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CONSTANCY OF THE RELATION BETWEEN FLOC SIZE AND DENSITY IN SAN FRANCISCO BAY
Citation:
Gangu, N., M. Schoellhamer, M C. Murrell, Gartner, AND S. Wright. CONSTANCY OF THE RELATION BETWEEN FLOC SIZE AND DENSITY IN SAN FRANCISCO BAY. 7th INTERCOH, Gloucester Point, VA, October 01 - 04, 2003. Elsevier (ed.), BULLETIN OF MARINE SCIENCE. Elsevier Science Ltd, New York, NY, 8:75-92, (2006).
Impact/Purpose:
non-EPA published proceedings
Description:
Ganju, N.K., D.H. Schoellhamer, M.C. Murrell, J.W. Gartner and S.A. Wright. In press. Constancy of the Relation Between Floc Size and Density in San Francisco Bay. In: INTERCOH 2003: Proceedings of the 7th International Conference on Nearshore and Estuarine Cohesive Sediment Transport Processes. Elsevier, New York, NY. 15 p. (ERL,GB 1209).
The size and density of fine sediment aggregates, or flocs, governs their erosional, transport, and depositional properties. While the mass and volume concentrations of flocs can be measured directly or by optical methods, both must be simultaneously determined to gain an accurate density measurement. Results are presented from a tidal cycle study in San Francisco Bay, where mass concentration was determined directly, and volume concentration was measured in 32 size bins by laser-diffraction methods. A relationship between floc size and density is developed assuming a constant primary particle size and fractal floc dimension. This relation is validated with measurements from several sites throughout San Francisco Bay. The constancy of this relation implies a uniform primary particle size throughout the Bay, as well as uniform aggregation/disaggregation mechanisms (which modify fractal dimension). The exception to the relation is identified during near-bed measurements, when advected flocs mix with recently resuspended flocs from the bed, which typically have a higher fractal dimension than suspended flocs. The constant relation for suspended flocs simplifies monitoring and numerical modeling of suspended sediment.
Conference held 1-4 October 2003, Virginia Institute of Marine Science, College of William & Mary, Gloucester Point, VA.