Dynamics of Hyporheic Exchange Flux and Fine Particle Deposition Under Moving Bedforms
Dynamics of Hyporheic Exchange Flux and Fine Particle Deposition Under Moving Bedforms
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DOI：
10.1029/2020wr028541
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发表时间：
2021-04
影响因子：
5.4
通讯作者：
Y. Teitelbaum;J. Dallmann;C. Phillips;A. Packman;R. Schumer;N. Sund;S. Hansen;S. Arnon
中科院分区：
文献类型：
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作者：
Y. Teitelbaum;J. Dallmann;C. Phillips;A. Packman;R. Schumer;N. Sund;S. Hansen;S. Arnon
细悬浮颗粒的沉积会降低低通量交换通量（HEF），从而导致各种生态过程的破坏。然而，细颗粒沉积和河床堵塞的动力学仍然没有得到很好的理解，特别是当河床处于运动状态时。我们通过水槽实验，研究了悬浮高岭石间歇（脉冲）输入时砂-粘土耦合动力学对HEF的影响。在流动沙床和恒定放电条件下，分别以固定浓度增量0.16、0.41和0.66 g/L反复注入悬浮高岭石脉冲。利用示踪剂测试评估HEF和参与孔隙水体积。高岭石沉积速率由浊度测量推断，沉积模式由岩心样品测量。我们发现，细粒沉积物主要聚集在河床冲刷带下方的一层内，当高岭石以更大的脉冲加入时，这一层变得更厚。随着高岭石在河床沉积物中积累，HEF随时间呈线性下降；无论脉冲浓度如何，床层中高岭石含量增加0.1%导致HEF下降26.6 cm/d。然而，同样的高岭石增加导致较大高岭石脉冲的参与孔体积减少50%，而最小脉冲仅减少30%。这些结果表明，堵塞不仅发生在高流量事件期间和之后，也发生在恒定流量条件下，即HEF对悬浮粘土的幕式沉积导致床层中形成低导电性层。
Deposition of fine suspended particles can reduce hyporheic exchange flux (HEF), which may result in impairment of various ecological processes. However, the dynamics of fine particle deposition and streambed clogging are still not well understood, especially when the bed is in motion. We conducted flume experiments to study the effects of coupled sand‐clay dynamics on HEF with episodic (pulse) inputs of suspended kaolinite. Three experiments with a mobile sand bed and constant discharge were conducted with repeated injection of suspended kaolinite pulses at fixed concentration increments of 0.16, 0.41, and 0.66 g/L, respectively. HEF and participating porewater volume were assessed using tracer tests. Kaolinite deposition rates were inferred from turbidity measurements while deposition patterns were measured using core samples. We found that fine sediment primarily accumulated within a layer below the bedform scour zone, and that this layer was thicker when kaolinite was added in larger pulses. HEF declined linearly over time as kaolinite accumulated in the bed sediment; an increase of 0.1% kaolinite in the bed led to a decrease in HEF of 26.6 cm/day, regardless of the pulse concentration. However, the same kaolinite increase led to a reduction of 50% in participating pore volume for larger kaolinite pulses, versus only 30% for the smallest pulse. These results indicate that clogging occurs not just during and after high‐flow events, but also under constant flow conditions in which episodic deposition of suspended clay by HEF leads to the formation of a low‐conductivity layer in the bed.