Distribution and sources of lipid compound series in sediment cores of the southern South China Sea.

Three short sediment cores from inner continental shelf of the southern South China Sea (5-50 km) off Terengganu were analyzed for lipid contents (i.e., homologous aliphatic compounds and sterols) using gas chromatography-mass spectrometry. The concentrations of the total aliphatic hydrocarbons (TAHs) ranged from 0.152 to 6.91 µg/g dry weight. The n-alkane distribution was from nC13 to nC36, with a carbon preference index (CPI13₋35) from 1.08 to 4.28 and a carbon number maximum (Cmax), depending on a sample, at 31 or 18. In addition, a strong odd-to-even carbon number predominance was observed in nC25-nC35 range. The distribution of the n-alkanoic acids and n-alkanols in all samples exhibited an even-to-odd carbon number predominance and ranged from C10 to C26 and from C12 to C34, respectively. The n-alkanols were dominated by the long-chain homologs with Cmax at 22; on the other hand, the n-alkanoic acid distributions showed a predominance of short-chain homologs with a Cmax at 16. The total sterol concentrations ranged from 0.41 to 3.57 µg/g dry weight. Cholesterol was most abundant at the offshore stations, whereas sitosterol was dominant at near-shore station. Pentacyclic triterpenoids such as friedelin and taraxerol α- and ß-amyrins, which are known biomarkers for higher plants, were detected at all stations with a dilution trend offshore. In conclusion, the marine sediments off southern Terengganu can still be considered uncontaminated, where the compound sources are biogenic from terrestrial plants superimposed with a marine productivity input.

Biomass burning as the main source of organic aerosol particulate matter in Malaysia during haze episodes.

The haze episodes that occurred in Malaysia in September-October 1991, August-October 1994 and September-October 1997 have been attributed to suspended smoke particulate matter from biomass burning in southern Sumatra and Kalimantan, Indonesia. In the present study, polar organic compounds in aerosol particulate matter from Malaysia are converted to their trimethylsilyl derivatives and analyzed by gas chromatography-mass spectrometry in order to better assess the contribution of the biomass burning component during the haze episodes. On the basis of this analysis, levoglucosan was found to be the most abundant organic compound detected in almost all samples. The monosaccharides, alpha- and beta-mannose, the lignin breakdown products, vanillic and syringic acids and the minor steroids, cholesterol and beta-sitosterol were also present in some samples. The presence of the tracers from smoke overwhelmed the typical signatures of emissions from traffic and other anthropogenic activities in the urban areas.

Air quality model evaluation data for organics. 6. C3-C24 organic acids.

The atmospheric concentrations of 47 carboxylic acids in the semivolatile and particle phases are quantified in the Los Angeles area, as part of a larger study of the vapor-phase, semivolatile, and particle-phase organic compounds. Variations in the spatial and temporal distributions of acid concentrations are analyzed to determine whether atmospheric formation or primary emissions are responsible for the observed levels. Relatively low molecular weight aliphatic dicarboxylic acids (e.g., butanedioic acid, hexanedioic acid, and propanedioic acid) and some n-alkanoic acids (e.g., n-octanoic acid and n-nonanoic acid) are found at an offshore sampling location at levels comparable to urban area concentrations indicating that these compounds or their atmospheric precursors may be derived from long-range transport or natural background sources. Some aromatic carboxylic acids (e.g., benzoic acid and 1,2-benzenedicarboxylic acid) have spatial and temporal distributions suggesting that formation from anthropogenic emissions of gaseous precursors dominates their atmospheric concentrations. Additionally, the distributions of aliphatic carboxylic acid concentrations known to be emitted from primary sources (e.g., hexadecanoic acid and octadecanoic acid) are consistent with direct emissions as the dominant source of these compounds.

Persephonella marina gen. nov., sp. nov. and Persephonella guaymasensis sp. nov., two novel, thermophilic, hydrogen-oxidizing microaerophiles from deep-sea hydrothermal vents.

Two thermophilic, strictly chemolithoautotrophic, microaerophilic, hydrogen-oxidizing members of the Bacteria designated strain EX-H1T and strain EX-H2T were isolated from two separate deep-sea hydrothermal vent sites at 9 degrees N 104 degrees W in the Pacific Ocean and Guaymas Basin. The motile 2-4-microm-long rods were Gram-negative and non-sporulating. The temperature range for growth was between 55 and 80 degrees C for EX- H1T (optimum at 73 degrees C) and 55-75 C for EX-H2T (optimum at 70 C). Both strains grew fastest at 2.5% (w/v) NaCl and at pH 6, although growth was observed from pH 4.7 to pH 7.5. EX-H1T and EX-H2T were able to use elemental sulfur, thiosulfate or hydrogen as an electron donor, and oxygen (2-3%, v/v) or nitrate as an electron acceptor. EX-H1T was also able to use elemental sulfur as an electron acceptor. EX-H1T and EX-H2T further differed in their genomic G+C content (38.5 and 37.4 mol%, respectively) and 16S rRNA sequences (4% difference). Maximum-likelihood analysis of the 16S rRNA phylogeny placed both isolates within the Aquificales as a distinct lineage and showed them to be only about 85% similar to Aquifex pyrophilus. On the basis of phenotypic and phylogenetic characteristics, it is proposed that EX-H1T and EX-H2T belong to a new genus within the Aquificales, namely Persephonella gen. nov. It is further proposed that EX-H1T be named Persephonella marina sp. nov., the type species of the genus, and that EX-H2T be named Persephonella guaymasensis sp. nov., a second species in this genus.

Detecting organic tracers from biomass burning in the atmosphere.

This is a brief review key to the literature on the determination of organic tracers from biomass burning which are detectable even after long-range global transport in total extracts of atmospheric particles. The major tracers are thermal degradation products from the biopolymer cellulose, namely the didehydromonosaccharide derivatives levoglucosan, galactosan and mannosan and the resin acid derivative dehydroabietic acid, with minor beta-sitosterol. Dehydroabietic acid is emitted primarily from burning of conifer fuel and these tracers are found in most aerosol samples from the North American continent. Particulate matter from the atmosphere over oceanic areas contains organic tracers from both natural and biomass burning emissions. The major biomarker compounds characterized are natural products from continental vegetation consisting primarily of epicuticular wax components and trace components from biomass burning emissions. The presence of these tracers in atmospheric particulate matter over the ocean confirms the long-range transport of smoke from biomass burning off the continents.

Bile acids and sterols in urban sewage treatment plants.

The composition of bile acids, sterols and sterones in water and sludge from an urban sewage treatment plant has been examined for assessment of the possible use of these compounds as pollution biomarkers. Samples were solvent-extracted, hydrolysed, and fractionated by column chromatography to separate acids, hydrocarbons, sterones and sterols. These fractions, except hydrocarbons, were methylated (acids only) and silylated for instrumental analysis. Gas chromatographic-mass spectrometric analysis was performed in the electron-impact mode, using a non-polar capillary column. Lithocholic acids (3alpha- and 3beta-epimers), coprostanone, coprostanol, cholesterol, cholestenone, and cholestanone were found in sludge and all waters. However, the waters after secondary plant treatment contained mainly lithocholic acids epimers and coprostanone, pointing to these compounds as potential markers for urban treatment plant effluents in natural waters courses.

Chemical characterization of fine particle emissions from fireplace combustion of woods grown in the northeastern United States.

A series of source tests was conducted to determine the chemical composition of fine particle emissions from the fireplace combustion of six species of woods grown in the northeastern United States: red maple, northern red oak, paper birch, eastern white pine, eastern hemlock, and balsam fir. Results include fine particle emission rates for total mass, organic and elemental carbon, ionic species, elemental species including potassium, and over 250 specific organic compounds. The data are intended for use in source-apportionment studies that utilize particulate organic compounds as source-specific tracers. The cellulose pyrolysis product levoglucosan was quantified in each of the wood smokes studied and is thus a good candidate as a molecular tracer for wood combustion in general. Differences in emission rates of specific substituted phenols and resin acids can be used to distinguish between the smoke produced when burning hardwoods versus softwoods. Certain organic compounds, such as betulin from paper birch combustion and juvabione and dehydrojuvabione from balsam fir combustion, are unique to those species and can potentially be utilized to trace particulate emissions back to a specific geographical region where those individual tree species are used for firewood.

Highly polar organic compounds present in wood smoke and in the ambient atmosphere.

Fine particulate matter emitted during wood combustion is known to contribute a significant fraction of the total fine aerosol concentration in the atmosphere of both urban and rural areas. In the present study, additional organic compounds that may act as wood smoke tracers in the atmosphere are sought. Polar organic compounds in wood smoke fine particulate matter are converted to their trimethylsilyl derivatives and analyzed by gas chromatography/mass spectrometry. Silylation enables the detection of n-alkanols, plant sterols, and a number of compounds derived from wood lignin that have not previously been reported in wood smoke samples, as well as levoglucosan and related sugar anhydrides formed during the combustion of cellulose. The concentrations of these compounds measured in source emissions are compared to the concentrations in atmospheric fine particle samples collected at a rural background site and at two urban sites in California's San Joaquin Valley. On the basis of this analysis, the sugar anhydrides galactosan and mannosan can be listed along with levoglucosan as being among the most abundant organic compounds detected in all samples.

Measurement of emissions from air pollution sources. 3. C1-C29 organic compounds from fireplace combustion of wood.

Organic compound emission rates for volatile organic compounds (VOC), gas-phase semivolatile organic compounds, and particle-phase organic compounds are measured from residential fireplace combustion of wood. Firewood from a conifer tree (pine) and from two deciduous trees (oak and eucalyptus) is burned to determine organic compound emissions profiles for each wood type including the distribution of the alkanes, alkenes, aromatics, polycyclic aromatic hydrocarbons (PAH), phenol and substituted phenols, guaiacol and substituted guaiacol, syringol and substituted syringols, carbonyls, alkanoic acids, resin acids, and levoglucosan. Levoglucosan is the major constituent in the fine particulate emissions from all three wood types, contributing 18-30% of the fine particulate organic compound emissions. Guaiacol (2-methoxyphenol), and guaiacols with additional substituents at position 4 on the molecule, and resin acids are emitted in significant quantities from pine wood combustion. Syringol (2,6-dimethoxyphenol) and syringols with additional substituents at position 4 on the molecule are emitted in large amounts from oak and eucalyptus firewood combustion, but these compounds are not detected in the emissions from pine wood combustion. Syringol and most of the substituted syringols are found to be semivolatile compounds that are present in both the gas and particle phases, but two substituted syringols that have not been previously quantified in wood smoke emissions, propionylsyringol and butyrylsyringol, are found exclusively in the particle phase and can be used to help trace hardwood smoke particles in the atmosphere. Benzene, ethene, and acetylene are often used as tracers for motor vehicle exhaust in the urban atmosphere. The contribution of wood smoke to the ambient concentrations of benzene, ethene, and acetylene could lead to an overestimate of the contribution of motor vehicle tailpipe exhaust to atmospheric VOC concentrations.

Exploratory studies of PM10 receptor and source profiling by GC/MS and principal component analysis of temporally and spatially resolved ambient samples.

For a recent exploratory study of particulate matter (PM) compositions, origins, and impacts in the El Paso/Juarez (Paso del Norte) airshed, the authors relied on solvent extraction (SX)-gas chromatography/mass spectrometry (GC/MS) procedures to characterize 24-hr quartz fiber (QF) filter samples obtained from nine spatially distributed high-volume (Hi-Vol) PM10 samplers as well as on thermal desorption (TD)-GC/MS methods to characterize 45 time-resolved (2-hr) filter samples obtained with modified 1-m3/hr PM10 samplers. Principal component analysis and related chemometric techniques were used for data reduction and data fusion as well as for multiway data correlation. A high degree of correspondence (R2 = 0.821) was found between the rapid TD-GC/MS method (which can be carried out on 2-hr filter slices containing only microgram amounts of sample) and conventional SX-GC/MS procedures. The four main source patterns of organic PM components observed in GC/MS profiles of both temporally and spatially resolved receptor samples obtained in the El Paso/Juarez border airshed during the study period are interpreted to represent (1) vehicular emissions plus resuspended urban dust; (2) biomass combustion; (3) native vegetation detritus and resuspended agricultural dust; and (4) waste burning. Moreover, principal component analysis of combined, variance-weighted, temporally resolved TD-GC/MS data and spatially resolved SX-GC/MS data was used to determine approximate source locations for specific PM components identified in time-resolved receptor sample profiles. The same approach can be used to determine approximate circadian concentration profiles of specific PM components identified in spatially resolved receptor sample profiles.

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.

Hydrothermal petroleum from lacustrine sedimentary organic matter in the East African Rift.

Cape Kalamba oil seeps occur at the south end of the Ubwari Peninsula, at the intersection of faults controlling the morphology of the northern basin of the Tanganyika Rift, East Africa. Oil samples collected at the surface of the lake 3-4 km offshore from Cape Kalamba have been studied. The aliphatic hydrocarbon and biomarker compositions, with the absence of the typical suite of polynuclear aromatic hydrocarbons, indicate an origin from hydrothermal alteration of immature microbial biomass in the sediments. These data show a similarity between a tar sample from the beach and the petroleum from the oil seeps, and confirm that the source of these oils is from organic matter consisting mainly of bacterial and degraded algal biomass, altered by hydrothermal activity. The compositions also demonstrate a < 200 degrees C temperature for formation/generation of this hydrothermal petroleum, similar to the fluid temperature identified for the Pemba hydrothermal site located 150 km north of Cape Kalamba. The 14C age of 25.6 ka B.P. obtained for the tar ball suggests that Pleistocene lake sediments could be the source rock. Hydrothermal generation may have occurred slightly before 25 ka B.P., during a dry climatic environment, when the lake level was lower than today. These results also suggest that the Cape Kalamba hydrothermal activity did not occur in connection with an increased flux of meteoric water, higher water tables and lake levels as demonstrated in the Kenya Rift and for the Pemba site. Hydrothermal petroleum formation is a facile process also in continental rift systems and should be considered in exploration for energy resources in such locales.

Amino acid abundances and stereochemistry in hydrothermally altered sediments from the Juan de Fuca Ridge, northeastern Pacific Ocean.

The Juan de Fuca Ridge is a hydrothermally active, sediment covered, spreading ridge situated a few hundred kilometres off the west coast of North America in the northeastern Pacific Ocean. Sediments from seven sites drilled during the Ocean Drilling Program (ODP) Legs 139 and 168 were analyzed for total hydrolyzable amino acids (THAA), individual amino acid distributions, total organic C (TOC) and total N (TN) contents. The aim was to evaluate the effects of hydrothermal stress on the decomposition and transformation of sedimentary amino acids. Hydrolyzable amino acids account for up to 3.3% of the total organic C content and up to 12% of the total N content of the upper sediments. The total amounts of amino acids decrease significantly with depth in all drilled holes. This trend is particularly pronounced in holes with a thermal gradient of around 0.6 degrees C/m or higher. The most abundant amino acids in shallow sediments are glycine, alanine, lysine, glutamic acid, valine and histidine. The changes in amino acid distributions in low temperature holes are characterized by increased relative abundances of non-protein beta-alanine and gamma-aminobutyric acid. In high temperature holes the amino acid compositions are characterized by high abundances of glycine, alanine, serine, ornithine and histidine at depth. D/L ratios of samples with amino acid distributions similar to those found in acid hydrolysates of kerogen, indicate that racemization rates of amino acids bound by condensation reactions may be diminished.

Lipid synthesis under hydrothermal conditions by Fischer-Tropsch-type reactions.

Ever since their discovery in the late 1970's, mid-ocean-ridge hydrothermal systems have received a great deal of attention as a possible site for the origin of life on Earth (and environments analogous to mid-ocean-ridge hydrothermal systems are postulated to have been sites where life could have originated or Mars and elsewhere as well). Because no modern-day terrestrial hydrothermal systems are free from the influence of organic compounds derived from biologic processes, laboratory experiments provide the best opportunity for confirmation of the potential for organic synthesis in hydrothermal systems. Here we report on the formation of lipid compounds during Fischer-Tropsch-type synthesis from aqueous solutions of formic acid or oxalic acid. Optimum synthesis occurs in stainless steel vessels by heating at 175 degrees C for 2-3 days and produces lipid compounds ranging from C2 to > C35 which consist of n-alkanols, n-alkanoic acids, n-alkenes, n-alkanes and alkanones. The precursor carbon sources used are either formic acid or oxalic acid, which disproportionate to H2, CO2 and probably CO. Both carbon sources yield the same lipid classes with essentially the same ranges of compounds. The synthesis reactions were confirmed by using 13C labeled precursor acids.

Abiotic formation of hydrocarbons and oxygenated compounds during thermal decomposition of iron oxalate.

The formation of organic compounds during the decomposition of iron oxalate dihydrate (IOD) was investigated as a possible analog for abiotic organic synthesis in geological systems. After heating at 330 degrees C for 2-4 days, IOD decomposed to a mixture of the minerals siderite and magnetite plus gas and non-volatile organic compounds. The organic products included an extremely large variety of compounds, making identification of individual reaction products difficult. However, the non-volatile products were dominated by several homologous series of alkylated cyclic compounds mostly containing a single aromatic ring, including alkylphenols, alkylbenzenes, alkyltetrahydronaphthols, and alkyltetrahydronaphthalenes. Traces of n-alkanols, n-alkanoic acids, n-alkanones, and n-alkanes were also identified. Carbon in the gas phase was predominantly CO2 (+CO?), with lesser amounts of light hydrocarbons to > C6 including all possible branched and normal isomers of the alkanes and alkenes. The organic products were apparently the result of two concurrent reaction processes: (1) condensation of the two-carbon units present in the initial oxalate moiety, and (2) Fischer-Tropsch-type synthesis from CO2 or CO generated during the experiment. Compounds produced by the former process may not be characteristic of synthesis from the single-carbon precursors which predominate in geologic systems, suggesting iron oxalate decomposition may not provide a particularly suitable analog for investigation of abiotic organic synthesis. When water was included in the reaction vessels, CO2 and traces of methane and light hydrocarbon gases were the only carbon products observed (other than siderite), suggesting that the presence of water allowed the system to proceed rapidly towards equilibrium and precluded the formation of metastable organic intermediates.

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.

A review of biomarker compounds as source indicators and tracers for air pollution.

An overview of the application of organic geochemistry to the analysis of organic matter on aerosol particles is presented here. This organic matter is analyzed as solvent extractable bitumen/ lipids by gas chromatography-mass spectrometry. The organic geochemical approach assesses the origin, the environmental history and the nature of secondary products of organic matter by using the data derived from specific molecular analyses. Evaluations of production and fluxes, with cross-correlations can thus be made by the application of the same separation and analytical procedures to samples from point source emissions and the ambient atmosphere. This will be illustrated here with typical examples from the ambient atmosphere (aerosol particles) and from emissions of biomass burning (smoke). Organic matter in aerosols is derived from two major sources and is admixed depending on the geographic relief of the air shed. These sources are biogenic detritus (e.g., plant wax, microbes, etc.) and anthropogenic particle emissions (e.g., oils, soot, synthetics, etc.). Both biogenic detritus and some of the anthropogenic particle emissions contain organic materials which have unique and distinguishable compound distribution patterns (C(14)-C(40)). Microbial and vascular plant lipids are the dominant biogenic residues and petroleum hydrocarbons, with lesser amounts of the pyrogenic polynuclear aromatic hydrocarbons (PAH) and synthetics (e.g., chlorinated compounds), are the major anthropogenic residues. Biomass combustion is another important primary source of particles injected into the global atmosphere. It contributes many trace substances which are reactants in atmospheric chemistry and soot paniculate matter with adsorbed biomarker compounds, most of which are unknown chemical structures. The injection of natural product organic compounds into smoke occurs primarily by direct volatilization/steam stripping and by thermal alteration based on combustion temperature. Although the molecular composition of organic matter in smoke particles is highly variable, the molecular tracers are generally still source specific. Retene has been utilized as a tracer for conifer smoke in urban aerosols, but is not always detectable. Dehydroabietic acid is generally more concentrated in the atmosphere from the same emission sources. Degradation products from biopolymers (e.g., levoglucosan from cellulose) are also excellent tracers. An overview of the biomarker compositions of biomass smoke types is presented here. Defining additional tracers of thermally-altered and directly-emitted natural products in smoke aids the assessment of the organic matter type and input from biomass combustion to aerosols. The precursor to product approach of compound characterization by organic geochemistry can be applied successfully to provide tracers for studying the chemistry and dispersion of ambient aerosols and smoke plumes.

Biomarkers as tracers for life on early earth and Mars.

Biomarkers in geological samples are products derived from biochemical (natural product) precursors by reductive and oxidative processes (e.g., cholestanes from cholesterol). Generally, lipids, pigments and biomembranes are preserved best over longer geological times and labile compounds such as amino acids, sugars, etc. are useful biomarkers for recent times. Thus, the detailed characterization of biomarker compositions permits the assessment of the major contributing species of extinct and/or extant life. In the case of the early Earth, work has progressed to elucidate molecular structure and carbon isotropic signals preserved in ancient sedimentary rocks. In addition, the combination of bacterial biochemistry with the organic geochemistry of contemporary and ancient hydrothermal ecosystems permits the modeling of the nature, behavior and preservation potential of primitive microbial communities. This approach uses combined molecular and isotopic analyses to characterize lipids produced by cultured bacteria (representative of ancient strains) and to test a variety of culture conditions which affect their biosynthesis. On considering Mars, the biomarkers from lipids and biopolymers would be expected to be preserved best if life flourished there during its early history (3.5-4 x 10(9) yr ago). Both oxidized and reduced products would be expected. This is based on the inferred occurrence of hydrothermal activity during that time with the concomitant preservation of biochemically-derived organic matter. Both known biomarkers (i.e., as elucidated for early terrestrial samples and for primitive terrestrial microbiota) and novel, potentially unknown compounds should be characterized.

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.