P. Doumenq

Influence of n-alkanes and petroleum on fatty acid composition of a hydrocarbonoclastic bacterium: Marinobacter hydrocarbonoclasticus strain 617

This study concerns the effects of various long-chain n-alkanes, n-alkane mixtures and Arabian Light crude oil on the fatty acid (FA) composition of a sedimentary marine bacteria (Marinobacter hydrocarbonoclasticus strain 617), growing under aerobic conditions. The cultures with n-alkanes, as compared with soluble carbon sources, led to greater amounts of saturated and methyl branched FA (mainly belonging to a delta10 series). We observed the appearance or increase of saturated and unsaturated FA with the same carbon chain length (CCL) as the n-alkane carbon source (maximum for n-alkane CCL corresponding to the range of the de novo synthesized fatty acids). We also observed a strong control of the oddness/evenness of the CCL of the FA by the oddness/evenness of the n-alkane. A n-alkane utilization index, (saturated + branched)/monounsaturated fatty acids (SAFA + BFA/MUFA) enabled discriminating between soluble carbon sources and hydrocarbons.

Subfractionation, characterization and photooxidation of crude oil resins

Resins of five crude oils were obtained using SARA fractionation. The maltenic fraction of Blend Arabian Light, was further separated into six polar fractions. These fractions which are the constituents of the resins were analysed by FTIR spectroscopy. They appeared to be more oxidized, more aliphatic and less aromatic than asphaltenes. Photooxidation of resins showed that they are easily oxidizable and much more influenced by photooxidation than asphaltenes. The principal effect of photooxidation are: (i) increase of carbonyl group amounts and particularly formation of carboxylic groups, (ii) oxidation of sulfoxide in sulfone group, (iii) oxidation of alkyl chains and of aromatic rings (quinone structures).

In vitro photooxidation of crude oil maltenic fractions : Evolution of fossil biomarkers and polycyclic aromatic hydrocarbons

Abstract Photooxidation is an important transformation pathway for petroleum spilled in the marine environment. The maltenic fraction of ten crude oils was exposed to sunlight. Acidic and non-acidic photoproducts were analysed by FTIR spectroscopy and by GC/MS. A formation of carboxylic acids, straight-chain ketones and alcohols was observed. The GC/MS analyses of residual alkanes showed a preferential alteration of branched alkanes. The analyses of biomarkers such as drimanes, hopanes and steranes indicated that the GC/MS indices widely used in geochemistry, presented a great stability after photooxidation except for the Tm (Tm+Ts) ratio. Concerning the polycyclic aromatic hydrocarbons (PAHs), naphthalene and its derivatives were severely altered by photooxidation whereas, phenanthrene, dibenzothiophene and their derivatives were more recalcitrant. Methyl derivatives were more degraded than their parent molecules and in the case of methyl phenanthrenes, the 2-methyl phenanthrene had a great stability. The following sequence of increasing photodegradability of mono methylated phenanthrenes (MP) can be proposed: 2-MP

Occurrence of fatty acids linked to non-phospholipid compounds in the polar fraction of a marine sedimentary extract from Carteau cove, France

A surface sediment from Carteau cove, located at the western part of the Gulf of Fos (France), was collected and analysed to determine the lipid composition of its most polar fraction. Analyses by high performance liquid chromatography (HPLC) and thin-layer chromatography (TLC) of the polar fraction of the sediment extract revealed the presence of phospholipids (PL), with mainly phosphatidylglycerol (PG), phosphatidylethanolamine (PE) and lysophosphatidylethanolamine (LPE), but also the presence of non-phospholipid polar compounds (NPC). Phospholipids and non-phospholipid polar compounds (NPC) were isolated by preparative thin-layer chromatography and transmethylated. Phospholipid ester-linked fatty acids ranged from 12- to 20-carbon atoms and accounted for 34.8 m gg ˇ1 of dry sediment whereas fatty acids derived from non-phospholipid polar compounds ranged from 12- to 28-carbon atoms and accounted for 39.1 m gg ˇ1 of dry sediment. The occurrence of significant amounts of fatty acids derived from non-phospholipid polar compounds of a sediment polar fraction illustrates the importance of the preliminary analysis and purification of phospholipids to avoid an overestimation of the microbial biomass when determined with a current phospholipid ester-linked fatty acids (PLFA) analysis. # 2001 Elsevier Science Ltd. All rights reserved.

APPROCHE METHODOLOGIQUE DIRECTE ET CONTINUE DU PROCESSUS D'OXYDATION DES BITUMES PAR SPECTROSCOPIE INFRAROUGE A TRANSFORMEE DE FOURIER

Abstract (Direct continuous method for studying oxidation of bitumens by Fourier-transform infrared spectrometry). The method is based on the standard rolling thin-film oven test with oxidation in air at 163°C. A specially designed infrared cell is used. FTIR spectrometry provides spectral fingerprints which are characteristic for each bitumen.

Biodegradation of the (aliphatic + aromatic) fraction of Oural crude oil. Biomarker identification using GC/MS SIM and GC/MS/MS.

A simplified fraction of the Oural crude oil (aliphatic and aromatic hydrocarbons) was incubated in the presence of an hydrocarbonoclastic bacterial community isolated from a marine sediment highly contaminated by petroleum residue. The biodegradation has been carried out under aerobic conditions for 5 weeks and followed by FTIR, UV synchronous luminescence and GC/FID. Disappearance of the n-alkanes (2nd week), an important attack of the isoprenoïd compounds (5th week) and preferential alteration of monomethylated polyaromatics were observed. Concerning the biomarkers, the bicyclic alkanes and pentacyclic terpanes have been comparatively elucidated using GC/MS data. The identification of C(26) to C(29) steranes has required a most selective method, namely GC/MS/MS. Many molecular ratios based on GC/MS abundances were calculated, which showed good stability. Consequently, they can be used to determine the origin of a petroleum even one altered by biodegradation.

New approach to study of spilled crude oils using high resolution GC-MS (SIM) and metastable reaction monitoring GC-MS-MS

Polycyclic aromatic hydrocarbons (PAHs) and geochemical biomarkers are good environmental markers to study the origin and evolution of an oil spill. To have access to the greatest number of molecular ratios, no fractionation of oil into aliphatic and aromatic compounds is made. Three analytical MS approaches are tested to analyze markers in this total hydrocarbon fraction: classical quadrupole GC-MS, high resolution GC-MS (HR GC-MS) and metastable reaction monitoring GC-MS-MS (MRM GC-MS-MS). This analytical approach is used to follow the evolution of PAHs in petroleum polluted mangrove soils over 8 years by using molecular ratios between polycyclic aromatic hydrocarbons and tri- and tetracyclic terpanes.

Hydrocarbons and fatty acids in surficial sediments (French Mediterranean coastal zones)

A detailed study has been made of hydrocarbons and fatty acids in nine surficial Mediterranean sediments. The hydrocarbon concentrations are generally low. The nature and the distribution of the hydrocarbons found in these sediments indicate that they originate from several different sources (terrestrial, biogenic, pyrolytic) and petroleum inputs are usually not the main source of hydrocarbons. Fatty acid concentrations vary in the range 2-52 mg.kg-1 dry sediment. Fatty acid distributions, between C14 and C20 show the biogenic autochthonous inputs. Branched and cyclopropanic fatty acids reflect a bacterial origin. These distributions are markedly different in oxic and anoxic sediments.

The use of hopanes to track in situ variations in petroleum composition in surface sediments

Abstract Alterations in the composition of a Light Arabian crude oil has been studied in situ during 12 months in an artificially contaminated site. After 12 months of experimentation, C 17 Pr and C 18 Ph ratios could not be used, because the isoprenoids were no longer stable. In contrast, a high degree of stability of biomarkers, especially hopanes, was observed. These are very useful tools to assess alterations in other less stable classes of saturated compounds ( n -alkanes and isoprenoids) contained in petroleum. Marked degradation of both n -alkanes and isoprenoids (using 17α21β C 30 hopane as “internal standard”) has been evidenced. The use of biomarkers also made it possible to observe a burying process which occurred down to 6 cm deep after 12 months of experimentation.

Polychlorobiphenyls differentiation and identification by gas chromatography/fourier transform infrared spectroscopy

Reference infrared vapour phase spectra of 20 polychlorobiphenyls (PCBs) have been obtained by gas chromatography/Fourier transform infrared spectroscopy (GC/FTIR). These spectra are consistent with those of PCB obtained by diffuse reflectance IR spectroscopy (DRIFT) and with those of more simple molecular structures (iodochlorobenzenes, 1-bromodichlorobenzenes). The IR frequencies of the GC/FTIR spectra of PCB are assigned in terms of substitution patterns. This work shows that GC/FTIR can be a good approach for differentiation and identification of PCB in complex mixtures.