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General Session 1: Physical oceanic processes: Dynamics and physical-biological-biogeochemical interactions |
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On the variability of near-bed floc size due to complex interactions between turbulence, SSC, settling velocity, effective density and the fractal dimension of flocs
GS1-40-S
Yang Yang* , Key Laboratory for Coast and Island Development, Ministry of Education, Nanjing University, Nanjing 210023, China
Yaping Wang, Key Laboratory for Coast and Island Development, Ministry of Education, Nanjing University, Nanjing 210023, China
Chunyan Li, Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
Shu Gao, Key Laboratory for Coast and Island Development, Ministry of Education, Nanjing University, Nanjing 210023, China
Presenter Email: yangyang3811@126.com
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| Interactions between turbulence, suspended sediment concentration (SSC), settling velocity, effective density, fractal dimension, and floc size were studied on the tide-dominated, muddy coastal shelf of the southwestern Yellow Sea, China. The measurements were carried out in July 2013 at two sites located in water depths of 21.2 and 22.1 m, respectively. Negative correlations were observed between shear rate, SSC, effective density, and mean floc size, which supports the results of previous numerical, experimental, and field studies. A significant positive correlation was observed between near-bed SSC and shear rate, an indication that SSC variations are controlled by turbulence and re-suspension. In addition, significant linear relationships were found between settling velocity and other parameters (floc size, turbulence, SSC, effective density, and fractal dimension) at the two sites, indicating that the controlling factors on settling velocity are spatially variable. Principal component analysis was applied for to determine the relative importance of turbulence, flocculation ability, and SSC as controls on floc size in situ. The relative contributions of turbulence, flocculation ability, and SSC to floc size (at both sites) were ~33.0%, 30.3%, and 29.7%, respectively, this being a new field-based quantitative analysis of the controls on floc size. The findings demonstrate that, in nature, flocculation ability affects floc size to the same degree as turbulence and SSC. Therefore, predictions of floc size in coastal marine environments require constraints not only on turbulence and SSC, but also on flocculation ability. |
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