Bulk sediment properties

Bulk sediment properties and particle sizes affect the resistance to shear, which depends on velocity and bed roughness. Chemical properties that influence the likelihood of scour include those that determine interparticle attraction, so the list is similar to those that affect deposition. These include... 

All solid phase tests measure toxicity relative to a negative control or reference sediment (ASTM, 2003). For bulk sediment tests a negative control will be a sediment that is essentially free of contaminants. Such a negative control provides evidence of test organism health, which is in most acute tests defined as mortality lower than 10 %, and for chronic tests a survival of more than 80 % is sufficient. Control sediments can be provided from field-collected sediments or from artificial or formulated sediments. The physicochemical properties such as grain size, TOC and background levels of contaminants should be determined. However, these properties could be different to those of die area studied. 

One such proxy makes use of element ratios. For example, the ratio of Cd to Ca in foraminiferal tests is a proxy for the PO4 content of the past water mass in which the foraminifera formed and therefore provides information on the past thermohaline circulation. This tracer is explained in detail in the article on trace elements in foraminiferal tests. Similarly, the ratio of the intermediate uranium decay products Pa and °Th, measured in bulk sediment, may under certain conditions provide information on the advection of water masses in the overlying water column in the past see Cosmogenic Isotopes and Uranium-Thorium Series Isotopes in Ocean Profiles). Isotope ratios are ideally suited as long-term proxy tracers. Some of these isotope ratios are characteristic of certain seawater properties and... 

The main advantage of these methods is that they can potentially produce a continuous profile of sediment properties that can be correlated witii geophysical data (i.e., bulk density, water content, classification, strength, and compressibility) (Ehlers et al., 2008). However, the effect of the steel drill pipe and the unknown size of the annulus outside the drill pipe obscure the interpretability of the results (Anderson 1985 Pelletier et al., 1997). Detailed information on in situ investigations is presented in Chapter 4. 

Since relatively few common minerals make up the structure of most surficial marine sediments, the bulk elastic properties of particles of a specific sediment type in a given environment are similar the world over, and the inaccuracy of regression equations is less than 1% (Hamilton and Bachman, 1982). Deviations, displayed by the scatter in the... 

This equation defines the Stokes diameter Xstokes on the basis of the density contrast Ap = ps - pm between solid and fluid phase. It should not be confused with the density contrast Ap between the porous particle phase (with Pp.etr) and the fluid. Such a definition might be meaningful for dense agglomerates with defined porosity, which can be measured by nitrogen adsorption (Staiger et al. 2002), or may be deduced from the powder bulk density (Barthel et al. 1998) or from sediment properties (Katzel 2007, pp. 183-187). However, it should be avoided for fractal aggregates, where the concept of uniform porosity fails for several reasons (no defined surface, size-dependent and locally varying porosity). 

The erosion rate data discussed above were measured using quartz particles grouped into size classes with a fairly narrow size distribution, which allowed for examination of the effects of particle size and bulk density on erosion rates. As discussed for the critical shear stress, several other sediment properties also influence the erosion rate, including particle size distribution, ionic strength, mineralogy, gas content, and benthic and bacterial colonization. As a result of the many bulk properties that influence the erodibility of a given sediment, the parameters A, n, and m for Equation... 

EFDC allows the base erosion rate and critical shear stress for erosion to be user-defined constants or predicted values based on sediment properties (i.e., bulk density or void ratio). Selection of the sediment-dependent formulations requires use of the EFDC bed consolidation simulation to predict time and depth variation in these bed properties. The sediment-dependent formulations in EFDC compute a decreasing base erosion rate and increasing critical shear stress with increases in bulk density and associated decreases in the void ratio. 

Basic sediment properties, such as dry bulk density, porosity, and grain size distribution. 

Further development, implementation, and interpretation of devices for in situ measurement of sediment erosion, especially in systems with heterogeneous (cohesive and noncohesive) bottom sediment properties (e.g., grain size distribution, dry bulk density porosity, organic carbon content) and development of submodels for predicting sediment resuspension as a function of more easily measured sediment properties and modeled bottom shear stress. 

Generally, Httle is known in advance concerning the degree of homogeneity of most sampled systems. Uniformity, rarely constant throughout bulk systems, is often nonrandom. During the production of thousands of tons of material, size and shape distribution, surface and bulk composition, density, moisture, etc, can vary. Thus, in any bulk container, the product may be stratified into zones of variable properties. In gas and Hquid systems, particulates segregate and concentrate in specific locations in the container as the result of sedimentation (qv) or flotation (qv) processes. 

As shown in Fig. 3, CHEMGL considers 10 major well-mixed compartments air boundary layer, free troposphere, stratosphere, surface water, surface soil, vadose soil, sediment, ground water zone, plant foliage and plant route. In each compartment, several phases are included, for example, air, water and solids (organic matter, mineral matter). A volume fraction is used to express the ratio of the phase volume to the bulk compartment volume. Furthermore, each compartment is assumed to be a completely mixed box, which means all environmental properties and the chemical concentrations are uniform in a compartment. In addition, the environmental properties are assumed to not change with time. Other assumptions made in the model include continuous emissions to the compartments, equilibrium between different phases within each compartment and first-order irreversible loss rate within each compartment [38]. 

The physical characteristics of sewer deposits can be described in terms of individual particle and bulk properties. The hydraulic and structural conditions in the sewer, together with the nature of the inputs, will control the type of material that deposits at a given location. Crabtree (1989) has proposed a sewer sediment taxonomy that is relevant mainly in terms of physical properties but also to chemical and biological processes (Table 3.5). The taxonomy is based on four primary classes with a fifth class B comprising agglutinated or cemented class A material. 

The octanol-water partition coefficient, Kow, is the most widely used descriptor of hydrophobicity in quantitative structure activity relationships (QSAR), which are used to describe sorption to organic matter, soil, and sediments [15], bioaccumulation [104], and toxicity [105 107J. Octanol is an amphiphilic bulk solvent with a molar volume of 0.12 dm3 mol when saturated with water. In the octanol-water system, octanol contains 2.3 mol dm 3 of water (one molecule of water per four molecules of octanol) and water is saturated with 4.5 x 10-3 mol dm 3 octanol. Octanol is more suitable than any other solvent system (for) mimicking biological membranes and organic matter properties, because it contains an aliphatic alkyl chain for pure van der Waals interactions plus the alcohol group, which can act as a hydrogen donor and acceptor. 

Sediments have the property of absorbing organic contaminants from water within their bulk (accumulation) and, indeed, it has been shown that the concentration, for example, of some types of insecticide in river sediments is some 10000 times greater than occurs in the surrounding water. 

These Early works, mainly for ca. thirty years ago, provided information about the nature and the origin (mainly marine planktonic) and the low degree of diagenetic evolution of this OM. Moreover, all these studies concluded the quantitative importance of extractable HC in the OM associated to phosphorites. But these works were performed on bulk phosphorites. Thus, it seems to us that a comparative study of the specific composition and properties of the OM of pellets and of their surrounding sediments... 

Several models have been proposed to estimate the thermal conductivity of hydrate/gas/water or hydrate/gas/water/sediment systems. The most common are the classical mixing law models, which assume that the effective properties of multicomponent systems can be determined as the average value of the properties of the components and their saturation (volumetric fraction) of the bulk sample composition. The parallel (arithmetic), series (harmonic), or random (geometric) mixing law models (Beck and Mesiner, 1960) that can be used to calculate the composite thermal conductivity (kg) of a sample are given in Equations 2.1 through 2.3. 

Table I Information on sample origin, carbonate content and bulk organic matter properties of sediments from the bituminous laminite series of the Nordlinger Ries (for abbreviations see text). Carbonate content is expressed as CaCC>3. The residue not recoverable from the liquid chromatography column accounts for the remainder of 100%. n.d. = not determined. 

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