沉水植被影响下的湖泊水流研究和污染物弥散参数化表征

The hydrodynamics in lakes is complex, which affects the transport of nutrients in lakes. In order to grasp the environmental and ecological effects of aquatic vegetation in lakes and deepen the understanding of the mechanism of water quality change, it is necessary to clarify the influence mechanism of aquatic vegetation on the water flow structure and material transport in shallow lakes. Taking water flow and pollutant dispersion in representative submerged vegetation area of Lake Taihu as the object, the vertical structure of the flow field and the dispersion characteristics of pollutant transport with submerged vegetation under different water conditions are studied by means of contrast observation techniques of in situ plant stress measurement, fixed point velocity, water quality monitoring, combined with theoretical methods and statistical analysis in this project. The vertical structure of flow with submerged vegetation is analyzed by mutual verification of vegetation resistance model and flow structure analysis method using the measured values of vegetation stress and flow velocity. The dispersion coefficient of pollutants is calculated by the model using velocity of flow and verified by the measured value. Multiple regression analysis is used to establish the quantitative relationship between the vertical structure of water flow, the dispersion coefficient of pollutants and plant characteristics (type, height, density and vegetation area), which reveals the influence mechanism of submerged vegetation on the flow structure and the transport of conserved substances in shallow lakes, which can provide scientific references for expounding the formation mechanism of water quality in vegetation areas of lakes.

湖泊中水体动力因素复杂，影响着湖泊营养盐的迁移输运。为掌握湖泊水生植被的环境和生态效应，深化对湖泊水质变化机理的认识，必须明确水生植被对浅水湖泊水流结构和物质输移的影响机制。本项目以太湖代表性沉水植被区水流和污染物弥散为对象，通过原位植物受力测定、定点流速、水质监测等原位对照观测手段，结合理论方法和统计分析，开展沉水植被影响下不同水情工况下流场垂向结构和污染物输移弥散变化特征研究。利用植被受力和流速实测值对植被阻力模型和水流结构分析方法进行相互验证率定，分析沉水植被水流垂向结构；利用流速根据模型计算污染物弥散系数，根据实测值对其进行验证；并采用多元回归分析方法建立水流垂向结构和污染物弥散系数与植物特性（类型、高度、密度和植被面积）的定量关系，揭示沉水植被对浅水湖泊水流结构和保守物质输移弥散的影响机理，为阐明湖泊植被区水质形成机制提供科学参考。

研究湖泊水流结构和污染物随湖流输移扩散规律一直是湖泊水质变化机理的重要研究内容，对湖泊水污染治理和水环境管理具有重要的现实意义。明确水生植被对浅水湖泊水流结构、物质输移以及营养盐分布的影响机制，对加强对湖泊水生植被的环境和生态效应认识有重要意义。本项目通过对湖泊水文气象和水质水生态等历史资料的分析，结合现场调查、试验进行理论分析建模。升级完善了具有自主知识产权的水生植物受力与韧性原位监测装备，实现了不同种类水生植物在不同水层深度、不同风浪和水流状况下植物的受力监测。开展了三维水动力富营养化模型——EcoLake模型在太湖的移植完善，利用现有数据率定了模型水动力、水质和水生态等关键参数并验证了模型精度。基于太湖水动力水质水生态模型，分析了关键参数对湖泊水动力、水质和水生态的影响，有利于加强对不同污染物指标关键参数贡献率的认识。开展了湖泊不同水情下水流垂向结构研究和水生植被恢复对湖区的环境效益和水质目标可达性研究，揭示太湖水流结构和水生植被区污染物空间分布差异的动力机制，为太湖污染物削减和生态修复提供理论依据和技术参数。研究了湖泊自净系数，建立了湖泊不同时段不同水情下湖泊水环境容量计算和允许污染负荷入湖河口断面分配的方法，为浅水湖泊流域污染物综合减排、水质目标管理和水环境污染综合管控提供重要参考。