Biogenic silica

Prado Figueroa, M., Barrera, F., Cesaretti, N.N., (2008). Chalcedony (a oystaUine variety of silica) biogenic origin in electric organs from living Psammobatis extenta (family Rajidae). Micron 39,1027-1035. 

MicrocrystaUine Silicas. Various microcrystalline (cryptocrystalline) materials such as flint, chert, and diatomaceous earth are found ia nature (see Diatomite). These may arise from amorphous silica, often of biogenic origin, which undergoes compaction and microcrysta11i2ation over geologic time. 

S. Maim and C. C. Perry, Structural Aspects of Biogenic Silica, Ciba Poundation Symposium 121, John Wiley Sons, Inc., New York, 1986, pp. 40—58. 

Figure 7. Separation of eight biogenic amines using ion pair partition liquid chromatography. Conditions 30 cm column with 4 fim silica stationary phase, 0.1M HClO /0.9M NaClO mobile phase, ethylacetate/tributyl phosphate/hexane (72.5/10/17.5) velocity, 0.8 cm/sec (47).

The role of advection also was shown clearly by Friedrich and Rutgers van der Loeff (2002) in the Southern Ocean, especially when attempting to use °Po as a proxy for the estimation of POC and biogenic silica export. These authors pointed out that the °Pb pair could be used to constrain POC and biogenic silica export fluxes if advection could be properly characterized. 

Resolving some of the issues surrounding the use of " Th as a tracer for POC flux, as well as collecting simultaneous °Po and °Pb data, will enable a better characterization of other components of the particulate flux, such as biogenic silica (Buesseler et al. 2001 Friedrich and Rutgers van der Loeff 2002) and particle-associated... 

Buesseler KO, Ball L, Andrews J, Cochran JK, Hirschberg DJ, Bacon MP, Fleer A, Brzezinski M (2001) Upper ocean export of particulate organic caibon and biogenic silica in the Southern Ocean along 170°W. Deep-Sea Res II 48 4275-4297... 

Coradin, T. and Lopez, P.J. (2003) Biogenic silica patterning simple chemistry or subtle biology ChemBioChem, 4, 251—255. 

Lopez, P.J., Gautier, C., Livage, J. and Coradin, T. (2005) Mimicking biogenic silica nanostructures formation. Current Nanoscience, 1, 73—83. 

On the other hand, gas chromatographic methods may overestimate the concentration of total petroleum hydrocarbons in a sample due to the detection of nonpetroleum compounds. In addition, cleanup steps do not separate petroleum hydrocarbons perfectly from biogenic material such as plant oils and waxes, which are sometimes extracted from vegetation-rich soil. Silica gel cleanup may help to remove this interference but may also remove some polar hydrocarbons. 

Samples are extracted with a suitable solvent (i.e., a solvent with no C-H bonds), and biogenic polar materials are removed with silica gel. Some polar petroleum constituents may be removed as part of the silica gel cleanup. The absorbance of the silica gel eluate is measured at the specified frequency and compared to the absorbance of a standard or standards of known petroleum... 

In the method(s), petroleum constituents are extracted into a suitable solvent. Biogenic polar materials typically may be partially or completely removed with silica gel. The solvent is evaporated and the residue is weighed. This quantity is reported as a percentage of the total soil sample dry weight. These methods are better suited for heavy oil because they include an evaporation step. 

The clay minerals of aeolian origin comprise 25 to 75% of the mass of pelagic sediments. The large range in composition reflects the latitudinal nature of the dust belt as well as dilution by other locally important particle types such as clay minerals of volcanogenic origin and biogenic hard parts (calcite and opaline silica). 

D. Cwienk, G. R. Heath, R E. Biscaye, V. Kolia, J. Thiede, and J. P. Dauphin (1986). Distribution of biogenic silica and quartz in recent deep-sea sediments. Geology, 14, 199-203. 

A global map of quartz abundance is given in Figure 14.12. In this case, the contribution of quartz is presented as the contribution to the bulk sediment from which biogenic carbonate and silica have been removed. This map is very similar to the global distribution of dust presented in Figure 11.4, reflecting the importance of aeolian transport for this detrital silicate. 

Preservation versus Dissolution of Sinking Detrital Biogenic Silica... 

PRESERVATION VERSUS DISSOLUTION OF SINKING DETRITAL BIOGENIC SILICA... 

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