浅水湖泊水-土界面波流紊动作用对沉积物再悬浮的驱动机制及模型应用

Sediment resuspension induced by the turbulence from wave and current on the water-sediment interface in large shallow lakes plays an important role on the nutrient release from the sediment. However, the driving mechanisms of sediment resuspension remain unclear. This topic will be studied from the micro scale based on field and lab experiments in Lake Taihu. The objectives are to: (1) obtain the continuous and high-resolution observation data of the key parameters including spatiotemporal current, suspended solid concentration and turbulent kinetic energy parameters close to the lakebed, based on field observation platform in Lake Taihu. Sediment transformation and turbulence structure will be analyzed to obtain the driving mechanism of sediment resuspension. In addition, whether there exits the phenomenon of turbulent burst in Lake Taihu or not will be answered from the observed data. (2) conduct the lab flume experiment to study the impact of hydrodynamic process induced by the individual wave or current or the combination on the sediment resuspension with or without aquatic vegetations. The main mechanism of sediment resuspension and transportation will be addressed in different turbulent conditions. We will also compare the impact weight of current and wave on the turbulent kinetic energy and explicit the contribution of aquatic plants on the turbulence structure and sediment transportation in water-sediment interface. (3) develop a 3D numerical model of multi-fraction sediment transport under the combination of wind, wave, current and aquatic plants. The model will be applied to inverse and predict the influence of sediment dredging and aquatic plant restoration on hydrodynamics and mass transportation in Lake Taihu. The study will provide a useful tool for the decision makers to manage the watershed and control the internal pollution from the sediment in large shallow lakes.

浅水湖泊水-土界面波流紊动引起的沉积物再悬浮是湖泊内源营养盐释放的主要途径，然而其驱动机制还不是很清楚。本项目将以太湖为例，从微观尺度开展波流共同作用下浅水湖泊水-土界面紊动作用对沉积物再悬浮的驱动机制研究。具体为:(1)利用太湖野外观测平台，获取水-土界面微尺度、高时空分辨率的瞬时三维流速、悬浮物浓度和紊流混合动力参数时间序列，研究太湖野外"真实"环境中近底波流紊动特性与沉积物再悬浮沉降过程的内在联系，利用实测数据回答太湖中是否存在间歇性紊流猝发驱动沉积物再悬浮的现象；(2)在受控的实验室环境，研究不同水流、波浪及水生植物影响下床面的流速紊动特征和动力驱动机制，区分波浪和湖流对沉积物再悬浮驱动力的贡献，明确水生植物特性对动力驱动因素的影响；(3)开发风、浪、流、水生植物等多元素耦合的湖泊三维多组分悬浮物传输模型，预测太湖底泥清淤和水生植物修复等方法对沉积物再悬浮的影响。研究成果以期为湖泊内源污染控制提供支撑。

浅水湖泊水-土界面波流紊动引起的沉积物再悬浮是湖泊内源营养盐释放的主要途径，然而其驱动机制还不是很清楚。本项目将以太湖为例，从微观尺度开展波流共同作用下浅水湖泊水-土界面紊动作用对沉积物再悬浮的驱动机制研究。具体为:(1)利用太湖野外观测平台，获取水-土界面微尺度、高时空分辨率的瞬时三维流速、悬浮物浓度和紊流混合动力参数时间序列，研究太湖野外"真实"环境中近底波流紊动特性与沉积物再悬浮沉降过程的内在联系，利用实测数据回答太湖中是否存在间歇性紊流猝发驱动沉积物再悬浮的现象；(2)在受控的实验室环境，研究不同水流、波浪及水生植物影响下床面的流速紊动特征和动力驱动机制，区分波浪和湖流对沉积物再悬浮驱动力的贡献，明确水生植物特性对动力驱动因素的影响；(3)开发风、浪、流、水生植物等多元素耦合的湖泊三维多组分悬浮物传输模型，预测太湖底泥清淤和水生植物修复等方法对沉积物再悬浮的影响。基于室内水槽和野外原位观测，本研究运用精密仪器测量获取了高频同步的风场、波浪、湖流及悬浮物数据，明确了波浪和湖流共同作用下水动力特性及对沉积物运移规律，再通过微观尺度下紊流相干结构讨论沉积物再悬浮及泥沙运移的驱动机制，明确沉积物再悬浮的触发机理主要是由于近底紊流相干结构的间歇性猝发引起的，其中喷射和扫掠的大振幅猝发事件对沉积物的再悬浮具有重要作用。以上研究成果可为明确太湖内源释放量及泥沙、富营养化数学模型提供重要参数和理论支撑。