Hydrocarbon Constituents Research Articles

Bioreactor studies predict whole microbial population dynamics in oil sands tailings ponds

Microorganisms in oil sands fluid fine tailings (FFT) are critical to biogeochemical elemental cycling as well as to the degradation of residual hydrocarbon constituents and subsequent methane and CO2 production. Microbial activity enhances particulate matter sedimentation rates and the dewatering of FFT materials, allowing water to be recycled back into bitumen extraction. A bulk of this evidence comes from bioreactor studies and has implications for engineering and environmental management of the FFT ponds. Yet, it is largely uncertain whether such laboratory populations are representative of whole field scale microbial communities. By using population ecology tools, we compared whole microbial communities present in FFT bioreactors to reference populations existing in Syncrude's West In Pit (WIP) tailings pond. Bacteria were found to be persistent in a sulfidic zone in both the oxic and anoxic bioreactors at all occasions tested. In contrast to the WIP, archaea only became predominant in bioreactors after 300 days, at which point analysis of similarity (global R statistic p<0.5) revealed no significant dissimilarities between the populations present in either system. A whole community succession pattern from bacterial dominated prevalence to a new assemblage predominated by archaea was suggested. These results have implications for the stepwise development of microbial model systems for predictive management of field scale FFT basins.

Geochemical evidence for an Early Cambrian origin of the ‘Q’ oils and some condensates from north Oman

The Q family of oils from Oman was previously recognized as highly unusual and distinct from the more prevalent Huqf oil family by having an extraordinarily high C27/C29 sterane ratio and δ13C values near −30‰. A re-evaluation of the hydrocarbon constituents of the Q oils using GC–MS–MS analyses resulted in identification of other useful geochemical discriminators that include gammacerane/hopane ratios between 0.5 and 0.9, C24T/C23T⩾0.7 combined with C22T/C21T cheilanthane ratios <0.4. A relatively simple branched alkane, 17-methylpentatriacontane, identified on the basis of its mass spectrum is especially characteristic. A suite of C19, C20 and C26 norsteranes, characterized by a dominant 203Da fragment in their mass spectra, were also present with an abundance pattern that distinguished the Q oils from other south Oman oil families and their source rocks. These features enabled us to establish a Q-source rock as the origin of a suite of highly mature condensates from north Oman despite them having exceptionally low concentrations of conventional biomarkers.Although we were unable to identify a source facies within the sediments of the South Oman Salt Basin that convincingly correlated with the hydrocarbons of the Q oils, the geochemistry of Q oils provided valuable clues about their origin. Sterane and terpane patterns indicated that the Q source rock is most likely a marine shale deposited under intermittently anoxic and hypersaline conditions. The absence of a carbon isotopic ordering anomaly for normal alkanes and isoprenoids points to a Cambrian age for the Q oils. Moreover, trends in the patterns of norsteranes in south Oman carbonate stringer oils suggest the Q oil source originates from one of the upper units of the Ara carbonate and evaporite sequence. More specifically, our results point to a siliciclastic source rock lying stratigraphically above the A6 carbonates from the Dhahaban Formation. The high relative abundances of 24-isopropylcholestanes in Q oils likely originate from demosponges and we hypothesize that the 17-methylpentatriacontane, which is so abundant in Q oils, is a biomarker for early arthropods that inhabited the salt basins of Oman at the very beginning of the Cambrian Period.

Alkane Degradative Potentials of Bacteria Isolated From the Deep Atlantic Ocean of the Gulf of Guinea

The efficiency of bacterial strains isolated from Nigeria Deep Atlantic Ocean water and sediment (2450 m – 2774 m depths) to biodegrade total petroleum hydrocarbons (TPH, n-alkanes) constituents of 1% crude oil was compared with that of similar isolate from oily wastewater reservoir in Imo State, Nigeria. Standardized bacterial strains (OD546 1.0) with similar morphological and biochemical characteristics from surface seawater (HBW12a), bottom seawater (HBW12b), superficial sediment (HBS12) and oily wastewater reservoir (HMWP) were selected and their TPH biodegradation efficiency in 30 days was quantified by gas chromatographic analysis (GC-FID). TPH fractions (n-C8–n-C40) of Bonny light crude oil was degraded significantly (P≤0.05) by all the four isolates. HMWP, HBW12b, HBS12 and HBW12a degraded 85.7%, 80.8%, 79.1% and 78.6% of TPH respectively. Although bacterial isolates from oily wastewater reservoir (HMWP) possessed highest degradative capabilities, isolates from seawater surface (HBW12a) and seawater bottom (HBW12b) as well as sediment (HBS12) also exhibited crude oil degradative potential. The four isolates have been tentatively identified as Pseudomonas. The gas chromatograms showed a distribution from n-C11 to n-C36 alkanes with the fractions of n-C15, n-C17 and n-C19 showing relatively high concentrations at the onset of experiment followed by a significant degradation in 30 days by all the isolates. The n-C17/pristane peak ratios of 0.43, 0.47, 0.47 and 0.48 for HMWP, HBW12a, HBW12b and HBS12 respectively in day 30 also affirmed TPH biodegradation by all the isolates. Indigenous bacteria from deep Atlantic Ocean water column and sediment thus possess capabilities for biotechnological applications in deep water bioremediation.

Generation of free radicals in haemocytes of mussels after exposure to low molecular weight PAH components: Immune activation, oxidative and genotoxic effects

Polycyclic aromatic hydrocarbons (PAHs) constituents, such as phenanthrene (PH) and anthracene (AN), are considered toxic for marine organisms, including bivalve mollusks. The present study showed that the perturbation of health status in mussels, as well as their inability to survive in air (stress on stress response), following exposure to either PH or AN (at a final concentration of 0.1mg/L respectively), and a mixture of them (ration 1:1, at a final concentration of 0.2mg/L) for 7days, is probably related with alterations occurred in their haemocytes. According to the present study, PH and AN, either alone or in a mixture, could induce elevated levels of superoxide anions (•O2−) within haemocytes of mussels, thus leading to immune susceptibility as indicated by the increased levels of cell death and the elevated levels of lysosomal membrane acid phosphatase (AcP) activity, probably occurred via its overproduction or its release into the cytosol after lysosomal membrane destabilisation. PAH-mediated oxidative and genotoxic effects, indicated by the increased levels of both lipid peroxidation (MDA content) and nuclear abnormalities (MN test) could be related with haemocytes' inability to overcome free radical generation, thus leading to attenuation of general health status, before other disturbances, such as death, occur.

Evaluation of membrane bioreactor for hypersaline oily wastewater treatment

Produced water is a significant waste stream generated in association with oil and gas production. It contains high concentrations of hydrocarbon constituents and different salts. In this study, a membrane sequencing batch reactor (MSBR) was used to treat synthetic and real produced water. The MSBR was evaluated in terms of biodegradation of hydrocarbons in the synthetic produced water with various organic loading rates (OLR) (0.281, 0.563, 1.124, 2.248, and 3.372 kg COD/(m 3 day)), cycle time (12, 24, and 48 h), and membrane performance. The effects of salt concentrations at different total dissolved solids (TDS) (35,000, 50,000, 100,000, 150,000, 200,000, and 250,000 mg/L) on biological treatment of the pollutants in the synthetic and real wastewater were studied. At an OLR of 1.124 kg COD/(m 3 day), an HRT of 48 h and TDS of 35,000 mg/L, removal efficiencies of 97.5%, 97.2%, and 98.9% of COD, total organic carbon (TOC), and oil and grease (O&G), respectively were achieved. For the real produced water, removal rates of 86.2%, 90.8%, and 90% were obtained for the same conditions. However, with increasing salt content, the COD-removal efficiencies of the synthetic and real produced water were reduced to 90.4% and 17.7%, respectively at the highest TDS.

Correlation Between Speciated Hydrocarbon Emissions and Flame Ionization Detector Response for Gasoline/Alcohol Blends

The U.S. renewable fuel standard has made it a requirement to increase the production of ethanol and advanced biofuels to 36 billion by 2022. Ethanol will be capped at 15 billion, which leaves 21 billion to come from other sources such as butanol. Butanol has a higher energy density and lower affinity for water than ethanol. Moreover, alcohol fueled engines in general have been shown to positively affect engine-out emissions of oxides of nitrogen and carbon monoxide compared with their gasoline fueled counterparts. In light of these developments, the variety and blend levels of oxygenated constituents is likely to increase in the foreseeable future. The effect on engine-out emissions for total hydrocarbons is less clear due to the relative insensitivity of the flame ionization detector (FID) toward alcohols and aldehydes. It is well documented that hydrocarbon (HC) measurement using a conventional FID in the presence of oxygenates in the engine exhaust stream can lead to a misinterpretation of HC emissions trends for alcohol fuel blends. Characterization of the exhaust stream for all expected hydrocarbon constituents is required to accurately determine the actual concentration of unburned fuel components in the exhaust. In addition to a conventional exhaust emissions bench, this characterization requires supplementary instrumentation capable of hydrocarbon speciation and response factor independent quantification. Although required for certification testing, this sort of instrumentation is not yet widely available in engine development facilities. Therefore, an attempt is made to empirically determine FID correction factors for oxygenate fuels. Exhaust emissions of an engine fueled with several blends of gasoline and ethanol, n-butanol and iso-Butanol were characterized using both a conventional FID and a Fourier transform infrared. Based on these results, a response factor predicting the actual hydrocarbon emissions based solely on FID results as a function of alcohol type and content is presented. Finally, the correlation derived from data presented in this study is compared with equations and results found in the literature.

Hydrocarbon prospects across Narmada–Tapti rift in Deccan trap, central India: Inferences from integrated interpretation of magnetotelluric and geochemical prospecting studies

As the Mesozoic sediments contribute most of the oil and gas reserves of the world, we present an integrated interpretation approach using magnetotellurics (MT) and surface geochemical prospecting studies to demarcate hydrocarbon prospective Gondwana (Mesozoic) formations underneath the Deccan flood basalts of Late Cretaceous age across Narmada–Tapti rift (between Bhusawal and Barwah) in Central India. The MT interpretation shows deep (∼5 km) basement structure between southern and central part of the MT profile however, it gradually becomes shallower to either ends of the profile with a predominant basement depth reduction in the northern end compared to the southern end. The geophysical results suggest thick (2–3.5 km) Mesozoic sediments in the area characterized by deep basement structure. The geochemical analysis of the near surface soil samples indicate higher concentrations of light gaseous hydrocarbons constituents over the area marked with thick sub-basalt Mesozoic formations. Analyses of the geochemical data imply that these hydrocarbons are genetically related, generated from a thermogenic source and these samples fall in the oil-producing zone. The temperature–depth estimations in the region supports favorable temperature conditions (80–120 °C) for oil generation at basement depths.

Candida keroseneae sp. nov., a novel contaminant of aviation kerosene

To characterize and identify a novel contaminant of aviation fuel. Micro-organisms (yeasts and bacteria) were isolated from samples of aviation fuel. A yeast that proved to have been unrecorded previously was isolated from more than one fuel sample. This novel yeast proved to be a new species of Candida and is described here. Ribosomal RNA gene sequence analyses of internal transcribed spacer (ITS) regions (including 5·8S subunit) plus the 26S D1/D2 domains showed the strains to cluster within the Candida membranifaciens clade nearest to, but distinct from, Candida tumulicola. Phenotypic tests were identical for both isolates. Physiological and biochemical tests supported their position as a separate taxon. The yeast was assessed for its effect on the main constituent hydrocarbons of aviation fuel. Two strains (IMI 395605(T) and IMI 395606) belonging to the novel yeast species, Candida keroseneae, were isolated from samples of aircraft fuel (kerosene), characterized and described herein with reference to their potential as contaminants of aviation fuel. As a result of isolating a novel yeast from aviation fuel, the implications for microbial contamination of such fuel should be considered more widely than previously thought.

Investigations on surrogate fuels for high-octane oxygenated gasolines

Gasoline is a complex mixture that possesses a quasi-continuous spectrum of hydrocarbon constituents. Surrogate fuels that decrease the chemical and/or physical complexity of gasoline are used to enhance the understanding of fundamental processes involved in internal combustion engines (ICEs). Computational tools are largely used in ICE development and in performance optimization; however, it is not possible to model full gasoline in kinetic studies because the interactions among the chemical constituents are not fully understood and the kinetics of all gasoline components are not known. Modeling full gasoline with computer simulations is also cost prohibitive. Thus, surrogate mixtures are studied to produce improved models that represent fuel combustion in practical devices such as homogeneous charge compression ignition (HCCI) and spark ignition (SI) engines. Simplified mixtures that represent gasoline performance in commercial engines can be used in investigations on the behavior of fuel components, as well as in fuel development studies. In this study, experimental design was used to investigate surrogate fuels. To this end, SI engine dynamometer tests were conducted, and the performance of a high-octane, oxygenated gasoline was reproduced. This study revealed that mixtures of iso-octane, toluene, n-heptane and ethanol could be used as surrogate fuels for oxygenated gasolines. These mixtures can be used to investigate the effect of individual components on fuel properties and commercial engines performance.

Microbiological impacts of produce water discharges in nearshore shallow marine waters near Chevrons Escravos tank farm, Nigeria

Microbiological and Physicochemical survey was undertaken in produced water and its receiving environment with the aim of verifying the likely impacts of produced water constituents on the immediate receiving marine near shore shallow environment. The sampling was carried out in two seasons, late wet season and late dry season. The results obtained indicate that the chemical constituents of the discharged produce water are capable of sustaining microbial growth and proliferation. Produce water from Escravos tank farm had relatively moderate concentrations of hydrocarbon utilizing microorganisms and sulphate reducing bacteria and the concentration of these organisms were much higher at the point of discharge of the produced water. Physicochemical analysis showed that Produce water had lower salinity and sulphate levels than the receiving marine water but the reverse was the case with the BOD, COD and Hydrocarbon constituents. The two seasons under investigation showed similar results. From the analytical data, it can be advanced that the impacts of produced water microbial flora on the receiving environment is limited to the vicinity of the discharge point of about 100 m in diameter and also to some extent up to a distance of 500 m upstream along the direction of flow of produced water discharges. It is expected that while the hydrocarbon degrading microorganisms plays a beneficial role of degrading and detoxifying abundant produced water hydrocarbons in the sediment and the surface water, Sulphate reducing bacteria might at the same time be playing a detrimental role of oxidizing certain organic compounds or hydrogen and reducing sulphate and other reduced sulphur compounds in the marine water and sediment to hydrogen sulphide which can be very toxic to bacteria, aquatic animals and man. Key words: Produced water, sulphate reducing bacteria, hydrocarbon utilizing bacteria.

Khasib and Tannuma oil sources, East Baghdad oil field, Iraq

This work presents new insights of the generation, quality and migration pathways of the hydrocarbons in the East Baghdad Oil Field. The Khasib and Tannuma formations in East Baghdad are considered as oil reservoirs according to their high porosity (15–23%) and permeability (20–45 mD) in carbonate rocks. The hydrocarbons are trapped by structural anticline closure trending NW-SE. Gas chromatography analysis on these oil reservoirshave shown biomarkers of abundant ranges of n-alkanes of less than C22 (C17–C21) with C19 and C18 peaks. This suggests mainly liquid oil constituents of paraffinic hydrocarbons from marine algal source of restricted palaeoenvironments in the reservoir. The low non aromatic C15 + peaks are indicative for slight degradation and water washing. Oil biomarkers of Pr./Ph. = 0.85, C31/C30 < 1.0, location in triangle of C27–C29 sterane, C28/C29 of 0.6 sterane, Oleanane of 0.01 and CPI = 1.0, indicate an anoxic marine environment with carbonate deposits of Upper Jurassic to Early Cretaceous age. Four Miospores, seven Dinoflagellates and one Tasmanite species confirm affinity to the upper most Jurassic to Lower Cretaceous Chia Gara and Ratawi Formations.The recorded palynomorphs from the Khasib and Tannuma Formations are of light brown color of TAI = 2.8–3.0 and comparable to the mature palynomorphs that belong to the Chia Gara and the Lower part of Ratawi Formations. The Chia Gara Formation generated oil during Upper Cretaceous to Early Palaeogene and accumulated in structural traps of Cretaceous age, such as the Khasib and Tannuma reservoirs. The Chia Gara Formation generated and expelled high quantities of oil hydrocarbons according to their TOC wt% of 0.5–8.5 with S2 = 2.5–18.5 mg Hc/g Rock, high hydrogen index of the range 150–450 mg Hc/g Rock, good petroleum potential of 4.5–23.5 mg Hc/g Rock, mature (TAI = 2.8–3.0 and T max = 428–443C), kerogen type II and palynofacies parameters of up to 100% AOM (Amorphous Organic Matters). This includes algae deposits in a dysoxic–anoxic to suboxic–anoxic environment. Alternative plays are discussed according to the migration pathways.

Application of membrane-coupled sequencing batch reactor for oilfield produced water recycle and beneficial re-use

Oil and gas field wastewater or produced water is a significant waste stream in the oil and gas industries. In this study, the performance of a membrane sequencing batch reactor (MSBR) and membrane sequencing batch reactor/reverse osmosis (MSBR/RO) process treating produced wastewater were investigated and compared. The MSBR was operated in different hydraulic residence time (HRT) of 8, 20 and 44 h. Operation results showed that for a HRT of 20 h, the combined process effluent chemical oxygen demand (COD), total organic carbon (TOC) and oil and grease (O&G) removal efficiencies were 90.9%, 92% and 91.5%, respectively. The MSBR effluent concentration levels met the required standard for oil well re-injection. The RO treatment reduced the salt and organic contents to acceptable levels for irrigation and different industrial re-use. Foulant biopsy demonstrated that the fouling on the membrane surface was mainly due to inorganic (salts) and organic (microorganisms and their products, hydrocarbon constituents) matters.

Cretaceous petroleum system of the Khasib and Tannuma oil reservoir, East Baghdad oil field, Iraq

Gas chromatography, palynomorph constituents, and maturation are analyzed for oil samples of the Campanian Khasib and Tannuma Formations in the wells of East Baghdad oil field for biomarker studies, while palynomorph constituents and their maturation, Rock Eval pyrolysis, total organic carbon (TOC) analysis are carried on for the Upper Jurassic and the Cretaceous Formations of core samples from the same wells for dating and evaluation of the source rocks. The gas chromatography of these oils have shown biomarkers of abundant ranges of n-alkanes of less than C22(C17–C21) with C19 and C18 peaks to suggest mainly liquid oil constituents of paraffinic hydrocarbons from marine algal source of restricted palaeoenvironments in the reservoir as well as low nonaromatic \( {\hbox{C}}_{15}^{+} \) peaks to indicate their slight degradation and water washing. Oil biomarkers of \( \Pr ./{\hbox{Ph}}{.} = {0}{.85,}{{\hbox{C}}_{31}}/{{\hbox{C}}_{30}} < 1.0 \), location is in the triangle of C27–C29 sterane, C28/C29 of 0.6 sterane, oleanane of 0.01, and CPI = 1.0, could indicate anoxic marine environment with carbonate deposition of Upper Jurassic–Early Cretaceous source. The recorded palynomorph constituents in this oil and associated water are four miospore, seven dinoflagellates, and one Tasmanite species that could confirm affinity to the Upper most Jurassic–Lower Cretaceous Chia Gara and Ratawi Formations. The recorded palynomorphs from the reservoir oil (Khasib and Tannuma Formations) are of light brown color of \( {\hbox{TAI}} = 2.8 - 3.0 \) and comparable to the mature palynomorphs that belong to Chia Gara and Lower part of Ratawi Formations. Chia Gara Formation had generated and expelled high quantity of oil hydrocarbons according their TOC weight percent of 0.5–8.5 with \({S_2} = 2.5 - 18.5\,{\hbox{mg}}\,{\hbox{Hc/g}}\;{\hbox{rock}} \), high hydrogen index of the range 150–450 mg Hc/g Rock, good petroleum potential of 4.5–23.5 mg Hc/g rock, mature (\( {\hbox{TAI}} = 2.8 - 3.0 \) and \( {\hbox{T}}\max = 428 - 443{\hbox{C}} \)), kerogen type II, and palynofacies parameters of up to 100 amorphous organic matters with algae deposited in dysoxic–anoxic to suboxic–anoxic basin, while the palynomorphs of the rocks of Khasib Formation are of amber yellow color of TAI = 2.0 with low TOC and hence not generated hydrocarbons. But, this last formation could be considered as oil reservoir only according their high porosity (15–23%) and permeability (20–45 mD) carbonate rocks with structural anticline closure trending NW-SE. That oil have generated and expelled during two phases; the first is during Early Palaeogene that accumulated in traps of the Cretaceous structural deformation, while the second is during Late Neogene’s.

Phase behavior, microstructure transition, and antiradical activity of sucrose laurate/propylene glycol/the essential oil of Melaleuca alternifolia/water microemulsions

Nonionic sucrose ester microemulsions composed of sucrose laurate (SL), propylene glycol (PG) and water were prepared with the essential oil of Melaleuca alternifolia, commonly known as tea tree oil (TTO), as oil phase to investigate the phase behavior, microstructure, and antiradical activity. The pseudo-ternary phase diagrams were constructed to elucidate the phase behavior of the microemulsion formations at different weight ratios of surfactant and cosurfactant ( S m = SL/PG) of 1:1, 2:1, and 3:1. The extension of the microemulsion zone was found to be strongly dependent on the S m ratios. The single phase microemulsion domain, especially o/w microemulsion region increased when S m ratio is increased from 1:1 to 3:1 and no liquid crystalline structure was observed for all formulations studied. Microstructural aspects were studied by electrical conductivity and pulsed gradient spin echo (PGSE) NMR measurements along water titration line L28 ( R o = 2:8). The results from these combined techniques were in good agreement in regard to the microstructure transition points. The microstructural inversion of w/o to bicontinuous microemulsions occurred at ∼30 wt.% water while the transition from bicontinuous to o/w structure occurred at ∼55 wt.% water. The physical stability on storage temperature and time was examined by dynamic light scattering after the centrifuge test and freeze–thaw cycles. The droplet size was kept almost the same without any phase separation, providing less temperature-sensitivity up to 70 °C and good stability for 3 months at room temperature. The chemical profile and radical scavenging activity of TTO in o/w microemulsions was evaluated by means of gas chromatography–mass spectroscopy (GC–MS) and 2,2′-diphenyl-1-picrylhydrazyl free radical (DPPH ) scavenging method, respectively. The major abundant constituents of crude TTO, monoterpene alcohols (terpinen-4-ol (41.65%), α-terpineol (3.18%)) and hydrocarbons (γ-terpinene (22.95%), α-terpinene (10.16%)) were identified and the composition percentage of each constituent was calculated form the GC peak areas by normalization method. The DPPH scavenging activity of TTO microemulsion was lower than pure TTO because the SL surfactant may obstruct the interaction between the TTO and DPPH , reducing the number of effective collisions.

Hydrocarbon biodegradation and soil microbial community response to repeated oil exposure

Bioremediation strategies continue to be developed to mitigate the environmental impact of petroleum hydrocarbon contamination. This study investigated the ability of soil microbiota, adapted by prior exposure, to biodegrade petroleum. Soils from Barrow Is. (W. Australia), a class A nature reserve and home to Australia’s largest onshore oil field, were exposed to Barrow production oil (50 ml/kg soil) and incubated (25 °C) for successive phases of 61 and 100 days. Controls in which oil was not added at Phase I or II were concurrently studied and all treatments were amended with the same levels of additional nutrient and water to promote microbial activity. Prior exposure resulted in accelerated biodegradation of most, but not all, hydrocarbon constituents in the production oil. Molecular biodegradation parameters measured using gas chromatography–mass spectrometry (GC–MS) showed that several aromatic constituents were degraded more slowly with increased oil history. The unique structural response of the soil microbial community was reflected by the response of different phospholipid fatty acid (PLFA) sub-classes (e.g. branched saturated fatty acids of odd or even carbon number) measured using a ratio termed Barrow PLFA ratio (B-PLFAr). The corresponding values of a previously proposed hydrocarbon degrading alteration index showed a negative correlation with hydrocarbon exposure, highlighting the site specificity of PLFA-based ratios and microbial community dynamics. B-PLFAr values increased with each Phase I and II addition of production oil. The different hydrocarbon biodegradation rates and responses of PLFA subclasses to the Barrow production oil probably relate to the relative bioavailability of production oil hydrocarbons. These different effects suggest preferred structural and functional microbial responses to anticipated contaminants may potentially be engineered by controlled pre-exposure to the same or closely related substrates. The bioremediation of soils freshly contaminated with petroleum could benefit from the addition of exhaustively bioremediated soils rich in biota primed for the impacting hydrocarbons.

Characterization of permineralized kerogen from an Eocene fossil fern

The processes of organic maturation that occur during the permineralization of fossils and the detailed chemistry of the resulting products are incompletely understood. Primary among such processes is the geochemical alteration of biological matter to produce kerogen, such as that which comprises the cell walls of the fossils studied here: essentially unmetamorphosed, Eocene plant axes (specimens of the fossil fern Dennstaedtiopsis aerenchymata cellularly permineralized in cherts of the Clarno Formation of Oregon and the Allenby Formation of British Columbia). The composition and molecular structure of the kerogen that comprises the cell walls of such axes were analyzed using ultraviolet Raman spectroscopy (UV–Raman), solid state 13C nuclear magnetic resonance spectroscopy ( 13C NMR) and pyrolysis–gas chromatography–mass spectrometry (py–GC–MS). Cellularly well-preserved fern axes from both geologic units exhibit similar overall molecular structure, being composed primarily of networks of aromatic rings and polyene chains that, unlike more mature kerogens, lack large polycyclic aromatic hydrocarbon (PAH) constituents. The cell walls of the Allenby Formation specimens are, however, less altered than those of the Clarno chert, exhibiting more prevalent oxygen-containing and alkyl functional groups and comprising a greater fraction of rock mass. The study represents the first demonstration of the effectiveness (and limitations) of the combined use of UV–Raman, 13C NMR and py–GC–MS for the analysis of the kerogenous cell walls of chert-permineralized vascular plants.

Chemical Fingerprinting of Adhesive Tapes by GCMS Detection of Petroleum Hydrocarbon Products

Pressure-sensitive adhesive tapes often represent key evidence of crimes such as assault, rape or homicide; thus, the development of analytical techniques able to contribute to a detailed characterization of these materials is of forensic importance. The gas chromatography-mass spectrometry (GCMS) analysis of the solvent extractable fractions of a suite of electrical and gaffer adhesive tapes spanning a range of colors and manufacturers identified a number of petroleum-derived hydrocarbons. Molecular and isotopic analyses of hydrocarbon constituents of complex materials have found wide analytical utility including the forensic investigation of oil spills and arson. Here, we investigate the utility of these techniques for characterizing the hydrocarbon composition of pressure-sensitive adhesive tapes for forensic correlation purposes. Subtle distinction of tape samples was evident in the GCMS distribution of several hydrocarbon groups including alkyl-naphthalenes, hopane and sterane biomarkers. Linear discriminant analysis of the abundances of these products provided high level differentiation of tape manufacturer. The distinction of different adhesive tape samples was further extended by measurement of their stable carbon isotopic values. The molecular and isotopic differences of the petroleum content of tapes are consistent with the use of different petroleum materials used in the manufacturing process and demonstrate the benefits of the combined use of complementary oil hydrocarbon characterization approaches. This study reveals the forensic potential of using established petroleum characterization methods for characterizing materials with a petroleum-derived hydrocarbon element.

Citrus Essential Oil of Nigeria Part II Valencia Orange Leaf Oil Composition

Leaf oils from Valencia late and Campbell Valencia (Citrus sinensis (L) Osbeck cv. Valencia) obtained by hydrodistillation were analyzed using GC and GC-MS. Valencia late volatile oil gave thirty-four constituents, these accounted for 86.28 % of the total oil, while forty-four constituents representing 96.61 % of the total oil were identified in Campbell Valencia. Both oils were largely dominated by monoterpene hydrocarbons, 73.45 % in Campbell Valencia and 69.10 % in Valencia late. Sabinene (28.27–34.81 %) and ô-3-carene (10.81–13.86 %) were the major monoterpene hydrocarbon constituents in both oils. Oxygenated monoterpenes amounted to 16.46 % and 14.24 % of the total volatiles of Campbell Valencia and Valencia late respectively. In each oil linalool, terpinene-4-ol, neral and geranial were the main oxygenated monoterpenes. Sesquiterpene hydrocarbons accounted for 6.65 % and 2.95 % in Campbell and Valencia late oils, a-humulene (0.94–1.83 %), (E)-caryophellene (0.61–1.03 %) and ß-elemene (0.68–1.00 %) were the dominant sesquiterpenes.

Permeation of Carbon Dioxide and Methane Gases through Novel Silver-Incorporated Thin Film Composite Pebax Membranes

The selectivity of a membrane for CO2/CH4 separation is critical for purification of natural gas, landfill gas, and biogas since CO2 is the major impurity present in gas mixtures while CH4 is the major hydrocarbon constituent. The performance of poly(ether-block-amide) (Pebax 2533) membrane and its silver-incorporated form were investigated with respect to their permeation properties for these two gases. Thin-film composite (TFC) membranes of Pebax were prepared by dissolving 20 g of the polymer in 80 mL of 3:7 volumetric ratio of m-cresol/isopropanol solvent mixture, followed by casting on polyvinylidene fluoride (PVDF) ultrafiltration substrate. Silver incorporation was carried out by loading silver tetrafluoroborate (AgBF4) at 36% of the Pebax polymer weight in the same dope solution. Membranes were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) to study intermolecular interactions, crystalline nature, and surface and cross-sectional morphologies, respectively. At a feed pressure of 1 MPa, Pebax gave a CO2 permeance of 32.8 GPU at a CO2/CH4 selectivity of 15.3, whereas Ag-Pebax exhibited an enhanced selectivity of 36.2, even though its permeance was reduced to 12.1 GPU. The Ag-Pebax membrane was further upscaled as a spiral-wound module of 0.20 m2 effective area to test its commercial feasibility.

Validation of a FT-IR method for the determination of oils and grease in water using tetrachloroethylene as the extraction solvent

The term “Oils and Grease” (OG) encompasses a broad family of chemical compounds such as fatty material of biogenic origin, or petroleum hydrocarbon constituents. These compounds can cause environmental degradation and induce related public health risks when discharged in surface or ground waters. Consequently, OG is regulated by both European and National legislation for drinking water and wastewater. The development of methods for OG determination presents several difficulties and challenges for the analytical laboratory, since this parameter is methoddefined, i.e. the method establishes the measurand. Among several alternative methods that have been proposed in the literature, FT-IR determination after liquid–liquid extraction is known to be an easy, low-cost alternative for monitoring of OG at the ppm level. However, established FT-IR methods are based on Freon 113 extraction, a solvent which has been banned as an ozone depleting agent. This paper presents the development and validation of an in-house FT-IR method for the determination of OG in water that uses tetrachloroethylene as a Freon 113 substitute. The method was developed in EYDAP’s laboratories for the monitoring and control of OG in surface and drinking waters. Results regarding the calibration, linearity, OG recovery, precision, detection — quantitation limits and robustness are presented and discussed. Tetrachloroethylene proved to be a suitable alternative to Freon 113 and the method was deemed appropriate for monitoring oil spills or discharges in surface waters or in the drinking water network, at levels > 0.1 ppm.