Sedimentation conditions

An analytical ultracentrifugation method for determining the molecular mass, diffusion coefficient, and/or state of oligomerization of a macromolecule by conducting sedimentation conditions to establish an equilibrium distribution of the macromolecule from the meniscus to the bottom of the observation cell. 

The first one is to the South of the 1 Karaiaz borehole, at the area of Upper Eocene sediments spreading. The aim would be a precise identification of the Upper Eocene sediment conditions in one section with seismic survey data. 

Field-collected sample of presumably clean (uncontaminated) sediment, selected for properties (e.g., particle size, compactness, total organic content) representing sediment conditions that closely match those of the sample(s) of test sediment except for the degree of chemical contaminants. It is often selected from a site that is uninfluenced or minimally influenced by the source(s) of anthropogenic contamination but within the general vicinity of the site(s) where samples of test sediment are collected. A reference sediment should not produce a toxic effect (or have a minimum effect) on a test species. A sample of reference sediment should be included in each series of toxicity tests with test sediment(s). See also Artificial sediment, Positive control sediment and Test sediment. Volume 1(2,13), Volume 2(8). 

In the hard kaolinites there is a positive correlation between mica and books which Hinckley suggests may be due, in part, to sedimentation conditions which favored the simultaneous deposition of books and mica in preference to quartz. This type also has Ti02 positively related to crystallinity. Crystallinity increases as grain size increases. This may reflect a leaching process in which quartz, Fe203 and montmorillonite are removed, Ti02 is concentrated as anatase, and some authigenic kaolinite is formed. 

The primary abiotic and biological processes that transform uranium in soil are oxidation-reduchon reactions that convert U(VI) (soluble) to U(IV) (insoluble). Reduction of U(VI) to U(IV) can occur as a result of microbial action under anaerobic soil or sediment conditions, thereby reducing the mobility of uranium in its matrix (Barnes and Cochran 1993 Francis et al. 1989). Further abiotic and biological processes that can transform uranium in the environment are the reactions that form complexes with inorganic and organic ligands (see Section 5.3.1). 

In these examples as well as for most aquatic sediments, the principal diagenetic reactions that occur in these sediments are aerobic respiration and the reduction of Mn and Fe oxides. Under the slower sedimentation conditions in natural lakes and estuaries, there is sufficient time (years) for particulate organic matter to decompose and create a diagenetic environment where metal oxides may not be stable. When faster sedimentation prevails, such as in reservoirs, there is less time (months) for bacteria to perform their metabohc functions due to the fact that the organisms do not occupy a sediment layer for any length of time before a new sediment is added (Callender, 2000). Also, sedimentary organic matter in reservoir sediments is considerably more recalcitrant than that in natural lacustrine and estuarine sediments as reservoirs receive more terrestrial organic matter (Callender, 2000). 

Table 3 lists the predominant microorganisms in both DNA and RNA profiles for the control batch at T=0. Both DNA and RNA analysis of the nitrate microcosm at T=3 days showed substantial shifts in community composition (Table 4), with Arcobacter sp. dominating in both cases. Arcobacter sp. are known as nitrate reducers since they play a role in nitrogen fixation, so this shift is consistent with sediment conditions. A couple of additional nitrate-reducing bacteria. Pseudomonas sp. and Nisaea denitrificans, were also identified. 

A wide variation of IQ values have been published in the literature for Sr2 sorption (NCRP 1984) that reflect differences in soil and sediment conditions as well as the analytical techniques used (Bunde et al. 1997). IQ values of 15-40 L/kg were measured for 90Sr2+ in aquifer sediments near Liquid Waste Disposal Facilities at the Hanford site in Washington, where rapid ion exchange dominates (DOE 1996d). IQ was... 

The present-day overall distribution of the Paleozoic shales (Ordovician, Silurian, Early Devonian) was determined by the sedimentation conditions and by the rate of Hercynian erosion of various units in the region. Over the geological history, the thickest Paleozoic shales were localized in the south, south-west and west of the region. Here the primary thickness was at a maximum, whereas the Hercynian erosion rate was at its minimum. At present, the overall thickness of shale beds is 600-700 m in the south, 280-660 m in the west, and 220-460 m at the center (see Figs. 5.1,5.2). 

Using Eh-pH diagram for particular metal and measured soil pH and redox (Eh) condition, we can obtain an estimate of the metal species present under a specific set of soil or sediment conditions. Some of the most comprehensive data detailing Eh-pH diagram for elements can be obtained in the studies by Pourbaix (1966), Garrels and Christ (1965), Krauskopf (1979), Berner (1971), and Stumm and Morgan (1981). 

Under what sediment condition is cadmium soluble ... 

Yussoff, E.M., Matias, H.B. and Shariff, M. Phytoplankton communities and shrimp production in culture ponds with different water and sediment conditions. Sixth Asian Fisheries Forum Book of Abstracts, p. 300, 2001. 

Heparin/Nuclear Protein Ratio Buffer Ionic Strength Sedimentation Conditions... 

---