Sedimentation, particle size

Sediment nickel concentrations are grossly elevated near the nickel-copper smelter at Sudbury, Ontario, and downstream from steel manufacturing plants. Sediments from nickel-contaminated sites have between 20 and 5000 mg Ni/kg DW these values are at least 100 times lower at comparable uncontaminated sites (Chau and Kulikovsky-Cordeiro 1995). A decrease in the pH of water caused by acid rain may release some of the nickel in sediments to the water column (NRCC 1981). Transfer of nickel from water column to sediments is greatest when sediment particle size is comparatively small and sediments contain high concentrations of clays or organics (Bubb and Lester 1996). 

Xia X, Wang R (2008) Effect of sediment particle size on polycyclic aromatic hydrocarbon biodegradation importance of the sediment-water interface. Environ Toxicol Chem 27 119-125... 

Table 7.2 Commercial sedimentation particle size analyzers...

To ensure that only the finer fraction of the sediment slurry was processed, a shipboard centrifugal cone separator was connected to the slurry transfer hose to remove the coarse-sediment fraction. The cone separator was a 101.6-mm diameter, urethane-coated centrifugal cone (Demco 275). Under a normal operational pressure of 221 kPa the cone separator is capable of delivering 57.0 L/min of sediment slurry, whose sediment particle size ranged from 2 to 32 jitm as measured on the particle data Model 111 analyzer. 

An additional, and freqnently disregarded, problan is the role of particle size. Stratigraphic variation in sediment particle size will cause corresponding variations in elemental concentrations. It may be desirable to size fractionate sediment samples by sieving or settling prior to elemental analysis. 

See alsa Color Measurement. Environmental Analysis. Geochemistry Sediment. Particle Size Analysis. Sensors Photometric. Water Analysis Particle Characterization. 

Beach sediment Particle size (mm) Average slope of beach... 

Suspensk w jn 1 homogeneous suspension or off-bottom suspension sufficient restarting in settled sediment particle size solids concentration liquid and solids density... 

Figure 21.50 Comparison of TEM and ultracentrifugal sedimentation particle size analysis of C.l. PV55.

In the paper presented here I intend to describe some of the methods for sedimentation particle size analysis in current use. Although I do not intend to cover operating procedures it would be remiss of me not to mention the two factors which, more than anything else, lead to incorrect analyses. The first is incorrect sampling analyses are carried out on from a... 

The most important step in any sedimentation particle size analysis is the preparation of the suspension which must be carried out in such a way that a well dispersed suspension results. 5ml of this suspension is injected into the stationary disc and a reading taken of the maximum attenuation. The program will, on request, record this reading so that the 100% and 0% attenuation levels are now recorded. 

Parameters Appearing in Equation 10.4 as Function of Sediment Particle Size... 

Similar to EFDC, the SEDZLJ model simulates erosion of sediments into suspended load or bed load depending on the applied bed shear stress and the sediment particle size distribution at the surface of the bed. Fine-grained (i.e., cohesive) sediments are assumed to be transported entirely with the suspended load and therefore do not contribute to the bed load flux. For noncohesive sediments, the ratio of suspended load to total load transport (qs/qt) for eroding sediments is estimated using the following relationship, which is based on flume data collected by Guy etal.(1966) ... 

Oxides from the hydrothermal decomposition of thorium oxalate. Oxides prepared by the hydrothermal decomposition of the oxalate [27] at 300°C in a closed autoclave were found to be markedly different in their characteristic properties from the thermally prepared materials. The precipitation temperature of the oxalate had no effect on the final shape or size, and all evidence of the original oxalate structure had disappeared. Sedimentation particle-size analyses indicated particle sizes between 0.5 and 1 micron. 

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