双羽流积分模式方法，建立了一个用于层结和横流中羽流混合的综合近场模式，（2）通过采用膜更新理论的模型，制定由于水流和湍流混合而导致的穿过下湖界面的氧通量的模型，（3）将烟羽和需氧量模型与三维水动力学模型相结合，并使用完整的实验室和现场规模数据集进行验证。 主要的智力价值将是为可变横流中的气泡羽流建立第一个科学上严格的模型，其中包括气泡和水之间的氧气转移，以及根据环境水流和湍流制定沉积物-水界面处氧气通量的机械模型。作为研究的一个组成部分，将在三个形态不同的湖泊进行实地实验，提供丰富的数据档案，描述不同气泡羽流的入侵形成，在浅水层中的大量氧气需求，以及底栖混合。为这三个组成部分（近场羽流混合、温跃层混合和海底边界层氧通量）开发的模型缩小了开发能够预测湖泊和水库的浅水层氧动态的综合数值湖泊模型所需的差距。随着美国正在考虑的几个数百万美元的气泡羽流扩散器装置，耦合3D湖泊模型的可用性在设计期间将是有价值的。 拟议活动的主要广泛影响将是完成湖泊数值模型，该模型将能够模拟各种各样的湖泊氧气动态。 该项目利用了一个多国跨学科研究人员团队的专业知识和资源，这些研究人员是湖沼学以及湖泊和水库管理的领导者。这项研究的结果将通过国际水协会湖泊和水库管理专家组在一个国际论坛上传播给研究人员和管理人员，该专家组由共同主要研究者担任主席。 作为拟议活动的一个组成部分，将制定一个创新计划，指导研究生，因为他们开发的技能，管理大型项目和监督本科生。

AbstractDepletion of oxygen in eutrophic, stratified waterbodies is a significant global problem, which negatively affects drinking-water treatment and cold-water fisheries. Mitigation is increasingly accomplished using oxygenation with bubble plumes. While bubble plumes are successful at adding oxygen, the added energy may induce large-scale mixing, which alters the thermal structure of the reservoir, increases sediment oxygen demand, and changes other sediment-water biogeochemical fluxes (phosphorus, iron, manganese, hydrogen sulfide, and methane). Recent studies of hypolimnetic oxygen demand have shown that oxygen is correlated with the gas flow rate in aerated lakes and that diffusion across the sediment-water interface is greatly enhanced by turbulent episodes generated by seiche currents. Yet, no models exist to predict the currents induced by bubble plumes in crossflow or to relate the turbulent diffusion at the sediment-water interface to the bulk fluid velocity above the benthic boundary layer. Because both of these tools are needed to develop comprehensive models of oxygen dynamics in oxygenated or aerated reservoirs, the purpose of this project is to elucidate the physical mechanisms by which currents resulting from both natural forcing (e.g., inflows and seiches) and artificial forcing (e.g., bubble plumes) affect oxygen demand in lakes and reservoirs. This goal will be realized through laboratory experiments and field measurements in three different waterbodies. Dye visualization and particle image velocimetry will be used to map the intrusion dynamics for bubble plumes in crossflow. Field experiments will document the intrusion formation and water column dynamics using profiles from conductivity, temperature, and depth (CTD) probes and acoustic Doppler current profilers (ADCP); microstructure at the sediment-water interface will be measured using acoustic Doppler velocimetry (ADV) and temperature and oxygen microsensors. The PIs will collaborate with a multinational, interdisciplinary team of colleagues from Spain and Switzerland and will pursue three primary objectives: (1) to develop a comprehensive near-field model for plume mixing in stratification and crossflow based on the double-plume integral model approach, (2) to formulate models for oxygen flux across hypolimnetic interfaces due to currents and turbulent mixing by adapting models from film renewal theory, and (3) to integrate the plume and oxygen demand models with a 3D hydrodynamic model, validated using the complete laboratory and field-scale data sets. The primary intellectual merit will be development of the first scientifically rigorous model for bubble plumes in variable crossflow that includes oxygen transfer between bubbles and water and the formulation of mechanistic models for the flux of oxygen at the sediment-water interface based on ambient currents and turbulence. As an integral part of the research, field experiments will be conducted in three morphologically different lakes, providing a rich archive of data characterizing the intrusion formation from different bubble plumes, the bulk oxygen demand in the hypolimnion, and the benthic mixing. Models developed for these three components (near-field plume mixing, thermocline mixing, and benthic boundary layer oxygen flux) close the gap necessary to develop a comprehensive numerical lake model capable of predicting oxygen dynamics in the hypolimnion of lakes and reservoirs. With several multi-million dollar bubble-plume diffuser installations being considered in the United States, the availability of the coupled 3D lake model will be valuable during design. The primary broader impact of the proposed activities will be the completed numerical lake model, which will be capable of simulating a wide range of lake oxygen dynamics. The project leverages the expertise and resources of a multinational, interdisciplinary team of researchers who are leaders in limnology and lake and reservoir management. The results of this research will be disseminated to researchers and managers in an international forum through the International Water Association Specialist Group on Lake and Reservoir Management chaired by the co-PI. As an integral part of the proposed activities, an innovative program will be developed to mentor graduate students as they develop skills to manage large projects and supervise undergraduates.