Fine Sediment Deposition and Filtration Under Losing and Gaining Flow Conditions: A Particle Tracking Model Approach
Fine Sediment Deposition and Filtration Under Losing and Gaining Flow Conditions: A Particle Tracking Model Approach
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DOI：
10.1029/2019wr026057
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发表时间：
2020-02
影响因子：
5.4
通讯作者：
A. Preziosi-Ribero;A. Packman;J. Escobar-Vargas;C. Phillips;L. D. Donado;S. Arnon
中科院分区：
文献类型：
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作者：
A. Preziosi-Ribero;A. Packman;J. Escobar-Vargas;C. Phillips;L. D. Donado;S. Arnon
细颗粒物在河床中的沉积通过改变潜流交换通量，对河流生态和地球化学起着重要作用。此外，它是无处不在的溪流和河流中的所有流动阶段。然而，细颗粒物沉积的动力学仍然没有完全了解河流，连续介质模型，如平流扩散方程需要修改，以准确地表示的过程。为了加强对细颗粒动力学的理解，我们开发了一种新的数值颗粒跟踪模型，模拟细颗粒沉积作为一个随机过程下失去，中性，和获得径流条件。这些流动条件通过结合自由表面和地下水流产生三种不同的速度剖面。此外，我们的模型的一个新的方面是过滤后的颗粒的存储，以估计床内的浓度场。我们的模拟结果与以前的实验室水槽实验结果的高岭石沉积在类似的条件下进行了定性比较。该模型表明，细颗粒的沉积模式和停留时间函数在很大程度上取决于流和地下水之间的交换通量，以及床过滤性能的颗粒的沉积发生在更大的深度在失去流的条件比在中性和增益的情况下。因此，颗粒沉积的空间模式是孔隙水速度分布的直接结果，而浓度取决于床内的过滤动力学。
Fine particle deposition within riverbeds plays a major role in riverine ecology and biogeochemistry by altering hyporheic exchange flux. Moreover, it is ubiquitous within streams and rivers across all flow stages. However, the dynamics of fine particle deposition are still not completely understood in rivers, and continuum models like the advection dispersion equation require modifications to represent the processes accurately. To enhance understanding of fine particle dynamics, we developed a novel numerical particle tracking model that simulates fine particle deposition as a stochastic process under losing, neutral, and gaining streamflow conditions. These flow conditions generate three different velocity profiles by combining the free surface and groundwater flows. In addition, a novel aspect of our model is the storage of filtered particles to estimate concentration fields within the bed. Our simulated results are qualitatively compared with previous laboratory flume experimental results of kaolinite deposition under similar conditions. The model indicates that fine particle deposition patterns and residence time functions depend heavily on the exchange flux between stream and groundwater, as well as bed filtration properties as the deposition of particles occurs at greater depths in the losing stream condition than in the neutral and gaining cases. Therefore, the spatial pattern of particle deposition is a direct result of pore water velocity profiles, while the concentration depends on filtration dynamics within the bed.