On the Variability of Floc Characteristics in a Shallow Estuary
On the Variability of Floc Characteristics in a Shallow Estuary
复制标题
浅水河口絮体特性的变异性研究
DOI：
10.1029/2021jc018343
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Fringer, Oliver
中科院分区：
文献类型：
--
作者：
Egan, Galen;Chang, Grace;Manning, Andrew J.;Monismith, Stephen;Fringer, Oliver
我们在南旧金山湾进行了实地工作，以考察在浅水、波浪和海流驱动的河口环境中粘性沉积物的絮凝动力学。利用一套声学和光学仪器在三个不同季节收集的数据，我们发现，当比较本地来源的沉积物(即通过波浪驱动的再悬浮)和从上游平流来的悬浮沉积物时，驱动絮体尺寸变化的因素有很大不同。对我们广泛的现场数据的统计分析显示，这些趋势存在额外的季节性变化，在夏季和冬季，波浪应力促进了絮体的分解，而在春季生产期，生物过程促进了絮体的生长。结合这些数据和分维估计，我们发现，对于给定的絮体尺寸，随季节变化的絮体成分可以导致絮体沉降速度的差异约为两到五倍。最后，通过对底部边界层共同定位的湍流和泥沙通量测量结果的分析，我们证明了絮体大小与反湍流施密特数之间的关系随絮体结构的不同而不同。这些结果可以用来指导河口环境中泥沙输运的数值模拟。
We conducted field work in South San Francisco Bay to examine cohesive sediment flocculation dynamics in a shallow, wave‐ and current‐driven estuarine environment. Drawing on data collected using a suite of acoustic and optical instrumentation over three distinct seasons, we found that the factors driving floc size variability differed substantially when comparing locally sourced sediment (i.e., through wave‐driven resuspension) to suspended sediment advected from upstream. Statistical analysis of our extensive field data revealed additional seasonal variability in these trends, with wave stress promoting floc breakup during the summer and winter months, and biological processes encouraging floc growth during the spring productive period. Combining these data with fractal dimension estimates, we found that seasonally varying floc composition can lead to differences in floc settling velocity by a factor of approximately two to five for a given floc size. Finally, by analyzing co‐located turbulence and sediment flux measurements from the bottom boundary layer, we present evidence that the relationship between floc size and the inverse turbulent Schmidt number varies with floc structure. These results can be used to inform sediment transport modeling parameterizations in estuarine environments.