From Substrate to Surface: A Turbulence‐Based Model for Gas Transfer Across Sediment‐Water‐Air Interfaces in Vegetated Streams
From Substrate to Surface: A Turbulence‐Based Model for Gas Transfer Across Sediment‐Water‐Air Interfaces in Vegetated Streams
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DOI：
10.1029/2021wr030776
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发表时间：
2021-12
影响因子：
5.4
通讯作者：
C. Tseng;R. Tinoco
中科院分区：
文献类型：
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作者：
C. Tseng;R. Tinoco
空气-水和沉积物-水界面（AWI 和 SWI）的溶解氧 (DO) 通量是控制水生生态系统中生物体可用氧量的两个主要过程。水生植被产生不同规模的湍流，改变 AWI 和 SWI 的流动结构并影响气体传输机制。在具有轻质沉积床的循环跑道水槽中进行了一系列用刚性圆柱阵列模拟植被的实验室实验。使用二维平面粒子图像测速来表征不同浸没比和阵列密度下的流场，以了解植被产生的湍流对气体传输的影响。通过 AWI 的气体传输速率由 DO 再通气曲线确定。穿过 SWI 的气体传输通量的有效扩散系数是通过近床层和近地表 DO 浓度之间的差异来估计的。当沉积物开始移动时，近床悬浮沉积物提供了负浮力项，根据植被流的修正表面更新模型，增加了表面气体传输过程的临界雷诺数。提出了一种使用近床湍流动能作为指标的新雷诺数依赖模型，为水生植被流中跨 SWI 的界面通量提供通用预测。这项研究为湖泊、河流和湿地等自然水环境的水质管理和生态系统恢复的未来研究提供了关键信息和有用的模型。
Dissolved Oxygen (DO) fluxes across the air‐water and sediment‐water interface (AWI and SWI) are two major processes that govern the amount of oxygen available to living organisms in aquatic ecosystems. Aquatic vegetation generates different scales of turbulence that change the flow structure and affect gas transfer mechanisms at AWI and SWI. A series of laboratory experiments with rigid cylinder arrays to mimic vegetation was conducted in a recirculating race‐track flume with a lightweight sediment bed. 2D Planar Particle Image Velocimetry was used to characterize the flow field under different submergence ratios and array densities to access the effect of vegetation‐generated turbulence on gas transfer. Gas transfer rate across AWI was determined by DO re‐aeration curves. The effective diffusion coefficient for gas transfer flux across SWI was estimated by the difference between near‐bed and near‐surface DO concentrations. When sediment begins to mobilize, near‐bed suspended sediment provides a negative buoyancy term that increases the critical Reynolds number for the surface gas transfer process according to a modified Surface Renewal model for vegetated flows. A new Reynolds number dependence model using near‐bed turbulent kinetic energy as an indicator is proposed to provide a universal prediction for the interfacial flux across SWI in flows with aquatic vegetation. This study provides critical information and useful models for future studies on water quality management and ecosystem restoration in natural water environments such as lakes, rivers, and wetlands.