Other sediments

Deep sea sediments may contain magnetite which may be not only of detrital origin, but may also contain a contribution from former magnetotactic bacteria. Petersen et al. (1986) have identified single-domain, magnetite crystals in Eocene to Quaternary sediments from the South Atlantic, which are very similar to biomagnetite in recent marine bacteria (see Chap. 17). 

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Other Sedimentation Seale-Up Equations. Some centrifuge supphers use an area-equivalent, description instead of S others use KQ or values. All of these ate in urhts of area. For a disk centrifuge,... 

Density Variation Gravimetric HYDROMETER METHOD Ths suspension of a powder is prepd as for other sedimentation... 

Organotin levels of the sediments, especially in tributyltin, are found to be very high compared with those of waters. It has been shown that Bu3Sn+, like other organometallics, is adsorbed rapidly by marine and other sediments. The sediment therefore represents a sink for Bu3Sn+ leached from the antifouling coating of boats. 

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. 

A less direct effect of sedimentation is the tendency of particles of sand, silt, mud, clay, and other sediments to adsorb pesticides, bacteria, toxic metals, and other harmful substances. The U.S. Environmental Protection Agency has estimated that of the 300 million cubic yards (228 million cubic meters) dredged in the United States each year, up to 12 million cubic yards (9 million cubic meters) are so badly contaminated that they require special handling. 

Lie de vin oil (green cognac oil or wine lees oil) is obtained by steam distillation of the yeast and other sediments (lees) formed in wine. It is a green to bluish-green liquid with a characteristic cognac aroma. 

It is interesting to compare these observed BSAFi]ipoc values (Table 10.3) with values reported for other sediment-dwelling organisms and/or locations. Tracey and Hansen (1996) have compiled numerous BSAFaipoc data for PCBs and some data for polycyclic aromatic hydrocarbons (PAHs). The reported BSAF,ripoc values for PCBs... 

H -Cation Exchange. This section summarizes the results of laboratory analyses performed on LRL sediments to measure the total, organically bound, and exchangeable concentrations of base cations contained therein. We discuss mineral weathering and decomposition of organic matter with respect to the production of cations and estimate the possible contribution of H+ -cation exchange to water-column chemistry and the generation of alkalinity (IAG). Other sediment processes that may influence interpretation of data, such as bioturbation, are also discussed. 

Olivine crystallizes from magmas that are rich in magnesia and low in silica and which form such rocks as gabbros, norites, peridotites and basalts. The metamorphism of impure dolomites or other sediments in which the magnesia content is high and silica low seems to produce olivine. 

Ribonuclease IV purified from an RNase I minus strain of E. coli (MRE-600) specifically cleaves R17 RNA into two large fragments, one sedimenting at about 15 S carrying the 5 terminal of the original molecule, and the other sedimenting at about 21 S (131). The nature of the bonds cleaved by the enzyme is not known. 

Sediment stratigraphy controls the hydrate distribution at Hydrate Ridge. The methane-rich migration pathway of Horizon A provides enriched hydrate formation relative to other sediments. In Figure 7.26, the remote sensing logs (gamma ray, density, RAB, and Archie water saturation) are most sensitive to hydrates. 

The weathering of surface rocks has had a critical role in the chemical evolution of the continental crust for most of the Earth s history. In the presence of air and water, mafic minerals tend to rapidly weather into iron (oxy)(hydr)oxides, clays, and other silicate minerals, and at least partially water-soluble salts of alkalis (sodium and potassium) and alkaline earths (calcium and magnesium). In contrast, quartz in felsic and intermediate igneous rocks is very stable in the presence of surface air and water, which explains why the mineral readily accumulates in sands and other sediments. 

Loess refers to deposits of fine-grained wind-blown (eolian) sediments, which may accumulate up to 100 m thick. The material mostly consists of silt grains with perhaps 5-30% clay-sized particles and 5-10% sand (Benn and Evans, 1998), 291. Like other sediments, loess may contain considerable arsenic depending on the chemistry of its source rocks (Table 3.15). 

Just as with the other sediment assemblages, the Middle Pleistocene is represented by only sporadic localities that have survived only in special karstic formations (Tarkd-Uppony-Hilton-Solymar-Siitto, etc.). 

Below Unit B a silty sand layer (Unit C) was encountered in the cores taken between the mouth of the Great Wadi and the center of the Kom el Ahmr. Unit C contained a sequence of Old Kingdom to late Predynastic artifacts dating from about 2500 B.C. to 3200 B.C. Below Unit C, a very compact, well-sorted thick layer of Nile clay and sand was encountered (Unit N). No cores or trenches reached below this sedimentary deposit. Unit N contained occasional Predynastic ceramic and flint artifacts. Samples were collected from each 10-15-cm auger cut within each sedimentary unit in each core or trench. In addition, numerous samples of the Neonile deposits and other sediments from the nearby low desert and Great Wadi were taken for analysis. 

Sedimentation columns (ICI, BCURA) have also been described in which the sediment is extracted, dried and weighed. A full description of these and other sedimentation columns may be found in [ I ]... 

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