Unifying Advective and Diffusive Descriptions of Bedform Pumping in the Benthic Biolayer of Streams
Unifying Advective and Diffusive Descriptions of Bedform Pumping in the Benthic Biolayer of Streams
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DOI：
10.1029/2020wr027967
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发表时间：
2020-06
影响因子：
5.4
通讯作者：
S. Grant;A. Monofy;F. Boano;J. Gomez‐Velez;I. Guymer;J. Harvey;M. Ghisalberti
中科院分区：
文献类型：
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作者：
S. Grant;A. Monofy;F. Boano;J. Gomez‐Velez;I. Guymer;J. Harvey;M. Ghisalberti
河流发挥的许多水质和生态系统功能都发生在底栖生物层，即河床的生物活性上层（约5厘米）。底形泵送促进了通过底栖生物层的溶质输送，底形泵送是一种物理过程，在该过程中，静止底形表面上的动压和静压变化（例如，涟漪和沙丘）驱动水流穿过沉积物-水界面。在本文中，我们推导出两个预测模型框架，一个平流和其他扩散，通过底栖生物层的底形泵溶质运移。这两个框架密切再现模式和速率的底形泵先前在实验室中测量，扩散模型的扩散系数随深度呈指数下降。它们在功能上也是等效的，使得从2D平流模型推断的参数集可以应用于1D扩散模型，反之亦然。这两个模式的功能等效性和互补优势扩大了可以回答的问题的范围，例如，通过采用二维平流模式来研究地貌过程（如土地利用变化的底形调整）对流动依赖过程的影响，以及采用一维扩散模式来研究多种传输机制联合收割机的问题（如底形抽水和湍流扩散）。通过统一的二维平流和一维扩散描述的底形泵，我们的分析结果提供了一个简单的和计算效率高的方法来预测，更好地了解，在河流和沿海沉积物的底栖生物层的溶质运移。
Many water quality and ecosystem functions performed by streams occur in the benthic biolayer, the biologically active upper (~5 cm) layer of the streambed. Solute transport through the benthic biolayer is facilitated by bedform pumping, a physical process in which dynamic and static pressure variations over the surface of stationary bedforms (e.g., ripples and dunes) drive flow across the sediment‐water interface. In this paper we derive two predictive modeling frameworks, one advective and the other diffusive, for solute transport through the benthic biolayer by bedform pumping. Both frameworks closely reproduce patterns and rates of bedform pumping previously measured in the laboratory, provided that the diffusion model's dispersion coefficient declines exponentially with depth. They are also functionally equivalent, such that parameter sets inferred from the 2D advective model can be applied to the 1D diffusive model, and vice versa. The functional equivalence and complementary strengths of these two models expand the range of questions that can be answered, for example, by adopting the 2D advective model to study the effects of geomorphic processes (such as bedform adjustments to land use change) on flow‐dependent processes and the 1D diffusive model to study problems where multiple transport mechanisms combine (such as bedform pumping and turbulent diffusion). By unifying 2D advective and 1D diffusive descriptions of bedform pumping, our analytical results provide a straightforward and computationally efficient approach for predicting, and better understanding, solute transport in the benthic biolayer of streams and coastal sediments.