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The determination of the sizes and settling velocities of estuarine flocs by underwater video system
van Leussen, W.; Cornelisse, J.M. (1993). The determination of the sizes and settling velocities of estuarine flocs by underwater video system. Neth. J. Sea Res. 31(3): 231-241
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579, more
Peer reviewed article  

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Keyword
    Brackish water

Authors  Top 
  • van Leussen, W.
  • Cornelisse, J.M.

Abstract
    The in situ underwater video system VIS is described. VIS determines sizes and settling velocities of suspended mud flocs without destroying the large fragile aggregates. The settling process of the flocs and aggregates can be observed directly on a screen on board the research vessel. Analysis of the video recordings was possible up to 600 mg·dm-3, which is of importance in turbid estuarine systems. Experiments with VIS in the Ems estuary showed macroflocs with settling velocities of 0.5 to 2.0 mm·s-1 and sizes of 200 to 500 µm. These flocs were observed at relatively low suspended-sediment concentrations (20 to 50 mg·dm-3). During certain phases of the tidal cycle (around mid-tide) even larger aggregates were observed with dimensions in the range of 400 to 1100 µm and settling velocities of 1 to 7 mm·s-1, surviving relatively high current velocities. The large aggregates are shown to play an essential role in the phenomenon of rapid settling, as observed in various estuaries.

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