浅水水体中风生波引起底泥再悬浮致水污染机理研究

Wind-induced wave often cause large amounts of sediment to resuspend, which leads to a series of water quality problems related to sediment movement. The resuspension of sediment and the release of pollutants caused by wind are closely related to the characteristics of wind field, the hydrodynamic conditions of the water and the type of the sediment. The mechanism of sediment resuspension and the environmental effects of sediment are the key to study the water pollution caused by resuspension of sediment. The experimental research and numerical simulations will be carried out to study vertical distribution of water velocity, turbulence of water flow, pressure pulsation, resuspension sediment flux, and pollutant concentration caused by wind-induced wave. The effects of wind-induced wave hydrodynamic characteristics on sediment resuspension and pollutant release could be understand and mastered in different types of sediments. The quantitative relationship between wind field characteristics and sediment release on different spatial and temporal scales could be obtained. Then, the obtained laws could be compared and evaluated through numerical simulation and theoretical analysis. The water pollution mechanisms caused by the resuspension of sediments by wind-induced wave are the theoretical basis for the comprehensive treatment of water eutrophication and shallow water environment, it also has important application value for practical projects such as ecological restoration and reconstruction of rivers and lakes.

浅水水体中风生波往往会导致大量的底泥再悬浮，继而引起一系列与泥沙运动相关的水质问题。由风扰动产生的底泥再悬浮及污染物释放与风场特征、水体水动力学条件及底泥的结构、物质组成等因素密切相关。底泥再悬浮机制和泥沙环境效应，是研究风生波引起底泥再悬浮导致水体污染的关键。本项目拟通过实验测量和数值模拟，分析风生波引起的水流速度垂向分布、水流紊动度、压力脉动、泥沙悬浮量、水体污染物浓度等参数变化，了解和掌握风生波的水动力学特性对不同类型底泥泥沙再悬浮和污染物释放的影响，定量研究风场特性与底泥污染物在不同时空尺度上释放量的关系，并通过数值模拟和理论分析比较和评价所得到的规律。研究风生波引起底泥再悬浮污染物释放的机理，可以为浅水水体（包括浅水湖泊、水库、河网及海湾水环境等）的水污染治理提供理论基础，也对河流湖泊的生态修复和重建等实际工程有重要应用价值。

泥-水界面是湖泊的重要界面，与大多数环境和生态问题有关。不同风速条件下，风-水界面的剪应力和波浪背面的风压力共同作用引起风生波，近底水体产生与风向相反的补偿流，引起水体产生纵向的风生环流。风生波引起的环流是浅水湖泊中沉积物再悬浮和输移的直接动力来源，进而造成水体二次污染。基于水槽实验数据，分析水深（h）、特征风速（U）、吹程与相对波长（L/h）、相对波高（H/h）之间的关系，得到了风生波特征参数满足波色散关系。风生波发展较充分后，相对波高和相对波长随特征风速线性增加。沉积物再悬浮后，泥水界面附近压力随特征风速指数增加。建立上覆水体-底泥-污染物耦合力学模型，定量研究沉积物再悬浮和磷的释放。基于实验测量和数值模拟，得到了风速、风生波特性、沉积物垂向分布与磷浓度之间的关系。对于不同的沉积物，沉积物解吸释放总量与风速正相关，单位沉积物解吸释放量与风速呈负相关。当沉积物在低风速或中等风速下再悬浮时，上覆水中的磷浓度迅速增加且难于扩散。磷的释放表现出小区域集中释放的特点，并迅速改变水环境。利用风速带来的水动力学条件变化，可优化生物或化学除磷方案，降低水华等环境问题的风险。