A laboratory assessment of the relative importance of turbulence, particle composition, and concentration in limiting maximal floc size and settling behaviour

Milligan, Timothy G.; Hill, Paul S.

doi:10.1016/s1385-1101(97)00062-2

Cited by 114 publications

(96 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…However, both models were derived from Smoluchowski's model (also called the rectilinear model) assuming that particles approach each other straightforwardly until collision occurs (O'Melia and Tiller, 1998). Therefore, the algal cell concentrations predicated by the models are much higher than those actually observed in the field (Millgan and Hill, 1998). Apparently, these models overestimated the collision efficiency by ignoring the influences of the hydrodynamic behavior and the structural morphology of aggregates on the interaction and flocculation between suspended particles in water.…”

Section: Introductionmentioning

confidence: 81%

Investigation of the hydrodynamic behavior of diatom aggregates using particle image velocimetry

Xiao

Lam

et al. 2012

Journal of Environmental Sciences

View full text Add to dashboard Cite

The hydrodynamic behavior of diatom aggregates has a significant influence on the interactions and flocculation kinetics of algae. However, characterization of the hydrodynamics of diatoms and diatom aggregates in water is rather difficult. In this laboratory study, an advanced visualization technique in particle image velocimetry (PIV) was employed to investigate the hydrodynamic properties of settling diatom aggregates. The experiments were conducted in a settling column filled with a suspension of fluorescent polymeric beads as seed tracers. A laser light sheet was generated by the PIV setup to illuminate a thin vertical planar region in the settling column, while the motions of particles were recorded by a high speed charge-coupled device (CCD) camera. This technique was able to capture the trajectories of the tracers when a diatom aggregate settled through the tracer suspension. The PIV results indicated directly the curvilinear feature of the streamlines around diatom aggregates. The rectilinear collision model largely overestimated the collision areas of the settling particles. Algae aggregates appeared to be highly porous and fractal, which allowed streamlines to penetrate into the aggregate interior. The diatom aggregates have a fluid collection efficiency of 10%-40%. The permeable feature of aggregates can significantly enhance the collisions and flocculation between the aggregates and other small particles including algal cells in water.

show abstract

Section: Introductionmentioning

confidence: 81%

Investigation of the hydrodynamic behavior of diatom aggregates using particle image velocimetry

Xiao

Lam

et al. 2012

Journal of Environmental Sciences

View full text Add to dashboard Cite

show abstract

“…Degradation can be due to physical disaggregation due to shear stress that tears aggregates apart (Milligan and Hill, 1998), but this process appears of limited importance at typical turbulent shear rates in the upper ocean . Turbulent shear rather puts an upper limit to the size of aggregates (Jackson et al, 1997).…”

Section: Mechanisms Of Aggregate Degradationmentioning

confidence: 99%

“…Aggregates may disintegrate physically Milligan and Hill, 1998), and they may be solubilized and remineralized by micro-organisms (Ploug et al, 1999;Smith et al, 1992) and zooplankton (Kiørboe, 2000). Likewise, faecal pellets may leak their contents of solute organics (Urban-Rich, 1999), and be consumed by zooplankters (Gonzales and Smetacek, 1994;Smetacek, 1980).…”

Section: Introductionmentioning

confidence: 99%

Formation and fate of marine snow: small-scale processes with large- scale implications

Kiørboe¹

2001

Sci. Mar.

213

176

View full text Add to dashboard Cite

SUMMARY: Marine snow aggregates are believed to be the main vehicles for vertical material transport in the ocean. However, aggregates are also sites of elevated heterotrophic activity, which may rather cause enhanced retention of aggregated material in the upper ocean. Small-scale biological-physical interactions govern the formation and fate of marine snow. Aggregates may form by physical coagulation: fluid motion causes collisions between small primary particles (e.g. phytoplankton) that may then stick together to form aggregates with enhanced sinking velocities. Bacteria may subsequently solubilise and remineralise aggregated particles. Because the solubilization rate exceeds the remineralization rate, organic solutes leak out of sinking aggregates. The leaking solutes spread by diffusion and advection and form a chemical trail in the wake of the sinking aggregate that may guide small zooplankters to the aggregate. Also, suspended bacteria may enjoy the elevated concentration of organic solutes in the plume. I explore these small-scale formation and degradation processes by means of models, experiments and field observations. The larger scale implications for the structure and functioning of pelagic food chains of export vs. retention of material will be discussed.

show abstract

“…density) of these grains within a floc can significantly affect their resultant size and settling velocity. It is this complexity that means it is not a simple task to mathematically describe the mud flocculation process on a fundamental basis (Milligan and Hill, 1998;Mikkelsen and Pejrup, 1998). The principle reason for such a poor understanding of cohesive sediment settling fluxes and deposition rates, has been principally due to a lack of reliable floc data, although the situation is now improving.…”

Section: Wwwintechopencommentioning

confidence: 99%

Cohesive Sediment Flocculation and the Application to Settling Flux Modelling

Manning¹,

Baugh²,

Spearman³

et al. 2011

Sediment Transport

View full text Add to dashboard Cite

A laboratory assessment of the relative importance of turbulence, particle composition, and concentration in limiting maximal floc size and settling behaviour

Cited by 114 publications

References 50 publications

Investigation of the hydrodynamic behavior of diatom aggregates using particle image velocimetry

Investigation of the hydrodynamic behavior of diatom aggregates using particle image velocimetry

Formation and fate of marine snow: small-scale processes with large- scale implications

Cohesive Sediment Flocculation and the Application to Settling Flux Modelling

Contact Info

Product

Resources

About