Aromatic Hydrocarbon Fractions Research Articles

Hydrocarbons in the Bay of Bengal and Central Indian Basin bottom sediments: indicators of geochemical processes in the lithosphere

A study on the bulk distributions and molecular structures of n-alkanes and polycyclic aromatic hydrocarbons (PAH) in organic matter of the sediments from the Bay of Bengal and the Eastern and Central Indian Basins was undertaken. The former two regions represent areas characterised by “normal” sedimentation while the third one mainly represents a region of “active tectonism”. Content of the hydrocarbons in the sediments of “normal” sedimentation ranges between 4.6 and 10.5 μg/g and aromatic hydrocarbons ranges between 0 and 0.38 μg/g. n-Alkanes in the sediments of the northern deep part of the Bay of Bengal consist mostly of long-chain structures (total C25–C33 up to 70%) with a high carbon preference index (CPI=3.01–3.43), indicating a large contribution of organic matter from terrigenous sources. The sediments from the Eastern Indian Basin have n-alkane distributions in which the long-chain components did not exceed 52.5% and the CPI was 1.7–1.90, indicating that the hydrocarbons are mostly derived from marine sources. Sharp increases of hydrocarbons are found in the vicinity of the tectonically active region of the Central Indian Basin, particularly in the sediments collected from the fracture zone. The total concentration of hydrocarbons increase to 170 μg/g and the aromatic hydrocarbons fraction to 156.3 μg/g. The proportion of short-chain n-alkanes increases up to 70%, CPI decreases to 0.76–1.12, and high concentrations of n-C16 (16–40%) occur, all of which are absent in the other samples. The molecular content of PAH includes the unsubstituted individual structures: biphenyl, fluorene, pyrene, perylene, benzo(ghi)perylene, and the groups of homologues of naphthalene, benzofluorene, phenanthrene and chrysene. The association of the PAH and composition of paraffin hydrocarbons in the surficial sediments of deformation zone indicate that these are the resultant products of hydrothermal processes. It is, therefore, suggested that the association and composition of the hydrocarbons in sediments can be utilised as a paleoceanographic parameter to decipher the history of tectonism of an area.

Bioavailability of Polycyclic Aromatic Hydrocarbons in the North Sea

Semipermeable membrane devices (SPMDs) and blue mussels (Mytilus edulis) were used to determine the bioavailable fraction of polycyclic aromatic hydrocarbons (PAHs) from oil field produced water in the North Sea. The SPMDs and mussels were deployed at 5, 10, and 50 m depth; 100 and 300 m downstream the discharge point; and at a reference site 16 km away. In both SPMDs and mussels, the concentration of PAHs increased significantly toward the discharge point, with the strongest contribution from the lower molecular weight compounds (naphthalene, phenanthrene, dibenzothiophene, and their C1−C3 alkyl homologues). The relative increase in PAH concentration from the reference site to the site at 100 m was higher for mussels than for the SPMDs. The SPMDs reflect the water-soluble fraction of the PAHs, which is probably the most important route of exposure for organisms at lower trophic levels and presumably also the fraction available for uptake by a respiratory route. Residues in the mussels represent both the water-soluble and particle-bound fraction and give information about bioavailability of the PAHs for organisms at higher trophic levels. The results of this study suggest that both techniques give important information about the bioavailability of PAHs to marine organisms.

Mutagenicity of various organic fractions of diesel exhaust particles.

Treated with various organic fractions of Diesel Exhaust Particles (DEP), the Ames test withSalmonella typhimurium strains TA98 and TA100, and the mice micronucleus test were employed to study the mutagenic activity in the bacterial reverse mutation system, with and without a mammalian S(9) activation component, and the clastogenic activity in mice polychromatic erythrocyte (PCE) stem cells. Extracted ultrasonically with dichloromethane then using the acid and base separated reaction and column chromatography, DEP were divided into five organic fractions. They are the organic acid fraction (Fl), the organic base fraction (F2), the aliphatic hydrocarbon fraction (F3), the aromatic hydrocarbon fraction (F4) and the polar fraction (F5). Results showed that an increase in the counted numbers of histidine revertants on theSalmonella TA100 and TA98 was observed with or without (S(9) mix), but these activities were more pronounced in the TA98 strains especially in the absence of the S(9) mix. These results suggest that the organic fractions of DEP contain mainly compounds with direct frame-shift mutaganicity. Positive results were also obtained from mice micronucleus assay. The frequency of mice bone marrow micronucleated polychromatic erythrocytes (PCE) was increased using this assay and it showed a definite dose-response relationship. The results suggest that various organic fractions could affect spindle fiber function or formation in mammalian cells. Compared with the results of different organic fraction, the effects of the F2, F4 and F5 were found to be stronger than those of other fractions. Based on the findings obtaind in the Ames and micronucleus tests, DEPs have genotoxic effects in both of the test systems.

Potential for intrinsic and enhanced crude oil biodegradation in Louisiana’s freshwater marshes

This study determined the intrinsic rates of biodegradation of Louisiana “sweet” crude oil (LSCO) in aPanicum hemitomon freshwater marsh using kinetic microcosm studies and verified the results in a large intact core study. In addition, the potential to enhance biodegradation using inorganic nutrient additions was determined. These freshwater marsh soils have high intrinsic rates of degradation (2.0%/day) for the measured alkane fraction (C11–C66) and even higher rates (6.8%/day) for the measured polycyclic aromatic hydrocarbon (PAH) fraction (naphthalene, methylated naphthalenes, phenanthrene, and methylated phenanthrenes). However, there were compound-specific effects with intrinsic rates of degradation highest for the smaller alkanes (C 15) were much lower (0.7–1.2%/day). Results from the intact core study indicate that these rates are similar to those experiencedin situ, with the exception of the PAH fraction, whose rate constants will be substantially lower than those determined in the kinetic study. Nitrogen (ammonium) was primarily the limiting nutrient and increased degradation rate constants (2–3 fold). Few differences were seen between different classes of alkanes after fertilization. Critical nitrogen loading rates (amount needed to produce significant degradation increases) were similar for both the microcosm and core study (2.2–8.8 mg NH4 +-N/g oil), while maximum rates of degradation were observed at higher loading rates (22–44 mg NH4 +-N/g oil). While crude oil degradation can be enhanced by fertilization, the benefits need to be weighed against the presence of high intrinsic biodegradation rates in these systems.

Potential for enhancement of biodegradation of crude oil in Louisiana salt marshes using nutrient amendments

Salt marsh ecosystems in Louisiana are at high risk of an oil contamination event while remediation of these systems is mainly limited to intrinsic bioremediation due to the physical sensitivity of salt marshes. This study investigated both the intrinsic and nutrient enhanced rates of crude oil degradation both in microcosm and core studies. In addition, limiting elements, loading rates and optimum nitrogen forms (NH 4 + or NO 3 - ) were determined. Salt marshes have relatively low intrinsic degradation rates (0–3.9% day-1) of the alkane component (C11-C44) but high rates (8–16% day-1) of degradation of the polycyclic aromatic hydrocarbon (PAH) fraction (naphthalene, C1, and C2-Naphthalene and Phenanthrene, C1, and C2-Phenanthrene). Additions of nitrogen statistically enhanced degradation of many alkanes and total PAHs while naturally present phosphorous was found to be sufficient. Nitrogen was found to be most effective if applied as NH 4 + in the range of 100-500-N mg kg-1 of soil producing a pore water range of 100-670-N mg L-1. Core studies indicate that similar trends are observed when applying fertilizers to intact portions of salt marsh.

Identification and Significance of Long Chain Fatty Acid Methyl Ester in the Surface Sediment of Taihu Lake

在太湖表层沉积物中检测出丰度较高的一系列长链脂肪酸甲酯化合物,采用标准图谱与质谱解析相结合的方法进行鉴定.长链脂肪酸甲酯化合物有类似正构烷烃的分布型式,碳数分布范围为C₁₄-C₃₄,主峰碳为C₁₆,具有明显的偶碳优势对太湖沉积物中长链脂肪酸甲酯化合物的来源、存在的地球化学环境等进行了讨论,初步认为长链脂肪酸甲酯化合物是反映湖泊沉积环境的重要有机标记化合物之一;The aromatic hydrocarbon fraction of the surface sediment in the west and east part of Taihu Lake was analyzed by GC-MS.As a result, a series of long chain falty acid methyl esters was first found. Distribution of the carbon number of fatty acid methyl esters in the samples was from C₁₄ to C₃₄ maximizing at C₁₆ with a strong even to odd carbon preference.Their mass spectrum characteristics are that base peaks were M/Z 74, 87 and characteristic ions were M/Z 143, 199, M⁺, M-43⁺.These ion existence was confirmed by fragmenting analyses of fatty acid methy esters.The origin of the long chain fatty acid methy esters in the sediment of Taihu Lake was also studied, which may be related to biochemical process. The result showed that the long chain fatly acid methyl esters was probably an important biological marker to study the acidity of the lake sediment.

Origins of heavy oils in the Erlian Basin, ne China

The Erlian Basin is located in the Central Asia-Mongolian fold belt between the Siberian and Sino-Korean Cratons. It is a Mesozoic continental rift basin composed of 52 individual fault-depressions. The main phase of rifting took place during the Early Cretaceous when a series of fluvial-lacustrine sediments were deposited. Each depression forms an independent sedimentary system and behaves as an independent petroleum system. Hydrocarbon source rocks are found in the upper Arshan and lower Tengger Formations. These are mainly type II source rocks and are mainly located in oil generation window at the present day. A series of oilfields and commercial oil flows have been found in the basin, highlighting its good petroleum potential. Many of these oils are heavy. Six oil samples from the Anan and ten from the Jirgalangtu Depressions have been subjected to routine geochemical analytical techniques in order to evaluate the origins. The methods used include gas chromatography of the saturated and aromatic hydrocarbon fractions, gas-chromatography-mass-spectrometry of the saturated hydrocarbon fraction and stable carbon isotope analyses. The trace metal elements of the biodegraded oils from the Jirgalangtu Depression were also analysed by atomic absorption spectroscopy. Two types of heavy oils : primary and biodegraded were identified on the basis of these data. The former includes both immature and mature heavy oils. A filtering-and-spill process was proposed to explain the origin of primary mature heavy oils (or tar-mat) in the Anan Depression. The biodegraded oils from the Jirgalangtu Depression were ranked and classified in terms of the degree of biodegradation, using a series of geochemical parameters based on the gas chromatographic concentrations and biomarker fingerprints of gas-chromatography-mass-spectrometry of the saturated hydrocarbon fraction. The relationship between oil saturation and porosity indicates that the heavy oils in the Jirgalangtu Depression were biodegraded after they accumulated.

The effect of maturity and biodegradation on the enantiomeric composition of sedimentary dihydro- ar-curcumene and related compounds

The effects of maturity and biodegradation on dihydro- ar-curcumene and isodihydro- ar-curcumene enantiomers have been assessed by applying chiral GC–MS techniques to aromatic hydrocarbon fractions obtained from crude oils and sedimentary rocks. Dihydro- ar-curcumene of natural origins undergoes rapid racemisation in the subsurface, yielding a racemic mixture before the onset of significant oil formation. 1,2-Alkyl shifts on the aromatic ring also begin at an early stage to yield isodihydro- ar-curcumene and continues with increasing maturity. Laboratory experiments using proton catalysts and clay (Lewis acid catalyst) show that the alkyl shift reaction is catalysed by proton and Lewis acids and racemisation is only catalysed by Lewis acids. A moderately biodegraded crude oil has been shown to be depleted in the R enantiomer of dihydro- ar-curcumene and an extensively degraded oil has dihydro- ar-curcumene depleted relative to isodihydro- ar-curcumene. These results indicate preferential metabolism of both enantiomers and positional isomers by degrading micro organisms.

Secular, episodic changes in stable carbon isotope composition of crude oils

Stable carbon isotopic compositions of C 15+ saturate and aromatic hydrocarbon fractions from 514 crude oils from known source rocks were examined for secular, episodic variations. The oils have been correlated by means of biomarker analyses and/or geological inferences to their respective source rocks and were further categorized into seven source rock types based on geochemical and petrologic indicators of depositional environments. Thus, these oil samples represent a wide range of source paleoenvironments from thirteen age divisions (Riphean to Neogene). The stable carbon isotopic compositions of both fractions become enriched in 13 C with decreasing geologic age. Three major, abrupt shifts toward 13 C enrichment occurred at the Precambrian–Cambrian/Ordovician, Triassic/Jurassic and Paleogene/Neogene boundaries. Analysis of smaller scale isotopic shifts reveals four distinct groups of oils, generally independent of organic facies and secondary alteration processes. Comparison of evolutionary changes in the biosphere to episodic changes in stable carbon isotopic compositions throughout the Phanerozoic indicates that isotopic shifts of crude oils may generally be related to the diversity of preserved phytoplankton.

Comparison of information-yield from different experimental designs used in algal toxicity testing of chemical mixtures

In controlled laboratory toxicity studies one often encounters situations where several variables might influence the biological response(s). Well-designed multivariate experiments allow for exploration of the effects of several variables simultaneously, and produce maximum information with maximum precision for a given experimental effort, as compared to the one-variable-at-a-time (univariate) approach. Thus, multivariate experimentation usually is the most cost-efficient but is rarely reported in the ecotoxicological literature. The aim of the present study has been to investigate the information-yield and predictive performance of models based on different statistical experimental designs for a given problem. Petroleum refinery wastewaters are complex mixtures. Previous work identified aromatic hydrocarbons and cyanide as the main contributors of a specific refinery effluent to in vivo chlorophyll a fluorescence inhibition of the marine diatom Skeletonema costatum. In the present article the effects of three variables (the aromatic hydrocarbon fraction [A], cyanide [C] and exposure time [T]) were investigated using four different duplicated experimental designs of various resource requirements (two-level factorial [FF(2)], central composite face-centred [CCF], Box-Behnken [BB] and three-level factorial [FF(3)] designs). Partial least squares (PLS) regression and analysis of variance (ANOVA) were applied in the data analysis. The prediction performances of the four models were evaluated by cross-validation and by predictions for new observations. The results show that the multivariate approach gathered all the information relevant to the stated problem in one mathematical model, and that considerable experimental effort can be saved by adopting a sequential modelling approach.

Solid-phase microextraction for determining the binding state of organic pollutants in contaminated water rich in humic organic matter

Solid-phase microextraction (SPME) in both conventional and headspace mode was used for determining the freely available and reversibly bound fraction of phenols and polycyclic aromatic hydrocarbons in contaminated water rich in dissolved polymeric organic matter (DOM). The SPME results obtained by using internal calibration with deuterated surrogates gave the total analyte concentration based on the identical partitioning behaviour of both, native pollutants and deuterated spikes, and agreed well with data from exhaustive LLE. Data obtained with direct and headspace SPME are very similar. Investigated matrices include both contaminated water and artificial DOM solutions. The DOM compounds were isolated from different aquatic and terrestrial sources and cover a wide range of hydrophobicity. A new approach based on progressive dilution of samples rich in DOM was developed for determining both the freely-dissolved fraction of an unknown analyte and its partition coefficients. Theoretical considerations provide strong evidence that the commonly used term `concentration' in SPME analysis should be replaced by the more appropriate term `activity' of the solute.

Performance studies of various cracking catalysts in the conversion of canola oil to fuels and chemicals in a fluidized‐bed reactor

AbstractStudies were conducted at atmospheric pressure at temperatures in the range of 400–500°C and fluidizing gas velocities in the range of 0.37–0.58 m/min (at standard temperature and pressure) to evaluate the performance of various cracking catalysts for canola oil conversion in a fluidized‐bed reactor. Results show that canola oil conversions were high (in the range of 78–98 wt%) and increased with an increase in both temperature and catalyst acid site density and with a decrease in fluidizing gas velocity. The product distribution mostly consisted of hydrocarbon gases in the C1–C5 range, a mixture of aromatic and aliphatic hydrocarbons in the organic liquid product (OLP) and coke. The yields of C4 hydrocarbons, aromatic hydrocarbons and C2–C4 olefins increased with both temperature and catalyst acid site density but decreased with an increase in fluidizing gas velocity. In contrast, the yields of aliphatic and C5 hydrocarbons followed trends completely opposite to those of C2–C4 olefins and aromatic hydrocarbons. A comparison of performance of the catalysts in a fluidized‐bed reactor with earlier work in a fixed‐bed reactor showed that selectivities for formation of both C5 and iso‐C4 hydrocarbons in a fluidized‐bed reactor were extremely high (maximum of 68.7 and 18 wt% of the gas product) as compared to maximum selectivities of 18 and 16 wt% of the gas product, respectively, in the fixed‐bed reactor. Also, selectivity for formation of gas products was higher for runs with the fluidized‐bed reactor than for those with the fixed‐bed reactor, whereas the selectivity for OLP was higher with the fixed‐bed reactor. Furthermore, both temperature and catalyst determined whether the fractions of aromatic hydrocarbons in the OLP were higher in the fluidized‐bed or fixed‐bed reactor.

98/01066 Fluidized bed combustion unit for oil shale: Hammad, M. et al. Energy Convers. Mgmt, 1998, 39, (3/4), 269–272

A study of the distributions of free and S-bound biomarkers and their δ13C values in the extract of a bulk sample of the Permian Kupferschiefer from the Lower Rhine Basin has been carried out to provide a more detailed characterization of the biological inputs. The distributions and isotopic compositions of selected components released from nickel boride desulphurization have been compared with those of components in the free fraction. The free biomarkers occur in greater abundance than their S-bound counterparts. The distribution and carbon isotopic composition of both free and bound components in the extract indicate a major cyanobacterial and algal input. Likewise, the free and bound aromatic hydrocarbons contain components which reveal an origin from the carotenoids of Chlorobiaceae (green sulphur bacteria), providing molecular evidence for the occurrence of photic zone anoxia in the water column. Most of the components in the complex mixture of mono-, di-, tri- and tetra-aromatics in the free aromatic hydrocarbon fraction result from cyclization and aromatization reactions.

Oil-source correlations as a tool in identifying the petroleum systems of the southern Taroom Trough, Australia

A geochemical study of crude oils and samples of various Permian, Triassic and Jurassic organic-rich rock units from the southern Taroom Trough was undertaken to test the prevailing Permian-source hypothesis for the petroleum reserves of the Bowen/Surat Basin. Seventy three core and cuttings samples were screened using organic petrography, total organic carbon analysis, Rock-Eval pyrolysis, and solvent extraction. Saturated and aromatic hydrocarbon fractions of selected source rocks, kerogen hydrous pyrolysates, and thirteen oils were then analysed by gas chromatography, gas chromatography-mass spectrometry and isotope ratio mass spectrometry, for the purpose of oil-to-source correlation. On the basis of their bulk carbon isotopic compositions and terpane, sterane and aromatic biomarker signatures, two oil families were identified. Those oils sourced by the Snake Creek Mudstone and reservoired in the Showgrounds Sandstone (both the Middle Triassic age) at Roswin North and Rednook are assigned to the “Snake Creek-Showgrounds” petroleum system. The remaining oils belong to the “Blackwater-Precipice” system. These originated in the Late Permian coal measures of the Blackwater Group but are produced from the Precipice Sandstone and other reservoir rocks of Permian to Jurassic age along the southeastern and southwestern margins of the trough.

Unusual polycyclic aromatic hydrocarbons in Lower Cretaceous Ostracode Zone sediments and related oils of the Western Canada sedimentary basin

Analyses of the aromatic hydrocarbon fractions of extracts of Lower Cretaceous Ostracode Zone sediments from the Western Canada sedimentary basin indicate the predominance of polycyclic hydroaromatic components. Most of these have not been previously reported in the literature, but are obviously diagenetically related to a new class of molecule whose natural distribution and biological significance remain to be determined. The components whose molecular structures have been confirmed, together with those for which tentative structural assignments are given, provide strong support for a pathway of progressive aromatisation of the presumed polyprenol precursors. These compounds appear to be specific markers for the Ostracode Zone sourced oils in the Lower Mannville Group reservoirs of the Provost area and may serve as excellent oil-source correlation parameters.

Liquid Chromatographic Separation of Sediment, Rock, and Coal Extracts and Crude Oil into Compound Classes

A method is described for the rapid fractionation of sediment, rock, and coal extracts and crude oils into compound classes. The method is based on combined polarity/affinity chromatography of soluble organic matter. Five heterocompound fractions are obtained in addition to the conventional saturated and aromatic hydrocarbon fractions. Model compound studies show that those fractions are chemically well-defined. The applicability to a variety of geological materials is demonstrated by analyzing a North Sea crude oil and solvent extracts of Posidonia shale, coal, and recent lake sediment samples. Generally reproducibilities and linearities are satisfactory. The total recoveries vary between 76% and 57%, depending on the sample type. The method is shown to be well-suited for the bulk compositional characterization of soluble organic matter. Separations can be performed on both the analytical and the semipreparative scales. Isolated fractions are amenable directly or after derivatization to qualitative and q...

Petroleum biodegradation in the Tertiary reservoirs of the North Sea

A suite of 17 oil samples from the Tertiary reservoirs (Palaeocene-Eocene) of the North Sea was subjected to routine geochemical analytical techniques in order to evaluate the degree of biodegradation. The methods included latroscan TLC-FID, gas chromatography of the saturated and aromatic hydrocarbon fractions, gas chromatography-mass spectrometry of the saturated hydrocarbon fraction and stable carbon and hydrogen isotope analyses. In addition, API gravities and weight percentages of asphaltene were also determined. Based on these data it was found that oils in the suite were derived from the Jurassic aged Kimmeridge Clay Formation originating from source rock horizons at similar maturity levels. The oils in the suite were taken from reservoirs with present day temperatures 49–114°C. Differences in the chemical composition of the oils (e.g. reduced relative amounts of saturated hydrocarbons, increased polar amounts and reduced relative concentrations of n-alkanes), were attributed to secondary alteration processes of which the most likely process to occur at temperatures less than 80°C and consistent with the observed chemical characteristics of the oils is biodegradation. The differences in chemical composition are thus attributed to different degrees of biodegradation. The oils were ranked and classified in terms of the degree of biodegradation using a range of restricting parameters based on the gas chromatographic concentrations of different alkane species. Based on these parameters, oils were divided into four classes. These classes are (a) non to slightly biodegraded; (b) mildly biodegraded; (c) moderately biodegraded; and (d) severely biodegraded. In cases where the degree of biodegradation was found to have reached levels where unambiguous identification of alkanes was not possible, unresolved complex mixture (UCM) parameters were utilised to assess the extent of biodegradation. The degree of biodegradation was subsequently compared to the type of reservoir sandstone facies from which oils in this study were taken. It was found that at similar temperatures, oils in the Balder Formation (Upper Late Palaeocene) were biodegraded to a higher degree compared to oils from either The Forties (Lower Late Palaeocene) or Sele (Middle Late Palaeocene) Formation. The higher degree of biodegradation in Balder reservoirs is attributed to relatively greater openness to meteoric water invasion in these reservoirs.

97/00141 Method and apparatus to improve secondary froth quality within oil and oil extraction process

A suite of 17 oil samples from the Tertiary reservoirs (Palaeocene-Eocene) of the North Sea was subjected to routine geochemical analytical techniques in order to evaluate the degree of biodegradation. The methods included latroscan TLC-FID, gas chromatography of the saturated and aromatic hydrocarbon fractions, gas chromatography-mass spectrometry of the saturated hydrocarbon fraction and stable carbon and hydrogen isotope analyses. In addition, API gravities and weight percentages of asphaltene were also determined.Based on these data it was found that oils in the suite were derived from the Jurassic aged Kimmeridge Clay Formation originating from source rock horizons at similar maturity levels.The oils in the suite were taken from reservoirs with present day temperatures 49–114°C. Differences in the chemical composition of the oils (e.g. reduced relative amounts of saturated hydrocarbons, increased polar amounts and reduced relative concentrations of n-alkanes), were attributed to secondary alteration processes of which the most likely process to occur at temperatures less than 80°C and consistent with the observed chemical characteristics of the oils is biodegradation. The differences in chemical composition are thus attributed to different degrees of biodegradation.The oils were ranked and classified in terms of the degree of biodegradation using a range of restricting parameters based on the gas chromatographic concentrations of different alkane species. Based on these parameters, oils were divided into four classes. These classes are (a) non to slightly biodegraded; (b) mildly biodegraded; (c) moderately biodegraded; and (d) severely biodegraded. In cases where the degree of biodegradation was found to have reached levels where unambiguous identification of alkanes was not possible, unresolved complex mixture (UCM) parameters were utilised to assess the extent of biodegradation. The degree of biodegradation was subsequently compared to the type of reservoir sandstone facies from which oils in this study were taken. It was found that at similar temperatures, oils in the Balder Formation (Upper Late Palaeocene) were biodegraded to a higher degree compared to oils from either The Forties (Lower Late Palaeocene) or Sele (Middle Late Palaeocene) Formation. The higher degree of biodegradation in Balder reservoirs is attributed to relatively greater openness to meteoric water invasion in these reservoirs.

Molecular indicators of palaeoenvironmental conditions in an immature Permian shale (Kupferschiefer, Lower Rhine Basin, north-west Germany) from free and S-bound lipids

A study of the distributions of free and S-bound biomarkers and their δ 13C values in the extract of a bulk sample of the Permian Kupferschiefer from the Lower Rhine Basin has been carried out to provide a more detailed characterization of the biological inputs. The distributions and isotopic compositions of selected components released from nickel boride desulphurization have been compared with those of components in the free fraction. The free biomarkers occur in greater abundance than their S-bound counterparts. The distribution and carbon isotopic composition of both free and bound components in the extract indicate a major cyanobacterial and algal input. Likewise, the free and bound aromatic hydrocarbons contain components which reveal an origin from the carotenoids of Chlorobiaceae (green sulphur bacteria), providing molecular evidence for the occurrence of photic zone anoxia in the water column. Most of the components in the complex mixture of mono-, di-, tri- and tetra-aromatics in the free aromatic hydrocarbon fraction result from cyclization and aromatization reactions.

Reduced biodegradability of desorption‐resistant fractions of polycyclic aromatic hydrocarbons in soil and aquifer solids

AbstractLess of the desorption‐resistant fractions of phenanthrene and naphthalene than freshly added phenanthrene and naphthalene was mineralized in columns of aquifer solids, loam, or muck. Slurrying columns of hydrocarbon‐amended aquifer solids, loam, or muck enhanced the rate and extent of mineralization of desorption‐resistant phenanthrene and naphthalene, but degradation was still less than in slurries amended with fresh compound. A substantial portion of the desorption‐resistant compound remained undegraded in the slurry. A surfactant and methanol increased the mineralization of resistant phenanthrene in slurries of loam. A mixed culture of microorganisms enriched on desorption‐resistant phenanthrene degraded twice as much of this fraction of compound as a pseudomonad. We suggest that predictions of the environmental fate of toxic chemicals require information on the biodegradability of the fraction of a compound that is resistant to desorption.