河流水沙界面生源物质迁移转化过程及规律

As the economy continues to grow rapidly, degradation of water ecological environments is becoming an increasingly serious issue. The transport and transformation of biogenic elements, as key water quality factors, have attracted much attention from the research community, particularly on processes at the stream-groundwater interface. A number of studies published on Nature, Science and Nature Geoscience have pointed out that processes at the stream-groundwater interface influence significantly fluxes of biogenic elements, affecting not only the self-purification capacity of rivers but also the secondary pollution of the river system. The exchange of biogenic elements across the stream-groundwater interface is influenced by many environmental and hydrological factors under complex and not yet well understood mechanisms. Quantitative analysis of the exchange fluxes of biogenic elements is an important step in studying river pollution problems. Runoff is highly uneven in terms of temporal and spatial distributions and relatively large baseflows are supplied by groundwater.This study aims to combine field observations, laboratory experiments and numerical stimulations to examine key processes and mechanisms underlying the flux exchange across stream-groundwater interface under conditions of highly varying runoff. The transport path and interface flux of biogenic elements will be determined. A coupled numerical model will be developed to describe and quantify the physiochemical features and evolution processes at stream-groundwater interface. This research project, built on the applicant’s recent research results, will explore frontier research questions in the field and produce new theories and techniques for solving environmental issues concerning rivers, in particular, methods for determining and controlling the source and total amount of biogenic elements in a river ecosystem.

当前我国水环境问题日益严重，生源物质作为影响水质的重要因素，其在河流中的迁移转换一直倍受关注，特别是在水沙界面上。多篇发表在《Nature》、《Science》和《Nature Geoscience》的文章指出水沙界面物质交换过程影响着河流生源要素的通量演变规律，不仅决定了河流的自净能力还关系到河流的二次污染。河流-地下水界面生源物质的交换受众多环境和水动力因素的影响，过程极其复杂。该界面生源物质迁移转化过程及作用机制是治理和保护河流水环境亟待解决的关键科学问题之一。本项目将利用现场观测、物理实验和数值模拟等手段，并结合典型河流水沙输运过程、河床形态特征，深入研究水沙界面界面生源物质迁移转化过程，确定其循环路径和界面通量，建立描述其物化特征及演变过程的耦合模型。该项研究有望为解决河流环境问题提供新的理论和技术方法，尤其是在确定和控制河流生源物质的来源和总量方面。

当前我国水环境问题日益严重，生源物质作为影响水质的重要因素，其在河流中的迁移转换一直倍受关注，特别是在水沙界面上。多篇发表在《Nature》、《Science》和《Nature Geoscience》的文章指出水沙界面物质交换过程影响着河流生源要素的通量演变规律，不仅决定了河流的自净能力还关系到河流的二次污染。河流-地下水界面生源物质的交换受众多环境和水动力因素的影响，过程极其复杂。该界面生源物质迁移转化过程及作用机制是治理和保护河流水环境亟待解决的关键科学问题之一。.本项目将利用野外现场试验、室内物理实验和数值模拟等手段，取得了以下重要成果：（1）揭示了水沙界面水动力特性及物质传输规律。明确了适合于水沙界面水动力模拟的水流固体边界方法；建立了模拟细颗粒与水流相互作用的高效算法以及细颗粒与溶质协同输运的微尺度全耦合模型；揭示了不同因素下细颗粒耦合溶质在水沙界面的协同输运过程。（2）探明了胶体在河流水沙界面迁移转化过程及界面通量。对胶体运移沉积理论进行了优化；改进了处理胶体运移沉积的控制方程；率定了胶体运移方程中重要参量的值；分析了各重要参量对胶体迁移的影响规律。（3）探究了磷在河流水沙界面迁移转化过程及界面通量。通过提取淮河流域水质不平稳多周期的特征，改进了现有水质时间变异模型，分析了磷在淮河流域上下游中的分布及其对环境响应机制；探讨了水动力条件对沉积物中总磷含量的影响；研究了多因素对磷在潜流带中迁移的影响；得到了磷污染物在潜流带中迁移的基本规律（4）揭示了氮在河流水沙界面迁移转化过程及界面通量。采用贝叶斯网络，构建了不同空间尺度下流域水质对变化环境的响应模型，提出了一个耦合潜流、盐分输运以及氮转化的数值模型，有效模拟氮素在潜流带的迁移转化过程，进一步分析了淮河流域氨氮的分布及含量变化；探究了密度梯度对河床N2O的生成和消耗过程。.该项研究丰富和完善了河流生源物质迁移转化的理论，为解决河流环境问题提供新的理论和技术方法，尤其是在确定和控制河流生源物质的来源和总量方面。