Compounds biogenic

Thermoanalysis methods such as pyrolysis-gas chromatography-mass spectrometry [GC-MS] and thermogravimetry mass spectrometry have been used to characterise hydrocarbon sludges from petrochemical plants and polluted soils [26,27]. In combination with conventional extraction and supercritical fluid extraction followed by [ GC-MS ], over 100 constituents were identified in samples. White et al. [28] also applied pyrolysis-[GC-MS] to the determination of hydrocarbons and showed that the analysis can be complicated by the presence of natural organic matter. White [28] inferred the presence of biogenic compounds in Alaskan soil. 

Gagosian R. B. and Stuermer D. H. (1977) The cycling of biogenic compounds and their diagenetically altered transformation products in seawater. Mar. Chem. 5, 605-632. 

Soil DOM comprises a wide variety of organic substances. Specific microbial or plant exudates are released as a consequence of metabolic activity of soil biota. Transformations of biogenic compounds, through partial degradation and polymerization, result in the formation of a structurally ill-defined mixture of humic substances, a term used to include both humic and fulvic acids (20, 21). Nonuniform effects of DOM components on metal mobilization may be anticipated because of the heterogeneity of their chemical structures and properties. 

Precursors of membrane components, carbohydrates, amino acids, and other biogenic compounds formed either directly or indirectly from those chiral and non-chiral molecules delivered to Earth. Benzene, for instance, is one of the aromatic compounds of interstellar dust from which a precursor of the membrane lipid inositol-1-phosphate apparently derived by oxidation in a long series of chemical reactions. The structure of the important lipid, a derivative of inositol-phosphate in Fig. 6.1, displays two different fatty acid side chains (marked in blue and green) that frequently occur in membranes. 

The structural unit of the phosphoglycerides is D-glycerol-3-phosphate, a derivative of the trivalent alcohol glycerol. The compounds glycerol and di-hydroxy-acetone were detectable in the Murchison meteorite. This does seem noteworthy as these biogenic compounds are not in the products of the prebiotic soup. What is the mechanism of lipid formation in meteorites This question has not been answered. 

The FeS world is a still incomplete model for building up a primitive metabolism and other pathways to enlarge the repertoire of biogenic compounds. Although limited because of the missing enantiomeric amino acids, any FeS scenario is open-ended... 

Apart from these obviously biogenic compounds only very few definite anthropogenic substances were identified. Within the group of xenobiotics 2,4 - and 4,4 -dichlorophenylmethane, DDT-derived metabolites, were most abundant. A pyrolytic conversion of related DDT metabolites to DDM cannot be excluded. Thus the occurrence of DDM in the pyrogram is only suggestive for DDT group metabolites in general. 

Depending on the degradation method a variety of biogenic compounds was identified reflecting the natural contribution to the MOM. Dominating groups of substances are illustrated in Fig. 4. 

A great variety of organic compounds are emitted by vegetation. These biogenic compounds are highly reactive in the atmosphere. They are basically alkenes or cycloalkenes, and their atmospheric chemistry is generally analogous to that of alkenes. Because of the presence of C=C double bonds these molecules are susceptible to attack by 03 and N03, in addition to the customary reaction with OH radicals. 

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