平原区河网交汇处复杂河床下污染物迁移转化规律

The confluence zones of plain river networks are important control points of river network management in dealing with the environmental problems, such as the mixing of water pollutants, their accumulations and their transfer. The confluence zone flow always has complicated flow structure as a result of its intense turbulence, special bed morphology and unknown interaction mechanism of the pollutants between overly water and pore water. Meanwhile, the sediments in the plains are relatively fine and rich of cohesive sediment, which have strong effect of adsorption/desorption of the pollutants and play an important role in the pollutant accumulations as well as secondary pollution in water body. Research on the pollutants transfer and transformations in the complex bed morphology of confluence channels is of great value in indentifying the trail and destination of river network pollutants along with controlling pollutants in river networks. Nowadays, the relative researches mainly focus on the pollutant transfer in overly water, but the researches on the interaction and transformation of pollutants in sediment-water interface under complex bed morphology (deep hole and bar) are much fewer. In this project, laboratory experiments, numerical simulations and theoretical analysis are to be combined to study the pollutants transfer and transformations mechanism in overly water under complex bed morphology of confluence channels, the relation between sediment-water interface interaction and pore water pollutants’ movement, aiming to reveal the nature of pollutants transfer and transformation pattern in confluence zone. The research finding will enrich and complete the river network pollutants transfer theoretical system and provide a scientific basis to the water pollution control management.

平原区河网交汇处是河网水体污染物汇合掺混和输移富集的重要控制节点。河网交汇处水流结构复杂、紊动强烈，床面形态特殊，污染物河床界面交换机制未明；同时，平原地区泥沙较细且富含黏沙，对污染物具有较强的吸附/解吸作用，在污染物富集和水体二次污染方面扮演重要角色。研究平原区河网交汇处复杂河床下污染物迁移转化规律对明确河网污染物输移轨迹和归宿、治理河网水污染具有重要的意义。目前国内外研究更多关注污染物在河网地表水的迁移，很少考虑交汇处复杂河床（深坑-沙垄典型床面）引起的潜流交换以及泥沙的吸附/解吸作用。本项目采用室内实验、数值计算、理论分析相结合的方法，研究河网交汇处复杂河床下污染物在上覆水的迁移机理、在河床界面的潜流交换机制以及在河床中的迁移转化规律。成果将丰富和完善河流污染物输运理论体系，为平原区河网水污染控制和治理提供科学的依据。

平原区河网交汇处是河网水体污染物汇合掺混和输移富集的重要控制节点。河网交汇处水流结构复杂、紊动强烈，床面形态特殊，污染物河床界面交换机制未明；同时，平原地区泥沙较细且富含黏沙，对污染物具有较强的吸附/解吸作用，在污染物富集和水体二次污染方面扮演重要角色。研究平原区河网交汇处复杂河床下污染物迁移转化规律对明确河网污染物输移轨迹和归宿、治理河网水污染具有重要的意义。通过室内精细实验和现场观测研究平原区河网交汇处复杂河床下污染物迁移转化规律，主要结果如下：（1）揭示了交汇处剪切层倾斜对水位以及水流拟序结构的作用机理，发明了交汇处行洪平稳过渡导流系统，该系统可以大幅度降低交汇口水位；（2）提出了螺旋流是汇流口深坑的主要成因，推翻了前人关于剪切层高速强紊是成因的猜测；（3）利用汇流河道循环水槽开展不同交汇形态和不同典型床面形态下污染物迁移转化试验，建立以水流、泥沙污染物等为模拟要素的河网交汇处污染物输移转化数学模型，揭示上覆水中污染物输移规律；（4）研究了水动力对粘沙吸附污染物的作用机理，揭示了水流剪切力破坏粘沙团聚结构是其影响粘沙吸附污染物的重要因素；（5）利用精细水槽试验，揭示河网交汇处复杂水动力条件下污染物富集规律、以及汇流比的影响。（6）开展淮河流域典型河网交汇处污染物输移规律的现场观测，发现泥沙粒径和水中污染物浓度是底泥中污染物分布的控制因素，同时深坑处向下水流引起的潜流交换是污染物富集的重要因素。发表论文9篇，其中SCI论文8篇（第一作者3篇，通讯2篇），申请国际专利1项，授权/申请中国专利5项。项目资助期间，项目负责人入选“江苏省科协青年科技人才托举工程”培养对象、河海大学“大禹学者”计划培养对象。参编《模型试验水沙测量仪器数据交互通用规约》等学会标准2部。2017年获江苏省科学技术一等奖和大禹水利科技二等奖各1项。