Oil Fingerprinting Research Articles

Oil biomarkers: main types, value and applications fields

Recent advances in modern chemistry provide environmental scientists with the ability to identify and track spilled oil residues in various environments. The compounds commonly used to identify the source of spilled oil are called biomarkers, they are universal in crude oil and petroleum products and are generally more stable to atmospheric environmental influences than most other oil constituents. The distribution of biomarker compounds is unique to each oil. Fingerprint indices calculated from oil fingerprints provide a stable and useful tool for determining the correspondence or non-correspondence of various oil residues present in some environmental samples. This paper highlights the main biomarkers of oil, their role in the study of oil and its deposits, and also shows the results of the authors’ own research.

Investigation of the quality of rapeseed oil derived from different varieties and growth periods based on GC-IMS technique

Rapeseed oil is consumed worldwide, and its quality is closely related to the raw rapeseed material. In this work, the quality and flavor differences of rapeseed oil from twelve varieties with two growth periods were studied. The results showed that different varieties responded differently to changes in growth periods, with the GXY1 variety having the greatest combined effect. Shortening the growth period may reduce the moisture and protein content and increase the oil content of rapeseed. It may also enhance the oleic acid content and decrease the linoleic acid content. A total of 62 aroma compounds were identified by gas chromatography-ion migration spectrometry (GC-IMS), with aldehydes being the main flavor compounds. The flavor fingerprint of rapeseed oil derived from different varieties was effectively constructed. Seven key aroma compounds with relative odor activity value (ROAV) > 1 were identified, which significantly influenced the flavor of rapeseed oil. This work may provide new insights for selecting favorable rapeseed varieties for industrial production of high-quality rapeseed oil.

Geochemical fingerprints of Dongpu Depression crude oils in Bohai Bay Basin, northern China: Insights from biomarkers and isotopic compositions of selected alkylnaphthalenes and alkylphenanthrenes

The Dongpu Depression is a rift lake in the Bohai Bay Basin of eastern China, where abundant oil and gas resources were discovered. Previous geochemical investigations of Dongpu Depression oils have revealed a notable lack of data regarding the isotopic compositions of individual polycyclic aromatic hydrocarbons (PAHs) from the discovered Cenozoic crude oils. Using gas chromatography-mass spectrometry (GC–MS) and gas chromatography-isotope ratio mass spectrometry (GC-IRMS), a novel approach combining molecular parameters and stable carbon isotope compositions of individual PAH was applied to study the depositional environment conditions, the different source inputs, the maturation stage and to identify the potential family of five crude oils selected from Dongpu Depression.A decrease of Ga/C30H together with low Pr/Ph ratios and changes in isotopic compositions indicate that the five Dongpu Depression oils were derived from OM deposited in an anoxic saline environment with a stratified water column where mixing of saline water and freshwater occurred. The low isoprenoid, tricyclic and tetracyclic terpane ratios in combination with the δ13C values of 1,6-DMN, 1,2,5-TMN, 1,3,6,7-TeMN, 9-MP and 1-MP attest that their sources have a mixed origin with high aquatic organism (planktonic) input and a lower land plant (C3 plant) contribution. The δ13C values of phenanthrene between −30.0 ‰ and −20.0 ‰ indicate that the studied Dongpu Depression oils belong to a single family generated from the peak to the late oil generation stage (Rc-TNR-2 between 0.85 and 1.15 %). A correlation with various basins indicates that oil samples featured by δ13C values of Phen between −30.0 ‰ and −20.0 ‰ correspond to crude oils derived from mixing of aquatic and high plant contributions with different degrees of mixtures, which have not yet reached their cracking stage (Rc < 2.0 %). Crude oils from the Carboniferous and Mesozoic-Cenozoic Tarim rocks, Australian petroleum systems, Termit Basin, Bongor Basin, Fushan Depression and the studied Dongpu Depression oils belong to that group of oils. Crude oils characterized by lighter phenanthrene isotopic compositions (δ13C values of Phen < −30.0 ‰) are mainly derived from marine/aquatic input and have already entered the cracking window (Rc > 2.0 %). This group of oils is represented in this study by the Cambrian-Ordovician Tarim Basin oil samples. The research shows the importance of the aromatic isotopic compositions in petroleum system characterization and could be used as a reference for a practical exploration campaign of petroleum.

Source differentiation of BTEX compounds in groundwater contaminated due to refinery activities

This study aims to identify sources of groundwater contamination in a refinery area using integrated compound-specific stable isotope analysis (CSIA), oil fingerprinting techniques, hydrogeological data, and distillation analysis. The investigations focused on determination of the origin of benzene, toluene, ethylbenzene, and xylenes (BTEX), and aliphatic hydrocarbons as well. Groundwater and floating oil samples were collected from extraction wells for analysis. Results indicate presence of active leaks in both the northern and southern zones. In the northern zone, toluene was found to primarily originate from oil products like aviation turbine kerosene (ATK or aviation fuel), kerosene, regular gasoline, and diesel fuel. Additionally, stable isotope ratios of carbon and hydrogen for ethylbenzene, o-xylene (ortho xylene) and p-xylene (para xylene) in zone A suggested the pollution originated from gasoline within the northern zone. The origin of super gasoline (with higher octane) identified in southern zone using δ13C and δ2H values of toluene in the floating oil and groundwater samples. Further, biodegradation of toluene likely occurred in southern zone according to δ13C and δ2H. The findings underscore the critical importance of integrating CSIA and fingerprinting techniques to effectively address the challenges of source identification and relying solely on each method independently is insufficient. Accordingly, comparing the GC-MS results of floating oil samples with ATK and jet fuel (JP4) standards can be effectively utilized for source differentiation. However, this method showed no practical application to distinguish different types of diesel or gasoline. The accuracy and reliability of source identification of BTEX compounds may significantly improve when hydrogeological data incorporates with stable isotopes analysis. Additionally, the results of this study will elevate the procedures for fuel-related contaminants source identification of the polluted groundwater that is crucial to develop effective remediation strategies.

Fingerprinting of monovarietal olive oils from Argentina and Uruguay via stable isotope, fatty acid profile, and chemometric analyses

Tracing methods of non-European EVOOs commercialized worldwide are becoming crucial for effective authenticity controls. Limited analytical studies of these oils are available on a global scale, similar to those of European EVOOs. We report for the first time the fatty acid concentrations, bulk-oil 2H/1H, 13C/12C, and 18O/16O ratios and fatty acid 13C/12C ratios of 43 authentic monovarietal EVOOs from different geographical regions in Argentina and Uruguay. The samples were obtained from a wide range of latitudes and altitudes along an E–W profile, from lowlands near the Atlantic Ocean to the pre-Andean highlands near the Pacific Ocean. Principal component scores were used to cluster EVOOs into three groups— central-western Argentina, central Argentina, and Uruguay—based on nine stable isotope ratios and the oleic-linoleic acid concentration ratio. The bulk 2H/1H and 18O/16O values and 13C/12C of palmitoleic and linoleic acids provide good tools for differentiating these oils via linear discriminant analysis.

Discrimination/Classification of Edible Vegetable Oils from Raman Spatially Solved Fingerprints Obtained on Portable Instrumentation.

Currently, the combination of fingerprinting methodology and environmentally friendly and economical analytical instrumentation is becoming increasingly relevant in the food sector. In this study, a highly versatile portable analyser based on Spatially Offset Raman Spectroscopy (SORS) obtained fingerprints of edible vegetable oils (sunflower and olive oils), and the capability of such fingerprints (obtained quickly, reliably and without any sample treatment) to discriminate/classify the analysed samples was evaluated. After data treatment, not only unsupervised pattern recognition techniques (as HCA and PCA), but also supervised pattern recognition techniques (such as SVM, kNN and SIMCA), showed that the main effect on discrimination/classification was associated with those regions of the Raman fingerprint related to free fatty acid content, especially oleic and linoleic acid. These facts allowed the discernment of the original raw material used in the oil's production. In all the models established, reliable qualimetric parameters were obtained.

Gas chromatography‐mass spectrophotometric profile of cold‐pressed Celastrus paniculatus seed oil and its high‐performance thin‐layer chromatographic analysis emphasizing squalene content

AbstractCelastrus paniculatus, a medicinal plant with diverse therapeutic activities, is known as ‘malkangani’ in the traditional medicine system of India, Ayurveda. It is well known for its memory‐enhancing potential. The reported work involves the gas chromatography‐mass spectrophotometric analysis of cold‐pressed seed oil of Celastrus paniculatus. It revealed the presence of components such as monosaturated fatty acids, polyunsaturated long‐chain fatty acids, and their derivatives. It also showed the presence of terpenes such as squalene, β amyrone, β amyrin acetate, and long‐chain hydrocarbons. Among all the constituents, squalene was found to be a major component. Hence, considering the potential pharmacological actions of squalene, a high‐performance thin‐layer chromatographic (HPTLC) method has been developed for its quantification and subsequently validated as per the International Conference of Harmonization guidelines. A HPTLC fingerprint of oil was obtained on pre‐coated silica gel 60 F254 aluminum sheets, using n‐hexane‐diethyl ether‐glacial acetic acid (7:3:0.05 v/v/v). A densitometric scan was performed at 470 nm after derivatization with vanillin sulphuric acid to quantify squalene. A well‐resolved squalene peak was obtained at a retardation factor of 0.85. It is a simple approach for the estimation of squalene in Celastrus paniculatus seed oil for quality control.

Herbal Emulgel Containing Azadirachta indica (Neem) and Nigella Sativa L. (Black Cumin) Oils in Wound Management: Preclinical Investigations

Abstract Context: In wound management, traditional use of plants has received attention by the scientific community, as traditional medicines are a valuable source of affordable, comprehensive medical care. Azadirachta indica A. Juss (Neem) and Nigella sativa Linn (Black cumin) are well known versatile medicinal plants with wide spectrum of biological activity. Methods: This study was undertaken to evaluate the wound healing activity of neem oil (NO) and black cumin oil (BCO) in rats. The oils were standardized using standard procedures. Gas chromatography mass spectrometry analysis and high performance thin layer chromatography fingerprinting of oils were carried out to identify major phytoconstituents present in the oils. The oils were suitably incorporated in carbopol based emulgel formulation, evaluated for physicochemical parameters and stability. Results: The wound healing potential assessed by the measurement of wound contraction and histopathology studies in excision and burn wound models, demonstrated comparable efficacy with standard nano crystalline silver gel (0.002% w/w). This may be attributed to the presence of phytoconstituents such as nimbidin and thymoquinone present in selected oils. Polyunsaturated fatty acid profile of BCO may be responsible for stimulating the release of vascular endothelial growth factor, which plays a significant role in accelerating wound healing process. Conclusion: Topical carbopol 934 base emulgel containing natural oils such as BCO and NO have been successfully prepared for wound management. However, further studies to establish the mechanistic aspects of wound healing needs to be undertaken.

Non-targeted Profiling of Sea Buckthorn Fruit Oil Fingerprints from 3 Regions and Study on Its Antioxidant Activity.

This study investigated the chemical and volatile characteristics of sea buckthorn fruits from three different regions in China. The chemical composition of the volatile oil was determined by using a non-targeted gas chromatography and mass spectrometry (GC/MS) method and the differences in chemical composition among the three producing areas were compared by heatmap providing a visual basis for researchers. A total of 93 compounds were identified, including 52 compounds from the Northeast China, 51 from the Xinjiang region, and 37 from Inner Mongolia region. Then, the in vitro antioxidant activity of sea buckthorn fruit oil was measured using DPPH, ABTS, and SOD inhibition tests, and the results showed that sea buckthorn fruit oil in northeast China was the strongest antioxidant, followed by Inner Mongolia and Xinjiang. The results of the CCK-8 experiment indicated that within the tested concentration, there is no cell cytotoxicity of the essential oil in human umbilical vein endothelial cells (HUVECs) cells. The results could supply reference to distinguish sea buckthorn fruit from different production areas and, meanwhile, clarify the activity and safety of sea buckthorn oil.

Quality Evaluation of Volatile Oil in Yanyangke Mixture (YM) Based on GC-MS Fingerprint, GC Multicomponent Quantitative Analysis and Chemical Pattern Recognition Analysis.

Yanyangke mixture (YM) is composed of 12 kinds of traditional Chinese medicine (TCM) used for the treatment of patients with cough, dry throat and other diseases caused by acute or chronic pharyngitis or patients with difficulty in expectoration. With the wide application of YM in clinical practice, its quality control has attracted huge attention. Based on the multi-component characteristics of Chinese herbal medicines, it is pertinent to establish a quality evaluation system. A new idea is to adopt gas chromatography-mass spectrometry (GC-MS) chemical composition identification, GC-MS fingerprint, and GC content determination as a potential quality control index of the volatile oil in YM. In this study, the volatile oil of YM was extracted by steam distillation, and the chemical components of the volatile oil were analyzed by GC-MS, and 43 chemical components were identified. The fingerprint of the volatile oil from YM was established and the similarity evaluation was performed. Combined with chemometric methods, such as cluster analysis, principal component analysis and partial least squares analysis, the chemical composition differences of the volatile oil from different batches of YM were compared and the symbolic components affecting the quality of the volatile oil from different batches of YM were excavated. Finally, three components were selected as the potential active component markers of YM and the GC content determination method of these three components was established. A rapid, reasonable, and effective quality evaluation and control method of YM volatile oil was established, which provided a reference for further development and research on YM, as well as a new idea for research on other TCM prescriptions.

The nature and magnitude of heterosis for the economic traits of vetiver{Chrysopogon zizanioides (L.) Roberty}

A total of 65 F1 vetiver hybrids were developed using the L × T design by mating 13 males with 5 females. The goal of this endeavor is to increase the possibility of developing high-yielding, quality essential oil varieties by utilizing heterosis and genetic variability. The heritability (%) was high for the traits CH4, CH7 to CH11 (81.90–99.69%). A positive and highly significant association exists between the features of CH2 and CH3. The trait CH8 showed the highest direct contributions to CH4, followed by CH-3, CH-5, CH4, and CH1. Heritability, correlations, and heterosis components all have an impact on the nature and degree of heterosis. It recommends that when selecting superior hybrids, breeders should take into account the genetic correlation between key traits. Based on average performance and heterosis for the root yield/plot, the top two crosses were determined to be L13 × T1 and L10 × T3. While hybrids L10 × T5, L2 × T3, and L4 × T5 showed high essential oil yield, four hybrids, L1 × T2, L3 × T3, L9 × T4, and L2 × T5, had the highest essential oil (%). A nor-sesquiterpene aldehyde (khusilal), two cedrene family chemicals (α-cedrenal and α-cedrenol), and one sesquiterpene alcohol, or khusol constitute the oil composition. The inclusion of just alcoholic and aldehydic components makes the oil fingerprint distinct. Further research was conducted on these hybrids to take advantage of heterosis and employ them in further hybridization programs to create superior genotypes.

Trace elements and organic geochemical fingerprinting of natural crude oils from the Monterey Formation, offshore Santa Maria Basin, California

Based on our recent analytical method development using microwave digestion and triple-quad ICP-MS, we have analyzed up to 57 elements for 20 natural crude oil samples from the offshore Santa Maria Basin of California, a prolific producing basin thought to be sourced dominantly from the Monterey Formation. Our goal is mainly to see if there were oil-oil correlations between wells (fractured reservoir mixing) or no correlation (locally sourced from an unconventional restricted depth reservoir or compartment), and which part (upper and/or lower) of the Monterey Formation acted as the primary source of oil. The results show distinct fingerprints based on V/Mo and Ni/Mo ratios derived from each of the wells where the oils were sampled during stem tests, indicating that they might be partially correlated with restricted intervals of the stratigraphy (or lithofacies). The V/Mo and Ni/Mo ratios of the oils also show that the lower Phosphatic-carbonate lithofacies of Monterey Formation may be a primary source of the oils. Vanadium and Ni contents, V/(Ni + V) ratios, and sulfur content of the oils indicate that the Monterey Formation was deposited under reducing marine conditions. The linear correlation between Mg and Ca contents and non-linear correlation between P and Ca contents in the oil samples may indicate that dolomite-rich rather than apatite-rich portions of Monterey Formation may be a critical source rock component. The similarity between REY distribution patterns of the oils and authigenic carbonate implies that carbonates might have been correlated with formation of the oils. Positive Eu anomalies in most oils reveal possible hydrothermal influences associated with magmatic and slab window effects as a consequence of the Farallon-Pacific Ridge subduction, higher heat flow, and later transtensional and transpressional deformation during deposition of Monterey Formation. The comparable REY distribution patterns for the oils and outcrop shales of Lions Head reveal potential oil-source correlations.

Application of Ion Mobility Spectrometry-Mass Spectrometry for Compositional Characterization and Fingerprinting of a Library of Diverse Crude Oil Samples.

Exposure characterization of crude oils, especially in time-sensitive circumstances such as spills and disasters, is a well-known analytical chemistry challenge. Gas chromatography-mass spectrometry is commonly used for "fingerprinting" and origin tracing in oil spills; however, this method is both time-consuming and lacks the resolving power to separate co-eluting compounds. Recent advances in methodologies to analyze petroleum substances using high-resolution analytical techniques have demonstrated both improved resolving power and higher throughput. One such method, ion mobility spectrometry-mass spectrometry (IMS-MS), is especially promising because it is both rapid and high-throughput, with the ability to discern among highly homologous hydrocarbon molecules. Previous applications of IMS-MS to crude oil analyses included a limited number of samples and did not provide detailed characterization of chemical constituents. We analyzed a diverse library of 195 crude oil samples using IMS-MS and applied a computational workflow to assign molecular formulas to individual features. The oils were from 12 groups based on geographical and geological origins: non-US (1 group), US onshore (3), and US Gulf of Mexico offshore (8). We hypothesized that information acquired through IMS-MS data would provide a more confident grouping and yield additional fingerprint information. Chemical composition data from IMS-MS was used for unsupervised hierarchical clustering, as well as machine learning-based supervised analysis to predict geographic and source rock categories for each sample; the latter also yielded several novel prospective biomarkers for fingerprinting of crude oils. We found that IMS-MS data have complementary advantages for fingerprinting and characterization of diverse crude oils and that proposed polycyclic aromatic hydrocarbon biomarkers can be used for rapid exposure characterization. Environ Toxicol Chem 2023;42:2336-2349. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Application of steady-state and time-resolved fluorescence spectroscopy in identification of cold-pressed vegetal oils

Monitoring the quality of food products is very important, due to the fact that substances potentially harmful to consumers may be formed during production and storage. In addition, vegetal oils are subject to falsification, which is based mainly on mixing and adding other, usually cheaper equivalents or providing false data on the composition and origin. In this way, the path from a very healthy product to a product that has a negative impact on the human body is very short. In this study fluorescence spectra and fluorescence decay kinetics of selected cold-pressed oils were characterized and the origin of the observed fluorescence bands was discussed. The obtained fluorescence characteristics were found to be the unique fingerprints of the individual oils and showed evident differences which arise from specific qualitative and quantitative compositions of the oils. The most apparent differences in the shape of fluorescence bands were observed in the emission spectrum at excitation wavelength 350 nm and in the excitation spectrum recorded at emission wavelength 500 nm. The obtained results show the utility of the applied steady-state and time –resolved fluorescence measurements in the identification of the tested vegetal oils.

HPTLC Analysis and Chemical Composition of Selected Melaleuca Essential Oils.

Tea tree oil (TTO) is a volatile essential oil obtained by distillation, mainly from the Australian native plant Melaleuca alternifolia (Maiden & Betche) Cheel (Myrtaceae). In this study, a comparative analysis of the chemical constituents of seven tea tree oils (M. alternifolia) and four other Melaleuca spp. oils (M. cajuputi, (MCa), two chemotypes of M. quinquenervia, (MNe and MNi), and M. ericifolia (MRo)) was carried out using gas chromatography-mass spectrometry (GC-MS) and high-performance thin-layer chromatography (HPTLC). Among the seven TTOs, terpinen-4-ol (37.66-44.28%), γ-terpinene (16.42-20.75%), α-terpinene (3.47-12.62%), α-terpineol (3.11-4.66%), and terpinolene (2.75-4.19%) were the most abundant compounds. On the other hand, the most abundant compounds of the other Melaleuca oils varied, such as 1,8-cineole (64.63%) in MCa oil, (E)-nerolidol (48.40%) and linalool (33.30%) in MNe oil, 1,8-cineole (52.20%) in MNi oil, and linalool (38.19%) and 1,8-cineole (27.57%) in MRo oil. HPTLC fingerprinting of Melaleuca oils enabled the discrimination of TTO oils from other Melaleuca spp. oils. Variation was observed in the profile of the Rf values among EOs. The present study shows that HPTLC is one of the best ways to identify and evaluate the quality control in authenticating TTOs, other Melaleuca EOs, or EOs from other species within the Myrtaceae.

Development of image similarity strategy based on targeted filtration for non-targeted HS-SPME/GC × GC fingerprints of volatile oils from Chinese patent medicines: A case of Chaihu Shugan Wan

To evaluate Chinese patent medicines more comprehensively, image similarity strategy based on targeted filtration was developed for non-targeted two-dimensional (2D) chromatographic fingerprints of volatile oil fraction in this paper. At first, volatiles and semi-volatiles were enriched from Chaihu Shugan Wan (CSW) by head space- solid phase micro-extraction (HS-SPME), and analyzed by comprehensive two-dimensional gas chromatography (HS-SPME-GC × GC). In succession, the inter-group and intra-group differences were distinguished by multi-component spectral correlative chromatography (MSCC). Facing the challenge of data complexity, some 50 contours were selected to indicate various medicinal materials through zone- specific ion filtration in 2D fingerprints. Among them, the known compounds were proven to be effective in “soothing liver-qi stagnation” through PubChem and other bioinformatic tools. Thirdly, Speeded Up Robust Features- Fast Library for Approximate Nearest Neighbors (SURF-FLANN) algorithm was utilized to estimate the pairwise similarities for the simplified fingerprints. In this procedure, the methodological examination was further made through the simulated images, including comparison with other algorithms, consideration for image complexity, and calculation of positives / negatives. At last, the similarities of six sample fingerprints were scored successfully. In summary, image similarity strategy based on zone- specific ion filtration can provide a viable solution for rapidly evaluating 2D fingerprints of extract fractions from Chinese patent medicines.

Mass spectrometry molecular fingerprinting of mineral and synthetic lubricant oils.

The molecular composition of lubricating oils has a strong impact on how automotive engines function, but the techniques used to monitor the quality parameters of these oils only inspect their gross physical-chemical properties such as viscosity, color, and bulk spectroscopy profiles; hence, bad-quality, adulterated, or counterfeit oils are hard to detect. Herein, we investigated the ability of direct infusion electrospray ionization mass spectrometry (ESI-MS) to provide simple, rapid but characteristic fingerprint profiles for such oils of the mineral and synthetic types. After a simple aqueous extraction, ESI-MS analyses, particularly in the positive ion mode, did indeed show characteristic molecular markers with unique profiles, which were confirmed and more clearly visualized by partial least squares-discriminant analysis (PLS-DA). Nuclear magnetic resonance and Fourier transform infrared-attenuated total reflection spectroscopy were also tested for the bulk samples but showed nearly identical spectra, thus failing to reveal their distinct molecular composition and to differentiate the oil samples. To simulate adulteration, mixtures of mineral and synthetic oils were also analyzed by ESI(+)-MS, and additions as low as 1% of mineral oil to synthetic oil could be detected. The technique therefore offers a simple and fast but powerful tool to monitor the molecular composition of lubricant oils, particularly vias their more polar constituents.

Variations in Polycyclic Aromatic Hydrocarbon Contamination Values in Subtidal Surface Sediment via Oil Fingerprinting after an Accidental Oil Spill: A Case Study of the Wu Yi San Oil Spill, Yeosu, Korea

This study determined the PAH contamination variations in the subtidal surface sediment with oil fingerprinting in the Wu Yi San oil spill in Yeosu, Korea, in January 2014. The ∑16 PAHs and ∑alkyl PAHs were investigated in surface sediment and seawater 1 month after the oil spill for 1 year at 3-month intervals in the accident (St. A-F) and adjacent areas (St. 1-20). The averaged ∑16 PAHs and ∑alkyl PAH concentration in the five samplings were 42.2–171.7 ng/g and 211.5–221.8 ng/g, respectively. Comparing the PAH levels in St.E and St.17 indicated a decreased tendency, from 357.9 to 31.1 ng/g dw. in ∑16 PAHs, and from 1900.9 to 211.5 ng/g dw. in ∑alkyl PAHs. The PAHs were not statically correlated between surface sediment and seawater (p &gt; 0.05), implying that the fate of PAHs was rapidly dispersed toward adjacent coasts and beaches. Pyrogenic origin was predominant in 16 PAHs, and petrogenic origin in alkylated PAHs. Notably, C2-D/C2-P and C3-D/C3-P ratios in the accident area during the first sampling were similar to accident oil, but the similarity was not shown in other samplings. Only the C2-naphthalene (St.A), C1-phenanthrene (St.A and St.B), and C2-phenanthrene (the entire accident area points) concentrations were higher than the ERL SQG.

Long-term patterns of hydrocarbon biodegradation and bacterial community composition in epipelagic and mesopelagic zones of an Arctic fjord

Oil spill attenuation in Arctic marine environments depends on oil-degrading bacteria. However, the seasonally harsh conditions in the Arctic such as nutrient limitations and sub-zero temperatures limit the activity even for bacteria capable of hydrocarbon metabolism at low temperatures. Here, we investigated whether the variance between epipelagic (seasonal temperature and inorganic nutrient variations) and mesopelagic zone (stable environmental conditions) could limit the growth of oil-degrading bacteria and lead to lower oil biodegradation rates in the epipelagic than in the mesopelagic zone. Therefore, we deployed absorbents coated with three oil types in a SW-Greenland fjord system at 10–20 m (epipelagic) and 615–650 m (mesopelagic) water depth for one year. During this period we monitored the development and succession of the bacterial biofilms colonizing the oil films by 16S rRNA gene amplicon quantification and sequencing, and the progression of oil biodegradation by gas chromatography – mass spectrometry oil fingerprinting analysis. The removal of hydrocarbons was significantly different, with several polycyclic aromatic hydrocarbons showing longer half-life times in the epipelagic than in the mesopelagic zone. Bacterial community composition and density (16S rRNA genes/ cm2) significantly differed between the two zones, with total bacteria reaching to log-fold higher densities (16S rRNA genes/cm2) in the mesopelagic than epipelagic oil-coated absorbents. Consequently, the environmental conditions in the epipelagic zone limited oil biodegradation performance by limiting bacterial growth.

Evaluation of Re–Os geochronology and Os isotope fingerprinting of Late Cretaceous terrestrial oils in Taranaki Basin, New Zealand

The rhenium-osmium (Re–Os) isotope system has been applied to several marine and lacustrine petroleum systems worldwide, showing good potential for dating crude oils and correlating them to their source rocks. Here we explore the applicability of the Re–Os geochronometer and Os isotope fingerprinting to terrestrial oils by comparing the Re and Os systematics of Late Cretaceous terrestrial oils from Taranaki Basin, New Zealand, and their correlated coaly source rocks. Comparison is also made with selected Late Cretaceous–Paleocene marine oils and source rocks with varying levels of terrestrial organic matter input.The asphaltene fractions of nine genetically related terrestrial oils from the Maui, Maari-Manaia and Tui Area fields in offshore Taranaki Basin contain low concentrations of Re (0.18–0.45 ppb) and 192Os (1.3–12.7 ppt) comparable to their correlated Late Cretaceous coaly source rocks (Rakopi and North Cape formations; Re 0.19–0.37 ppb, 192Os 5.3–9.6 ppt). The Re and 192Os concentrations in these terrestrial oils are generally one to two orders of magnitude lower than those in marine-sourced oils from the Kora Field in offshore Taranaki Basin and surface seeps in East Coast Basin.The 187Re/188Os and 187Os/188Os ratios of the terrestrial oils failed to yield a precise Re–Os isochron age. We attribute this to: (1) insufficient homogenisation of oils with widely variable initial 187Os/188Os (Osi) values inherited from thick, coaly source rock intervals (up to about 2700 m) within the Maui sub-basin and northern Kahurangi Trough kitchens; (2) insufficient spread of 187Re/188Os values (only 275 units); (3) insufficient time since oil expulsion (modelled to be from approximately 10 Ma to the present day) for the evolution of an isochron; and (4) possible effects of water washing of the oil columns. Although all of the studied oils are water-washed to varying degrees, there is no definitive evidence that water washing has disturbed the Re–Os systematics.The Osi values for the studied terrestrial oils inherited at the modelled time of oil expulsion (approximately 10 Ma) display a wide range (0.47–1.14) and do not provide a unique fingerprint of their Late Cretaceous coaly source rock formations. Osmium isotope compositions therefore appear to have limited potential for broad oil-source rock correlation within the predominantly coal-sourced petroleum systems of Taranaki Basin. The Osi values may, however, provide useful distinction of the terrestrial oils emanating from the Kahurangi Trough (Tui Area oils) from those of the Maui sub-basin (Maui and Maari-Manaia oils) based on the significantly more radiogenic values of the Tui Area oils (0.84–1.14 compared with 0.47–0.65 from Maui and Maari-Manaia oils). Overall, this study has provided useful insights into the potential application of the Re–Os isotope system to terrestrial, coal-sourced petroleum systems.