Virginia Institute of Marine Science
24th Biennial Conference of the Coastal and Estuarine Research Federation, Providence, RI
The goal of this study is to gain insight into the fractal properties of flocs in estuarine surface waters under conditions of variable floc size, density, concentration, and organic content. The properties of flocculated particles in estuarine surface waters are especially important to the fate of incident light, with direct ramifications for primary production, water quality, and optical remote sensing. Observations of particle properties were collected using a profiling system that includes a Laser In-Situ Scattering and Transmissometry (LISST) 100X Type C instrument, a high-definition Particle Imaging Camera System (PICS) incorporating a video settling tube, and a high-speed pump sampler. Results reported here were collected at a total of 45 sampling stations on nine cruises conducted in the York River Estuary, Virginia, between September and December over the course three years, 2014-2016. Samples were collected in the fall and early winter to avoid phytoplankton blooms, which are most likely to occur during spring and summer in this system. An aim of this study is to examine properties of flocculated particles without observations being significantly confounded by the presence of relatively large, intact algal cells. Preliminary results suggest that settling velocity and excess density as determined by the PICS in surface waters of the York River Estuary are very strongly fractal, with a median fractal dimension of ~2.3. However, particles with high organic content tend to have a significantly lower fractal dimension than particles with low organic content. For a given floc size, high organic content leads to lower floc density. But particle suspensions with higher inorganic content (and higher mass concentration overall) tend to have a larger median floc size, which leads to a lower bulk density for inorganic particles when integrated across all floc sizes.
flocculation, particle properties and suspended sediment
Fall, Kelsey; Friedrichs, Carl; Massey, Grace; and Bowers, David, "Fractal floc properties in estuarine surface waters: insights from video settling, LISST, and pump sampling" (2017). Presentations. 51.