inssev: An instrument to measure the size and settling velocity of flocs in situ

Fennessy, M. J.; Dyer, K.R.; Huntley, David A.

doi:10.1016/0025-3227(94)90009-4

Cited by 209 publications

(103 citation statements)

References 21 publications

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“…In situ settling velocities of fine-grained sediments are most commonly obtained using various settling column systems (Owen 1976;Dyer et al 1996), some of which are equipped with video cameras (Van Leussen and Cornelisse 1993;Fennessy et al 1994). Video-equipped settling columns usually provide floc size and settling velocity data, and several relationships between in situ floc size and settling velocity have been published Sternberg et al 1999;Mikkelsen and Pejrup 2001).…”

mentioning

confidence: 99%

“…Video-equipped settling columns usually provide floc size and settling velocity data, and several relationships between in situ floc size and settling velocity have been published Sternberg et al 1999;Mikkelsen and Pejrup 2001). Assuming Stokes Law, the densities of the flocs as a function of their size can subsequently be calculated and particle mass and/or settling fluxes can be derived for individual floc size classes (Syvitski et al 1995;Fennessy et al 1997;Hill et al 1998;Sternberg et al 1999;Manning and Dyer 2002).…”

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confidence: 99%

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INSSECT—an instrumented platform for investigating floc properties close to the seabed

Mikkelsen

Milligan

Hill

et al. 2004

Limnology & Ocean Methods

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A new type of tripod, INSSECT (IN situ Size and SEttling Column Tripod), designed for floc measurements in the shallow parts of the continental shelf, is described. INSSECT orientates itself into the current so that instrumentation on it faces upstream, thereby minimizing flow disturbance. The instrumentation includes a digital floc camera, a video settling column, a unique sediment trap designed for capturing flocs intact, a laser sizer, an optical backscatterance sensor, a compass and tilt meter, and a current meter. It is designed for relatively short deployments of up to 2 weeks and can be recovered, turned around, and redeployed rapidly. It was designed for use in semi-synoptic surveys of the spatial variation in floc properties such as size and settling velocity and the factors that influence them. The paper describes the various components of the INSSECT and presents selected results from the first deployments, demonstrating its ability to turn in the current and capture single flocs intact. Contrary to recent findings on the influence on settling columns on floc size, intercomparison between the video settling column and the digital floc camera reveals that the sizes are similar.

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confidence: 99%

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confidence: 99%

INSSECT—an instrumented platform for investigating floc properties close to the seabed

Mikkelsen

Milligan

Hill

et al. 2004

Limnology & Ocean Methods

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“…These microflocs can develop into large, but low dense flocs called macroflocs which behave very differently. Macroflocs have a diameter larger than 100 µm and a settling velocity between 1-15 mm/s (Fennessy et al 1994;Manning and Dyer 1999;Manning 2001;Manning et al 2013). …”

Section: Introductionmentioning

confidence: 99%

“…The flocculation process mainly occurs in the very low salinity region (between 1 and 2.5 ppt) (Wollast 1988), and it is affected by hydrodynamic changes which can alter the suspended sediment particle by modifying its effective particle size, shape, porosity, density and composition. Numerous studies have been carried out to investigate the flocculation phenomenon in the laboratory, such as (Serra et al 1997;Manning and Dyer 1999;Mikes et al 2004;Maggi 2005) and in situ (Fennessy et al 1994;Syvitski et al 1995;van Leussen and Cornelisse 1996). Due to the complexity of the natural system, many simplifications are made in laboratory studies in order to control the different variable parameters in the flocculation process.…”

Section: Introductionmentioning

confidence: 99%

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Effect of hydrodynamics factors on flocculation processes in estuaries

Mhashhash¹,

Bockelmann-Evans²,

Pan³

2016

Sustainable Hydraulics in the Era of Global Change

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Suspended Sediment Transport – Flocculation and Particle Characteristics

Droppo

2005

Encyclopedia of Hydrological Sciences

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In the history of sediment transport research within hydrological sciences, there has possibly been no greater paradigm shift than that which has been provided by the identification of flocculation as a dominant mechanism operating within, and mediating, cohesive suspended sediment transport. Flocculation (the process of aggregating smaller particles together to form larger particles) significantly modifies the hydrodynamic properties of the sediment by altering their effective size, shape, density, porosity, and composition. Such changes have a dramatic impact on the downward flux of sediments and as such influence the transportation and fate of suspended sediments. The traditional assumption of suspended sediment being inorganic individual grains for the quantification and modeling of sediment transport is likely to result in erroneous results and management decisions. Flocs settle faster than their individual constituent particles (but orders of magnitude slower than that predicted by Stokes' equation for a similar size), and, for large flocs, can have porosity close to 100% and a corresponding density close to that of water. Flocs are composed of significant living organic components (primarily bacteria) which produce an extracellular polymeric substance (fibrils) which glues particles together giving them greater strength than an electrochemically bound floc, and a pseudo plastic nature. Because of this active living component, flocs should be thought of as micro ecosystems (composed of a matrix of water, inorganic, and organic particles) with autonomous and interactive physical, chemical, and biological functions or behaviors operating within the floc matrix. A better understanding of how floc structure influences floc behavior will help to refine our knowledge and management of suspended sediment transport in a variety of aquatic ecosystems.

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inssev: An instrument to measure the size and settling velocity of flocs in situ

Cited by 209 publications

References 21 publications

INSSECT—an instrumented platform for investigating floc properties close to the seabed

INSSECT—an instrumented platform for investigating floc properties close to the seabed

Effect of hydrodynamics factors on flocculation processes in estuaries

Suspended Sediment Transport – Flocculation and Particle Characteristics

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