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B R Simoneit

Publications and source records attributed to B R Simoneit.

32 records · Page 2Linked to original sources
PubMed1987

Low temperature hydrothermal maturation of organic matter in sediments from the Atlantis II Deep, Red Sea.

Hydrocarbons and bulk organic matter of two sediment cores (No. 84 and 126, CHAIN 61 cruise) located within the Atlantis II Deep have been analyzed. Although the brines overlying the coring areas were reported to be sterile, microbial inputs and minor terrestrial sources the major sedimentary organic material. This input is derived from the upper water column above the brines. Both steroid and triterpenoid hydrocarbons show that extensive acid-catalyzed reactions are occurring in the sediments. In comparison with other hydrothermal (Guaymas Basin) or intrusive systems (Cape Verde Rise), the Atlantis II Deep exhibits a lower degree of thermal maturation. This is easily deduced from the elemental composition of the kerogens and the absence of polynuclear aromatic hydrocarbons of a pyrolytic origin in the bitumen. The lack of carbon number preference among the n-alkanes suggests, especially in the case of the long chain homologs, that the organic matter of Atlantis II Deep sediments has undergone some degree of catagenesis. However, the yields of hydrocarbons are much lower than those observed in other hydrothermal areas. The effect of lower temperature and poor source-rock characteristics appear to be responsible for the differences.

Alkanes↗
PubMedDate not supplied

Application of real-time mass spectrometric techniques to environmental organic geochemistry. I. Computerized high resolution mass spectrometry and gas chromatography-low resolution mass spectrometry.

LOGOS (Smith et al. 1971), an integrated mass spectrometer/computer system, has been employed in a series of experiments which illustrate the utility of the automated techniques of real-time mass spectrometry in the study of organic compounds in the environment. These techniques are shown to be particularly useful in resolving complex mixtures of organic compounds encountered in environmental studies. Complete high resolution mass spectrometry, particularly when used in conjunction with combined gas chromatography/mass spectrometry, and auxiliary techniques such as stable isotopic labeling are described to illustrate the type and scope of information that may be obtained. Illustrative samples include extracts of air- and waterborne particulates, extracts of water-soluble organic material, and a DDT metabolite from sewage sludge.

Air↗
PubMedDate not supplied

High molecular weight polycyclic aromatic hydrocarbons in hydrothermal petroleums from the Gulf of California and Northeast Pacific Ocean.

Hydrothermal petroleums and heavy tars have been analyzed for polycyclic aromatic hydrocarbons (PAH) with molecular weights greater than that of coronene (300 da). Samples from the hydrothermal systems in the Guaymas Basin (Gulf of California) and in the Escanaba Trough and Middle Valley (Northeastern Pacific) were analyzed by gas chromatography-mass spectrometry and high pressure liquid chromatography with diode-array absorbance detection. Mass spectra and fluorescence spectra were used to characterize the compounds. Several large PAHs with six and more rings were identified among the heavy PAH. Production routes via one-ring build-up and Scholl-condensation are proposed to explain the observed structures. The variations in PAH concentrations and distributions between samples from different locales are a consequence of the hydrothermal conditions of generation, migration, and post-depositional alteration.

Gas Chromatography-Mass Spectrometry↗
PubMedDate not supplied

Carbon isotope systematics of individual hydrocarbons in hydrothermal petroleum from Escanaba Trough, northeastern Pacific Ocean.

We submitted individual aliphatic and polycyclic aromatic hydrocarbons in samples of hydrothermal petroleum from Escanaba Trough to compound specific isotope analysis to trace their origins. The carbon isotope compositions of the alkanes and polycyclic aromatic hydrocarbons (means -27.5 and -24.7%, respectively) reflect a primarily terrestrial organic matter source.

Alkanes↗
PubMedDate not supplied

Hydrous pyrolysis of polycyclic aromatic hydrocarbons and implications for the origin of PAH in hydrothermal petroleum.

Polycyclic aromatic hydrocarbons (PAH) are found at high concentrations in thermally altered organic matter and hydrothermally generated petroleum from sediment-covered seafloor hydro-thermal systems. To better understand the factors controlling the occurrence of PAH in thermally altered environments, the reactivities of two PAH, phenanthrene and anthracene, were investigated in hydrothermal experiments. The compounds were heated with water at 330 degrees C in sealed reaction vessels for durations ranging from 1 to 17 days. Iron oxide and sulfide minerals, formic acid, or sodium for-mate were included in some experiments to vary conditions within the reaction vessel. Phenanthrene was unreactive both in water alone and in the presence of minerals for up to 17 days, while anthracene was partially hydrogenated (5-10%) to di- and tetrahydroanthracene. In the presence of 6-21 vol % formic acid, both phenanthrene and anthracene reacted extensively to form hydrogenated and minor methylated derivatives, with the degree of hydrogenation and methylation increasing with the amount of formic acid. Phenanthrene was slightly hydrogenated in sodium formate solutions. The hydrogenation reactions could be readily reversed; heating a mixture of polysaturated phenanthrenes resulted in extensive dehydrogenation (aromatization) after 3 days at 330 degrees C. While the experiments demonstrate that reaction pathways for the hydrogenation of PAH under hydrothermal conditions exist, the reactions apparently require higher concentrations of H2 than are typical of geologic settings. The experiments provide additional evidence that PAH may be generated in hydrothermal systems from progressive aromatization and dealkylation of biologically derived polycyclic precursors such as steroids and terpenoids. Furthermore, the results indicate that PAH initially present in sediments or formed within hydrothermal systems are resistant to further thermal degradation during hydrothermal alteration.

Anthracenes↗
PubMedDate not supplied

Lipid formation by aqueous Fischer-Tropsch-type synthesis over a temperature range of 100 to 400 degrees C.

The formation of lipid compounds during an aqueous Fischer-Tropsch-type reaction was studied with solutions of oxalic acid as the carbon and hydrogen source. The reactions were conducted in stainless steel vessels by heating the oxalic acid solution at discrete temperatures from 100 to 400 degrees C, at intervals of 50 degrees C for two days each. The maximum lipid yield, especially for oxygenated compounds, is in the window of 150-250 degrees C. At a temperature of 100 degrees C only a trace amount of lipids was detected. At temperatures above 150 degrees C the lipid components ranged from C12 to > C33 and included n-alkanols, n-alkanoic acids, n-alkyl formates, n-alkanals, n-alkanones, n-alkanes, and n-alkenes, all with essentially no carbon number preference. The n-alkanes increased in concentration over the oxygenated compounds at temperatures of 200 degrees C and above, with a slight reduction in their carbon number ranges due to cracking. It was also noted that the n-alkanoic acids increased while n-alkanols decreased with increasing temperature above 200 degrees C. At temperatures above 300 degrees C synthesis competes with cracking and reforming reactions. At 400 degrees C significant cracking was observed and polynuclear aromatic hydrocarbons and their alkylated homologs were detected. The results of this work suggest that the formation of lipid compounds by aqueous FTT reactions proceeds by insertion of a CO group at the terminal end of a carboxylic acid functionality to form n-oxoalkanoic acids, followed by reduction to n-alkanoic acids, to n-alkanals, then to n-alkanols. The n-alkenes are intermediate homologs for n-alkan-2-ones and n-alkanes. This proposed mechanism for aqueous FTT synthesis differs from the surface-catalyzed stepwise FT process (i.e., gaseous) of polymerization of methylene reported in the literature.

Alkanes↗