Sedimentation profiles

Piazza R, Bellini T and Degiorgio V 1993 Equilibrium sedimentation profiles of screened charged colloids a test of the hard-sphere equation of state Rhys. Rev. Lett. 71 4267-70... 

Now, we need a boundary condition to determine /3i. This is difficult with suspended sediment profiles. We can develop a fairly good estimate of the distribution of suspended sediment once we have a known concentration at some location in the flow field. In the sediment transport field, bed load and suspended load are often discussed. The relation between the two, and some experience and measurements of both simultaneously, can be used to predict an equivalent suspended sediment concentration at the bed. Then, the relevant boundary condition of equation (E5.2.11) is... 

Figure 7. Sediment profiles of base cations in treatment basin (shaded bar) and reference basin (unshaded bar), 5-m sites, October 1987. Key a, total b, organic fraction and c, exchangeable fraction. All are expressed in milli-equivalents per 100 g of wet sediment.

An understanding of the retention of sulfur in lake sediments is important for paleolimnological reconstructions, for an understanding of the alkalinity balance of lakes, for determination of rates and pathways of diagenesis, and for an understanding of the dynamics of the microbial loop in sediments. Profiles of rates and forms of S accumulation in sediments may preserve records of past conditions of climate, lake chemistry, or atmospheric de-... 

Paleolimnological Conditions. Because of the interplay between primary production, oxygen content of bottom waters, and the sulfur content and speciation of sediments, sediment profiles of S probably preserve records of paleolimnological conditions. Several studies (23-25, 205) point to increased S content of sediments as a result of eutrophication. Mechanisms involve both rates of S supply to sediments (seston deposition and diffusive gradients) and rates of S reduction and oxidation. The relative S enrichment... 

Net sedimentation is defined as the flux of material incorporated into the permanent sediment record. 210Pb and 137Cs geochronologies indicate a mass sedimentation rate of 103 g/m2 per year for profundal sediments in Little Rock Lake. By using the mean Hg concentration (118 ng/g) in the top 1-cm slice of our bulk sediment profile, we estimated an annual net sedimentation of 12 xg of HgT/m2 per year. This net accumulation rate is similar to the calculated atmospheric input rate of about 10 xg/m2 per year (18, 19). Additionally, gross deposition rates (from sediment traps) exceeded these estimates by about a factor of 3 this rate suggests substantial internal recycling of material deposited at the sediment-water interface in this lake. 

Horneman, A., van Geen, A., Kent, D.V. et al. (2004) Decoupling of As and Fe release to Bangladesh groundwater under reducing conditions. Part I evidence from sediment profiles. Geochimica et Cosmochimica Acta, 68(17), 3459-73. 

An application of ultrasound that is becoming increasingly popular in the food industry is the determination of creaming and sedimentation profiles in emulsions and suspensions (Basaran et al., 1998). Acoustic techniques can also assess nondestructively the texture of aerated food products such as crackers and wafers. Air cells, which are critical to consumer appreciation of baked product quality, are readily probed due to their inherent compressibility (Elmehdi et al., 2003). Kulmyrzaev et al. (2000) developed an ultrasonic reflectance spectrometer to relate ultrasonic reflectance spectra to bubble characteristics of aerated foods. Experiments were carried out using foams with different bubble concentration and the results showed that ultrasonic reflectance spectrometry is sensitive to changes in bubble size and concentration of aerated foods. 

Sediment. Highly stratified sediments from Green Lake in upstate New York had CDD concentrations that could be correlated with atmospheric deposition. CDDs could be detected as far back as 1860-1865 at a total CDD concentration of 7 ppt 98% of all CDDs detected were OCDD. The CDD sediment profile showed a strong increase after 1923 and continued to increase until 1984 (the last year analyzed), with a maximum concentration of >900 ppt, of which 75% was OCDD (Smith et al. 1992). 

Figure 13.7 Vertical sediment profiles of SO42 and CH4 in the anoxic fjord, Sannich Inlet. (Modified from Murray et al., 1978, and Devol et al., 1984.)...

Figure 13.16 Down-core sediment profiles of (a) total organic carbon (TOC) and (b) atomic C N ratios at two locations in the York River estuary. (Modified from Arzayus...

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