Retention ratio, sedimentation

The following equations are involved in sedimentation FFF. The retention ratio, R ... 

Finally, it must be said that in most of the practical cases, retention ratio and peak width are satisfactorily predicted by the 2D models. The role of the 3D models was to estimate the contributions of the 3D effects and to determine the optimal conditions when these contributions are neghgible. As it was shown, to minimize the 3D effects, one must use FFF channels with a larger breadth-to-width ratio, use the syringe inlet, and/or use the longer endpieces with the sharper angle in the case of sedimentation FFF, one is to avoid codirected flow and rotation mode. 

Figure 7.3.21. Field-flow fractionation (FFF). (a) Basic configuration of field-flow fractionation device and the detector response to a sample, (b) Retention ratio of species i vs. retention parameter X. (c) Schematic for flow field-flow fractionation with a cros ow. (d) Fhysical configuration/dimensions of a FFF channel with inlet/outlet. (e) Configuration of the channel in sedimentation FFF. (After Giddings (1993).)...

Primary production (trophic state) affects S retention and speciation in several ways. As primary production increases, inputs of organic S to sediments in seston increase. Hence, as the organic carbon content of sediments increases, S content would be expected to increase proportionally. Such a simple relationship is not observed among nearly 80 lakes for which sediment S and C content are available (Figure IB). However, a line defining the minimum S content does increase linearly with increasing carbon content. The slope of this line corresponds to the mean C S ratio measured in seston... 

If iron limits retention of S in sediments (cf. 50, 30) it would be expected that the fraction of S present as iron sulfides would increase with increasing Fe content of sediments. Although this relationship is observed in deep sediments (Figure 7), fractionation of S between organic and inorganic forms is not determined by iron content in surface sediments. Nor is there any relationship between Fe content and total S content in surface sediments for all lakes reported in the literature (Figure lc). In deep sediments where C S ratios indicate that seston was the major source of sedimentary sulfur... 

Figure 9. A, At the base of sediment cores (30-50 cm) from 48 lakes ratios of C SMat nearly equal the ratio found in seston (indicated by the line labeled mean algal C S). A simplistic explanation is that most of the S is derived from seston, and that C and S are mineralized and lost from sediments at similar rates. B, Within the same cores for which data were available, ratios of C S oni tend to be lower than the ratio in seston (19 of 28 points lie below the line). Together, the figures suggest that much of the mineralized S is retained within the sediments. Figure 7 suggests that such retention is dependent on the avail-ability of iron. References are given in Figure 1.

In little Rock Lake, seston deposition appears to be a more important sulfate sink than does dissimilatory reduction. Several previous studies (2.41 have concluded that dissimilatoiy reduction is the major mechanism for sulfate retention, and Cook et al. (2) concluded that seston deposition was a minor sulfate sink in experimentally acidified Lake 223. The C/S ratio calculations discussed above snow that approximately 29% of the total S in recent sediments at SB-5 is excess-S derived from dissimilatory reduction and the remaining 71% originated from seston deposition. 

The sedimentation coefficient s> often used to characterize biological macromolecules and particles, is equal to the ratio of the velocity U induced by a sedimentation field to the strength G of that field measured as acceleration. Show that s can be related to the retention parameter A in sedimentation FFF by s = D Gw. 

Anthropogenic activities involved in the production, distribution, consumption, and disposal of lead and lead products produce estimates of lead emissions that are many times the amount assigned to natural emission rates. The rates in prior years would have been higher and the ratios of anthropogenic to natural emissions are much higher, but the retention of those past emissions in soil and sediment environmental compartments means that the amounts of anthropogenic lead in the human and ecological environments... 

Volatilization defines the partitioning of a chemical between water and air. Adsorption defines the partitioning of a chemical between water and soil. In the process of adsorption, which is also referred to variously as sorption or retention, molecules move back and forth between being dissolved in water and being attached to the surfaces of soil or sediment particles with which the water is in contact. How a chemical distributes itself between being adsorbed to soil and dissolved in water is described by the adsorption coefficient, or the soihwater partition coefficient. The ratio of the concentrations of adsorbed to dissolved chemical at equilibrium under standard conditions is ... 

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