Sedimentation incremental

Delumyea and McCleary report data for the determination of %w/w organic material in sediment samples collected at different depths from a cove on the St. Johns River in Jacksonville, FL. After collecting the sediment core it was sectioned into a set of 2-cm increments. Each increment was placed in 50 mb of deionized water and the slurry filtered through a piece of preweighed filter paper. The filter paper and sediment increment were then placed in a preweighed evaporating dish and dried in an oven at... 

Fault traps are of several varieties, but in all eases it is essential for the fault to be impervious and sealing. This is by no means always the case, and maity faults are open conduits to fluid movement. It is seldom possible to estab-hsh whether a fault is open or closed without drilling to test. Tension of the cmst generates normaF faults across which part of the sedimentary section is absent (Fig. 6B). The Fahud field of Oman is a good example of a normal fault petroleum trap. When a normal fault moves, the strata on the downthrown side often flop down into the space created by the fault movement. These are called rollover anticlines. It is often noted that strata thicken when traced from the upthrown to the downthrown side of the fault, and that the throw of the fault increases when measured downward from sediment increment to increment (Fig. 6C). 

In this technique, a sample is extracted from the sedimenting suspension at appropriate intervals by means of a pipette. These methods are incremental, and the sample is taken in one of two ways (a) at a fixed position in the app, or (b) at a fixed depth below the surface of the suspension. It is assumed in both instances that no disturbance of the suspension takes place by eddies, etc., while the sample is being taken, that the sample is representative of the suspension at the extraction point, and that the sample taken is small. Method (a) must take into account any lowering of the level of the top surface of the suspension... 

These instruments, sometimes referred to also as sediment accumulation devices, weight the sediment as it accumulates on a weigh-pan at the base of the sedimentation column. The methods are cumulative ones. With the development of sensitive electro balances, the cumulative sedimentation technique is generally easier to perform and more accurate than is the incremental technique. The powder may be dispersed initially in the bulk of the fluid or added instantaneously at the top. An advantage of this type of equipment is the absence of the conical base, needed in sediment extraction devices, upon the walls of which some sediment may adhere. The danger of particles sticking to the vertical walls is however still present... 

The various physical methods in use at present involve measurements, respectively, of osmotic pressure, light scattering, sedimentation equilibrium, sedimentation velocity in conjunction with diffusion, or solution viscosity. All except the last mentioned are absolute methods. Each requires extrapolation to infinite dilution for rigorous fulfillment of the requirements of theory. These various physical methods depend basically on evaluation of the thermodynamic properties of the solution (i.e., the change in free energy due to the presence of polymer molecules) or of the kinetic behavior (i.e., frictional coefficient or viscosity increment), or of a combination of the two. Polymer solutions usually exhibit deviations from their limiting infinite dilution behavior at remarkably low concentrations. Hence one is obliged not only to conduct the experiments at low concentrations but also to extrapolate to infinite dilution from measurements made at the lowest experimentally feasible concentrations. 

The 210Pb inventory in the sediments was calculated in a similar way to the 239,240pu method described previously, but 1 cm increments were used in determining the integrated deposition. The deposition rate of the 210Pb for each core was determined as the product of the integrated deposition and the radioactive decay constant, (A. =. 0311 yr-1). Since the unsupported 210Pb (t ... 

When other sediments known to support PCB dechlorination were inoculated with PCB-dechlorinating microorganisms and amended with incremental increases of pure petroleum hydrocarbons (0-4 wt%) or 6.2 % petroleum hydrocarbons extracted from Silver Lake sediments, a reduction in both the rate and extent of PCB dechlorination occurred. 

Itou et al. [60] determined 0II/0C for isotropic solutions of poly(n-hexyl isocyanate) (PHIC) and dichloromethane (DCM) from sedimentation equilibrium data on narrow distribution PHIC samples. Figure 3 shows their results, where the ordinate Mw(0II/0c) represents the osmotic pressure increment on the molar concentration scale. 

Imagine that system B is the water column of a lake and system A is the pore space of the lake sediments. In B, mixing is by turbulence and fairly intensive while in system A transport is by molecular diffusion. The above case corresponds to a situation in which at time t the concentration of a compound in the water suddenly rises to the value Cg. Then Eqs. 19-25 and 19-26 describe the cumulative and incremental mass flux of the compound into the infinitely deep sediment column. 

The analysis of mixed associations by light scattering and sedimentation equilibrium experiments has been restricted so far to ideal, dilute solutions. Also it has been necessary to assume that the refractive index increments as well as the partial specific volumes of the associating species are equal. These two restrictions are removed in this study. Using some simple assumptions, methods are reported for the analysis of ideal or nonideal mixed associations by either experimental technique. The advantages and disadvantages of these two techniques for studying mixed associations are discussed. The application of these methods to various types of mixed associations is presented. 

The sedimentation equilibrium experiment requires much smaller volumes of solution, about 0.15 ml. With six-hole rotors and multichannel centerpieces (41) it is potentially possible to do fifteen experiments at the same time. For situations where the photoelectric scanner can be used one might (depending on the extinct coefficients) be able to go to much lower concentrations. Dust is no problem since the centrifugal field causes it to go to the cell bottom. For conventional sedimentation equilibrium experiments, the analysis of mixed associations under nonideal conditions may be virtually impossible. Also, sedimentation equilibrium experiments take time, although methods are available to reduce this somewhat (42, 43). For certain situations the combination of optical systems available to the ultracentrifuge may allow for the most precise analysis of a mixed association. The Archibald experiment may suffer some loss in precision since one must extrapolate the data to the cell extremes (rm and r6) to obtain MW(M, which must then be extrapolated to zero time. Nevertheless, all three methods indicate that it is quite possible to study mixed associations. We have indicated some approaches that could be used to overcome problems of nonideality, unequal refractive index increments, and unequal partial specific volumes. 

In this paper we have used the quantity (1 — vp0) in writing equations for sedimentation equilibrium experiments. Some workers prefer to use the density increment, 1000(dp/dc)Tfn, instead when dealing with solutions containing ionizing macromolecules. This procedure was first advocated by Vrij (44), and its advantages are discussed by Casassa and Eisenberg (39). Nichol and Ogston (13) have used the density increment in their analysis of mixed associations. The subscript p. means that all of the diffusible solutes are at constant chemical potential in the buffer... 

TIF TU TUdw U.S. ACE U.S. EPA WAPT WS WT Toxicity Incremental Factor Toxic Unit Toxic Unit expressed on a dry weight basis United States Army Corps of Engineers United States Environmental Protection Agency Weighed Average of Phase Toxicity Whole Sediment Wet Sediment. 

It is easier experimentally to determine 5 than to perform an equilibrium sedimentation measurement, but, because we are interested in the molar mass and the density increment, D has to be determined independently. 

Anywhere a chemical potential increment or gradient exists, an elementary separation step can occur. Anywhere random flow currents exist, separation is dissipated. Thus random flow currents are parasitic in regions where incremental chemical potential is used for separation. These currents should thus be eliminated, insofar as possible, in regions where electrical, sedimentation, and other continuous (c) fields are generating separations. Likewise, they should not be allowed to transport matter over discontinuous (d) separative interfaces such as phase boundaries or membrane surfaces. However, they are nonparasitic in bulk phases (removed from the separative interface) where only diffusion occurs. Here, in fact, they aid diffusion and speed the approach to equilibrium. This positive role is recognized in the following category of flow. 

The mean annual increment of the new delta amounted to 0.27 km2 year-1 for 20 years (from 1939 to 1958). In 1959-1967, the rate of the delta growth slowed down to 0.1 km2 year-1 because of the decrease in sediment load after the construction of the Gumati Hydroelectric Plant, the partial diver-... 

A study was conducted of six Louisiana lakes to examine the relationship between sediment properties including Hg content and health advisories associated with Hg in fish [31]. Comparison was made between three lakes with health advisories (Black Lake, Chicot Lake, and Henderson Lake) and three lakes where the levels of Hg in fish are below health advisory levels (False River, Lake St John, and Miller Lake). Three sediment core samples were collected from each lake and sectioned into 2 cm increments to a depth of 20 cm. Sediment properties measured in each depth increment of the sediment profile included total Hg, 137Cs activity (for sedimentation rate), and sediment organic matter content. Of the lakes studied, those lakes that have health advisories for Hg tended to have higher total Hg contents, usually higher sediment organic matter contents, and higher sedimentation rates than sediments in lakes where health advisories for Hg are not issued. 

Rezanowich A, Yean WQ, Goring DAI (1963) The molecular properties of milled wood and dioxane lignins sedimentation, diffusion, viscosity, refractive index increment and ultraviolet absorption Sven Papperstidn 66 141-149 Sarkanen KV, Chang H-M, Allan GG (1967) Species variations in lignin (2) Conifer lignins (3) Hardwood lignins Tappi 50 583-590... 

BS 3406, British Standard Method for determinig Particle Size Distribution is a comprehensive standard that includes methods for both incremental and cumulative methods of particle size deterination. Part 1, 1984, covers Recommendations for Gravitational Liquid Sedimentation Mehods for Powders and Suspensions. Part 5, 1985 covers... 

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