Sediment transport investigation in a karst aquifer hypothesizes controls on internal versus external sediment origin and saturation impact on hysteresis
Sediment transport investigation in a karst aquifer hypothesizes controls on internal versus external sediment origin and saturation impact on hysteresis
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岩溶含水层中的沉积物输运研究假设控制内部与外部沉积物来源以及饱和度对滞后的影响
DOI：
10.1016/j.jhydrol.2022.128391
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发表时间：
2022
影响因子：
6.4
通讯作者：
Gold-McCoy, Ariel
中科院分区：
文献类型：
--
作者：
Bettel, Leonie;Fox, Jimmy;Husic, Admin;Zhu, Junfeng;Al Aamery, Nabil;Mahoney, Tyler;Gold-McCoy, Ariel
岩溶泉是全球人口的主要饮用水源，但仍不确定沉积物等污染物如何通过岩溶。我们发现有关控制沉积物输送的时间和幅度的过程的知识差距。为了填补这些知识空白，我们：（1）收集了美国肯塔基州内蓝草地区三条地表河流和两个洞穴的高频沉积物和电导率数据;（2）分析了两年期间51次风暴事件的沉积物滞后;（3）数值模拟了含水层中的沉积物输运;（4）将我们的结果与欧洲和北美十个岩溶泉的荟萃分析相结合。我们的研究结果表明，80%的风暴事件来自外部输入通过下沉流的沉积物，而其余的20%的特点是以前沉积的洞穴沉积物的内部再悬浮。我们发现，内部泥沙输运成正比的流体剪切应力在洞穴中，完全饱和的含水层条件下发生的风暴事件之前。在部分饱和的含水层条件下，外部来源的沉积物脉冲有效地路由到弹簧，而不管剪切的管道网络。沉积物滞后在表面流是顺时针方向，而洞穴网站经历了逆时针方向的行为。顺时针和逆时针滞后通常是指近端和远端的来源流，但我们的研究结果表明，这种解释是无效的地下岩溶环境。岩溶滞后模式显示依赖于含水层和内部与外部来源的前期水条件。荟萃分析结果表明，尽管变异性很大，逆时针模式的沉积物滞后是非常常见的岩溶，这与沉积物滞后在地面流。结果表明，外部泥沙负荷，而不是内部再悬浮是最常见的控制泥沙负荷在泉，这应通知岩溶地下水资源管理。
Karst springs serve as major drinking water sources for the global population, yet there remains uncertainty regarding how contaminants like sediment are routed through karst. We find knowledge gaps pertaining to the processes that control the timing and magnitude of sediment delivery. To close these knowledge gaps, we: (1) collected high-frequency sediment and conductivity data from three surface streams and two cave sites in the inner bluegrass region of Kentucky, USA; (2) analyzed sediment hysteresis for 51 storm events over a two year period; (3) numerically modeled sediment transport through the aquifer; and (4) contextualized our results with a meta-analysis of ten karst springs in Europe and North America. Our results showed that 80% of storm events derived their sediment from external inputs through sinking streams while the remaining 20% were characterized by only internal resuspension of previously deposited cave sediment. We found that internal sediment transport was proportional to fluid shear stress in the cave and occurred exclusively during fully saturated aquifer conditions prior to the storm event. During partially-saturated aquifer conditions, externally sourced sediment pulses were efficiently routed to the spring irrespective of shear in the conduit network. Sediment hysteresis in surface streams was clockwise whereas the cave sites experienced counter-clockwise behavior. Clockwise and counter-clockwise hysteresis typically refer to proximal and distal sourcing for streams, but our findings suggest that this interpretation is not valid for subsurface karst settings. Hysteresis patterns for karst show dependence on the antecedent water conditions in the aquifer and internal versus external sourcing. meta-analysis results show that, despite high variability, counter-clockwise patterns of sediment hysteresis are very common for karst, which contrasts sediment hysteresis in surface streams. Results suggest that external sediment loading rather than internal resuspension is the most common control of sediment load at springs, which should inform management of karst groundwater resources.
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