Settling and coagulation characteristics of fluorescent particles determined by flow cytometry and fluorometry

Newman, Kathleen A.; Morel, François M. M.; Stolzenbach, Keith D.

doi:10.1021/es00074a007

Cited by 13 publications

(11 citation statements)

References 9 publications

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“…This is expected because the pigment particles used in these experiments are known to be very stable with respect to self-coagulation. Although a range of particle sizes can cause apparent second-order loss from the water column [Newman et aL, 1990a], deviations from first order are not evident in these data since the pigment particles were presettl ed to narrow the size distribution and remove the large, fast-settlin g particles(> 0.1 m day-1 ) and because pure settling produces less than 20% loss from the water column over the course of the experiment. The difference in removal rate between column D and the columns with a fluidized interfacial layer (A and E) must be attributed to an interfacial process, as the water column conditions were similar.…”

Section: Resultsmentioning

confidence: 80%

“…Scuba divers collecting cores in Salem Sound observed a mobile interfacial layer of the order of 1 cm deep being sheared by long-wave swells. Considering the relatively low collision efficiency of the tracer particles (o: = 5 X 104) [Newman et al, 1990a], we conclude that effective deposition velocities for natural fine particles with higher collision efficiencies (O! = 10-2 to 10-1) could be at least an order of magnitude higher, i.e., 1 to 10 m day-1 at this site.…”

Section: Resultsmentioning

confidence: 88%

“…Flow cytometric analysis of sediment cores indicated that a minimum of7% of the tracer mass reached the sediment in the sound within 8 days after being introduced through a sewage outfall . However, the field samples contained significantly more of the smallest tracer particles (down to about 0.5 µm in radius) than could be · explained the basis of settling rates measured in the laboratory [Newman et al, 1990a]. In fact, measured size distributions of tracer particles in bottom sediments were essentially identical to that of the initial stock of pigment particles.…”

Section: Resultsmentioning

confidence: 90%

“…Assuming that the solids content of the active layer was about q, = 0.1 (typical of reported averages in the upper top centimeter), deposition of fine particles with O! = 5 X 104 [Newman et al, 1990a] at a rate V1 = 0.26 m day-1 requires a shear rate G = 20 s-1 . This magnitude of interfacial shear, equivalent to linear variation in velocity from zero to 20 cm s-1 over a distance of 1 cm, is consistent with the observations of the layer movement by waves.…”

Section: Theorymentioning

confidence: 99%

“…According to our hypothesis, fine particles are continually [Newman et al, 1990a]. A stock suspension ( -5000 ppm) of small (1 µm), slow-settlin g (0.017 m day-1 ) pigment particles was isolated by decanting a suspension of the original pigment after sett ling for one day through an 8-cm water column.…”

Section: Introductionmentioning

confidence: 99%

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Aggregation of fine particles at the sediment‐water interface

Stolzenbach¹,

Newman²,

Wong³

1992

J. Geophys. Res.

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The presence of a bottom sediment layer agitated by mechanical stirring or by resident organisma (tubificid oligochaetes) significantly increases the rate at which fine (1 ,um) cohesive particles are removed from suspension in laboratory columns. Measured rates of particle removal are equivalent to deposition velocities ranging from 0.23 m day-1 to 0.41 m day1. These rates are an order of magnitude faster than deposition by gravitational settling or coagulation with larger particles in the water column as observed in experimental controls. It is hypothesized that the increased removal rate is the result of aggregation in a sediment layer at the bed-water interface characterized by loosely bound (fluffy), porous material hydrodynamically coupled to the water column. According to this hypothesis particle removal occurs when motion of the overlying water or organism activity causes suspended fine particles to collide with and stick to the interfacial sediment. This new hypothesis is supported by the mass and size distribution of tracer particles recovered in cores and sediment traps at a coastal site and by theoretical estimates of interfacial aggregation rates. INTRODUCTIONA significant fraction of the total mass of suspended material in natural water bodies is composed of particles smaller than 10 µm [Lal and Lerman, 1975;McCave, 1975;Clegg and Whitfield, 1990]. The transport of these fine particles is important in the geochemical cycling of natural elements and the fate of anthropogenic contaminants. Of particular significance is the rate at which fine particles are deposited in bottom sediments. McCave [1985a, b] concludes that particle settling exceeds other possible deposition modes such as Brownian diffusion through a benthic boundary layer. However, particles smaller than 10 µm settle so slowly (less than 1 m day-1 for marine sediments [McCave, 1984], cells [Smayda, 1970], and sewage [Hunt and Pandya, 1984;Wang, 1988]) that in the absence of other deposition mechanisms, they would remain in the water column for weeks to years in lakes and coastal waters and for decades in the deep ocean. For this reason, the dominant process for the deposition of fi ne particles has been thought to be their incorporation into larger, faster-settling aggregates by coagulation or biogenic repackaging in the water column [Edzwald et al., 1979;McCave, 1984;Hunt and Pandya, 1984;Farley and Morel, 1986;Fowler and Knauer, 1986].In this article we present laboratory experiments in support of a new hypothesis that fine particles are removed from suspension by aggregation in a hydrodynamically active "fluff" layer at the sediment-water interface. Measured rates of removal by this mechanism are significantly faster than rates of removal by settling of primary particles or by coagulation with larger particles in the water column. We conclude that interfacial aggregation may regulate the deposition of fi ne particles, particularly in the sub-micron size range. Copyright 1992 by the American Geophysical Union.Paper number 92JC01827. 014...

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Section: Resultsmentioning

confidence: 80%

Section: Resultsmentioning

confidence: 88%

Section: Resultsmentioning

confidence: 90%

Section: Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Aggregation of fine particles at the sediment‐water interface

Stolzenbach¹,

Newman²,

Wong³

1992

J. Geophys. Res.

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Rapid settling of nanoparticles due to heteroaggregation with suspended sediment

Velzeboer

Quik

Meent

et al. 2014

Enviro Toxic and Chemistry

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Sedimentation of engineered nanoparticles (ENPs) has been studied mainly in artificial media and stagnant systems mimicking natural waters. This neglects the role of turbulence and heteroaggregation with sediment. The authors studied the apparent sedimentation rates of selected ENPs (cerium dioxide [CeO2 ], polyvinylpyrrolidone-capped silver [PVP-Ag], and silica-coated silver [SiO2 -Ag]) in agitated sediment-water systems resembling fresh, estuarine, and marine waters. Experiments were designed to mimic low energy and periodically resuspended sediment water systems (14 d), followed by a long-term aging, resuspension, and settling phase (6 months), as would occur in receiving shallow lakes. The ENPs in systems with periodical resuspension of sediment were removed with sedimentation rates between 0.14 m/d and 0.50 m/d. The sedimentation rates did not vary much among ENP type, salinity, and aging time, which is attributed to the capture of ENPs in sediment flocks. The sedimentation rates were 1 to 2 orders of magnitude higher than those reported for aggregation-sedimentation in stagnant systems without suspended sediment. Heteroaggregation rates were estimated and ranged between 0.151 L/mg/d and 0.547 L/mg/d, which is up to 29 times higher than those reported for natural colloids under quiescent settling conditions. The authors conclude that rapid scavenging and sedimentation drives removal of ENPs from the water column.

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Fluorescence Spectroscopy in Environmental and Hydrological Sciences

Goldberg

Weiner

1993

Fluorescence Spectroscopy

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Settling and coagulation characteristics of fluorescent particles determined by flow cytometry and fluorometry

Cited by 13 publications

References 9 publications

Aggregation of fine particles at the sediment‐water interface

Aggregation of fine particles at the sediment‐water interface

Rapid settling of nanoparticles due to heteroaggregation with suspended sediment

Fluorescence Spectroscopy in Environmental and Hydrological Sciences

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