Scaling hyporheic exchange and its influence on biogeochemical reactions in aquatic ecosystems
Scaling hyporheic exchange and its influence on biogeochemical reactions in aquatic ecosystems
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DOI：
10.1029/2008wr007160
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发表时间：
2008-12
影响因子：
5.4
通讯作者：
B. O’Connor;J. Harvey
中科院分区：
文献类型：
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作者：
B. O’Connor;J. Harvey
由于溪流、湿地和近岸海洋生态系统固有的流体流动和沉积物条件的范围，因此难以量化潜流交换和生物地球化学反应。在水生系统中的非地球化学反应的现场测量受到阻碍，同时测量沉积物中的化学梯度的潜流的困难。已使用由沉积物-水界面处的流动和河床地形产生的达西定律开发了潜流交换的简化模型。然而，许多运输模式可能涉及（分子扩散，生物扰动，平流，剪切，床流动性和湍流），即使是简单的模型也难以应用于复杂的自然系统，其特征是沉积物大小可变和床的几何形状不规则。在这项研究中，我们综合了已发表的潜流交换调查的信息，以建立一个尺度关系，用于估计流体流动和沉积物条件下近地表沉积物中的传质。使用有效扩散系数（De）对净潜流交换进行量化，该系数集成了沉积物中同时发生的所有各种运输过程，并使用量纲分析将De缩放为描述流体流动和沉积物特性的剪切应力速度，粗糙度高度和渗透率。我们证明了衍生的缩放关系的价值，通过使用它来量化溶解氧（DO）的吸收速率的基础上，在沉积物中的溶解氧配置文件，并将它们与独立的通量测量。研究结果支持广泛应用的去标度关系量化耦合的潜流交换和生物地球化学反应速率的河流和其他水生生态系统，其特征在于复杂的流体流动和沉积条件。
Hyporheic exchange and biogeochemical reactions are difficult to quantify because of the range in fluid‐flow and sediment conditions inherent to streams, wetlands, and nearshore marine ecosystems. Field measurements of biogeochemical reactions in aquatic systems are impeded by the difficulty of measuring hyporheic flow simultaneously with chemical gradients in sediments. Simplified models of hyporheic exchange have been developed using Darcy's law generated by flow and bed topography at the sediment‐water interface. However, many modes of transport are potentially involved (molecular diffusion, bioturbation, advection, shear, bed mobility, and turbulence) with even simple models being difficult to apply in complex natural systems characterized by variable sediment sizes and irregular bed geometries. In this study, we synthesize information from published hyporheic exchange investigations to develop a scaling relationship for estimating mass transfer in near‐surface sediments across a range in fluid‐flow and sediment conditions. Net hyporheic exchange was quantified using an effective diffusion coefficient (De) that integrates all of the various transport processes that occur simultaneously in sediments, and dimensional analysis was used to scale De to shear stress velocity, roughness height, and permeability that describe fluid‐flow and sediment characteristics. We demonstrated the value of the derived scaling relationship by using it to quantify dissolved oxygen (DO) uptake rates on the basis of DO profiles in sediments and compared them to independent flux measurements. The results support a broad application of the De scaling relationship for quantifying coupled hyporheic exchange and biogeochemical reaction rates in streams and other aquatic ecosystems characterized by complex fluid‐flow and sediment conditions.