Low Molecular Weight Aromatic Hydrocarbons Research Articles

Geological and geochemical characterization of caprock integrity in the Athabasca oilsands region

Caprocks play a pivotal role in petroleum systems for the accumulation of oil and gas, as well as in processes such as steam injection for heavy oil recovery and geological storage of CO2. In this study, the geological and geochemical characteristics of the caprock from the Cretaceous Wabiskaw Member (Mbr.) and overlying Clearwater Formation (Fm.), situated above the Athabasca oil sand region, were thoroughly examined using core samples obtained from well 1-22-90-14W4. Through HAWK programmed pyrolysis and solvent extraction, the caprock succession was revealed to exhibit limited organic content with total organic carbon content < 2.0 wt% and extractable organic matter (EOM) < 200 ppm. Further analysis using gas chromatography-flame ionization detector and gas chromatography-mass spectrometry on EOM unveiled insights into the mixing dynamics between the underlying oil reservoir and the caprock indigenous materials. Distinct trends in the ratios of low molecular weight (LMW) aromatic hydrocarbons, N-shielded carbazole, benzo[c]carbazole, and concentrations of carbazoles and benzocarbazoles were evident within a 5-m distance from the caprock-reservoir contact, indicating significant fractionation among compounds. Enrichment of these compounds was observed in the shale of the Wabiskaw Mbr., with a reversal of trends occurring within the initial 5 m into the overlying shale of the Clearwater Fm., suggesting limited oil penetration into the shale. The main Clearwater Fm. caprock succession was characterized by a dominance of immature, indigenous terrigenous organic matter, along with background concentrations of carbazole and benzocarbazole and an absence of N-shielded and/or LMW compound preferences. This composition starkly differed from the oil found in the underlying reservoir. The presence of calcareous cements in the Clearwater Fm. shale, approximately 5 m above the base, characterized by high bulk density (with 62% siderite), low porosity, and matrix permeability, contributed significantly to enhancing the sealing capacity of the caprock. The overall results provide compelling evidence that vertical oil leakage from the McMurray Fm. reservoir through the overlying shale of the Clearwater Fm. has not occurred during the post-lithification history with exception of the lower-most 5 m. The clay-rich argillaceous units identified in this study emerge as potential candidates for serving as effective caprock seals for steam injection and CO2 storage.

Characterization of chemical composition of high viscosity heavy oils: Macroscopic properties, and semi-quantitative analysis of molecular composition using high-resolution mass spectrometry

Heavy oil is an important resource in current petroleum exploitation, and the chemical composition information of heavy oil is crucial for revealing its viscosity-inducing mechanism and solving practical exploitation issues. In this study, the techniques of high-temperature gas chromatography and high-resolution mass spectrometry equipped with an electrospray ionization source were applied to reveal the chemical composition of typical heavy oils from western, central, and eastern China. The results indicate that these heavy oils display significant variations in their bulk properties, with initial boiling points all above 200 °C. Utilizing pre-treatment and ESI high-resolution mass spectrometry, an analysis of the molecular composition of saturated hydrocarbons, aromatic hydrocarbons, acidic oxygen compounds, sulfur compounds, basic nitrogen compounds, and neutral nitrogen compounds within the heavy oil was conducted. Ultimately, a semi-quantitative analysis of the molecular composition of the heavy oil was achieved by integrating the elemental content. The semi-quantitative analysis results of Shengli-J8 heavy oil and a conventional Shengli crude oil show that Shengli-J8 heavy oil lacks alkanes and low molecular weight aromatic hydrocarbons, which contributes to its high viscosity. Additionally, characteristic molecular sets for different heavy oils were identified based on the semi-quantitative analysis of molecular composition. The semi-quantitative analysis of molecular composition in heavy oils may provide valuable reference data for establishing theoretical models on the viscosity-inducing mechanism in heavy oils and designing viscosity-reducing agents for heavy oil exploitation.

Syntrophic Hydrocarbon Degradation in a Decommissioned Off-Shore Subsea Oil Storage Structure.

Over the last decade, metagenomic studies have revealed the impact of oil production on the microbial ecology of petroleum reservoirs. However, despite their fundamental roles in bioremediation of hydrocarbons, biocorrosion, biofouling and hydrogen sulfide production, oil field and oil production infrastructure microbiomes are poorly explored. Understanding of microbial activities within oil production facilities is therefore crucial for environmental risk mitigation, most notably during decommissioning. The analysis of the planktonic microbial community from the aqueous phase of a subsea oil-storage structure was conducted. This concrete structure was part of the production platform of the Brent oil field (North Sea), which is currently undergoing decommissioning. Quantification and sequencing of microbial 16S rRNA genes, metagenomic analysis and reconstruction of metagenome assembled genomes (MAGs) revealed a unique microbiome, strongly dominated by organisms related to Dethiosulfatibacter and Cloacimonadetes. Consistent with the hydrocarbon content in the aqueous phase of the structure, a strong potential for degradation of low molecular weight aromatic hydrocarbons was apparent in the microbial community. These degradation pathways were associated with taxonomically diverse microorganisms, including the predominant Dethiosulfatibacter and Cloacimonadetes lineages, expanding the list of potential hydrocarbon degraders. Genes associated with direct and indirect interspecies exchanges (multiheme type-C cytochromes, hydrogenases and formate/acetate metabolism) were widespread in the community, suggesting potential syntrophic hydrocarbon degradation processes in the system. Our results illustrate the importance of genomic data for informing decommissioning strategies in marine environments and reveal that hydrocarbon-degrading community composition and metabolisms in man-made marine structures might differ markedly from natural hydrocarbon-rich marine environments.

Assessment of aqueous cleaning of acrylic paints using innovative cryogels

Waterborne acrylic paints have been widely used by artists since their development in the late 50s. Their cleaning, i.e., the removal of mainly airborne dust and grime, is a challenging operation, because acrylics are very sensitive to solvents in a wide range of polarity. Even if aliphatic and low-molecular weight aromatic hydrocarbons are less prone to interact with the hydrophilic components of the acrylic paint layer, the use of water is necessary since it grants better cleaning performances. In this paper, three acrylic commercial paints from Liquitex® (USA) were selected and characterized using Fourier Transform Infrared spectroscopy (FT–IR) and pyrolysis – gas chromatography – mass spectrometry (Py-GC–MS). The removal of artificial soil from these paint films was carried out using novel highly retentive PVA-based cryogels that have been recently developed to avoid the uncontrolled wetting of water-sensitive artistic surfaces. Their cleaning efficiency was evaluated using Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR), Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM). Finally, an ATR-FTIR and 2D FTIR Imaging study about the residues left by the gels was carried out by comparing the cryogel with a Velvesil Plus® emulsion, a gel-like silicone polyether copolymer used in the recent past to create a stable water-in-oil emulsion, and still available on the market to conservators. In conclusion, the cryogel granted a safe and satisfactory cleaning action and a residue-free soil removal from acrylic paint films, overcoming the drawbacks of traditional cleaning methods.

Characterization of Petroleum Hydrocarbons in Post-Burn Crude Oil-Spilled Soils, Gokana, Rivers State, Nigeria

In the Niger delta, crude oil spilled soils are burned as a means of decontaminating the impacted soils. Gas chromatography - flame ionization detector (GCFID) analyses were performed on oil residues extracted from burnt spilled oil soil samples to facilitate detailed chemical composition and characterization of petroleum hydrocarbons. The concentrations of aliphatic hydrocarbons (AHCs) from C 13 to C 36 were low and range from 363.4 to 439.6 mg/kg, with hydrocarbons burning ≤ C 12 and the monocyclic aromatics – BTEX not detected in all the samples. Polycyclic aromatic hydrocarbon (PAH) concentrations, which ranged from 3236.6 to 4190.0 mg/kg, were significantly high and constituted from 88.26 to 91.25% of total petroleum hydrocarbon compositions in the burnt spilled oil soil samples. Petroleum hydrocarbon distribution profiles for the AHCs and PAHs were similar for all the samples and indicated similar alteration source. The compositions of AHCs were generally low, between 1.13 and 11.18%, while compositions of PAHs varied considerably from 0.17 to 30.50%. The composition of the 5-6 ring PAHs were between 3.94 - 4.65 times more than the 2-4 ring PAHs. From these results, the burning of spilled oil soils extensively degraded the AHCs and volatile low molecular weight aromatic hydrocarbons and generated significant amounts of 5-6 ring PAHs, some of which are carcinogenic.

Simultaneous Determination of Environmental Contaminants with Different Volatilities in Tap Water Samples Using a New Approach to Single-Drop Microextraction Procedure

A new single-drop microextraction approach is proposed for the extraction of compounds with a wide range of volatilities from tap water samples with separation/detection by gas chromatographymass spectrometry. This new microextraction mode is called direct immersion-headspace-single drop microextraction (DI-HS-SDME). Trihalomethanes (THMs), hydrocarbons with low molecular weight (benzene, ethyl benzene and xylenes) and polycyclic aromatic hydrocarbons (PAHs) were the model compounds. Ten milliliters of tap water samples and drop volume of 1.5 µL of 1-octanol were used. The optimal condition for DI-HS-SDME mode was 80 min of total extraction time (48 min at 40 °C in DI-SDME mode and 32 min at 12 °C in HS-SDME mode) and the addition of 1.2 g of NaCl. The analytical figures of merit were evaluated, the limits of detection ranged from 0.03 µg L-1 for o-xylene and ethyl benzene to 6 µg L-1 for THMs. The proposed method represents a promising alternative for the analysis of aqueous matrices which contain compounds with very different ranges of volatility.

Polystyrene degradation studies using Cu supported catalysts

Waste management of plastics through conversion into valuable hydrocarbons is in high demand. The degradation of WEPS was investigated in a Pyrex batch reactor using Cu metal, Cu-Al2O3, Cu-Mmn and Cu-AC catalysts. Catalysts with the maximum products were characterized for BET surface area and SEM in comparison to their supporting materials. Cu supported catalysts were found to increase the selectivity of low molecular weight aromatic hydrocarbons as compared to Cu metal and the supports. Among the supported catalysts, 20% Cu-Al2O3 was found to have moderate activity and high selectivity to yield desirable low molecular weight aromatic hydrocarbons. The BET surface area increased only in the case of 20% Cu-Al2O3, whereas the SEM images of 20% Cu-Al2O3 reveal aggregated porous structures with apparent active Cu metal which provide high surface area for the degradation of WEPS. The yield of styrene monomer was 60.48%, toluene 10.98%, ethylbenzene 9.92% and methylstyrene was 3.66% using 20% Cu-Al2O3 catalyst.

Thermo-catalytic pyrolysis of polystyrene in the presence of zinc bulk catalysts

Zinc bulk catalysts (Zn, ZnO and ZnCl2) were used for the thermo-catalytic pyrolysis of EPSW and were found with high activity and selectivity of products. Thermo-catalytic pyrolysis was carried out using an efficient Pyrex batch reactor. Zn metal catalyst was found as the best catalyst amongst the zinc bulk catalysts for the cost effective pyrolysis of EPSW (expanded polystyrene waste). The yield of liquid products at 450°C, 120min heating time and 1:0.2 feed to catalyst ratio was 96.73±0.12wt.% with 2.47wt.% toluene, 1.16wt.% ethylbenzene, 47.96wt.% styrene monomer and 1.90wt.% α-methylstyrene. The components of liquid products were separated by fractional distillation and found with further thermal pyrolysis in addition to cyclization and recombination reactions. During the fractional distillation, much product variations were observed. High molecular weight aromatic hydrocarbons decreased with the associated increase of low molecular weight aromatic hydrocarbons, particularly toluene and ethylbenzene.

The effect of origin and genetic processes of low molecular weight aromatic hydrocarbons in petroleum on their stable carbon isotopic compositions

Stable carbon isotopic compositions of individual low molecular weight aromatic hydrocarbons, such as alkylbenzenes, alkylnaphthalenes and alkylphenanthrenes, were measured from a set of oils, mostly from the North-West shelf of Australia, of varying age, facies type and thermal maturity. The objective was to assess the influence of thermal maturity and source during generation of these aromatics on their stable carbon isotopic compositions. For most of the oils studied, δ13C of the aromatic components show a 13C depletion as the degree of methylation increases. For the alkylnaphthalenes, the 13C depletion is most pronounced for low maturity oils compared to high maturity oils. δ13C of the methyl groups of these alkylnaphthalenes were calculated and the resulting data display significant differences between ‘mature’ and ‘immature’ oils, suggesting that isotopically lighter methyl groups are ‘released’ as thermal maturation proceeds. Therefore, we propose an isotopic fractionation associated with the methyl transfer mechanisms affecting low molecular weight aromatic hydrocarbons during diagenesis.

Identifying polycyclic aromatic hydrocarbon-degrading bacteria in oil-contaminated surface waters at Deepwater Horizon by cultivation, stable isotope probing and pyrosequencing

Polycyclic aromatic hydrocarbons (PAHs) are an important class of chemical pollutants that constitute a major component of total hydrocarbons in crude oils. Based on their poor water solubility, toxicity, persistence and potential to bioaccumulate, these compounds are recognized as high-priority pollutants in the environment and are of significant concern for human health. At oil-contaminated sites, PAH-degrading bacteria perform a critical role in the degradation and ultimate removal of these compounds. In April 2010, enormous quantities of PAHs entered the Gulf of Mexico from the thousands of tons of oil that were released from the ill-fated drilling rig Deepwater Horizon. In the ensuing months after the spill, intense research efforts were devoted to characterizing the microorganisms responsible for degrading the oil, particularly in deep waters where a large oil plume, enriched with aliphatic and low molecular-weight aromatic hydrocarbons, was found in the range of 1,000–1,300 m. PAHs, however, were found mainly confined to surface waters. This paper discusses efforts utilizing DNA-based stable isotope probing, cultivation-based techniques and metagenomics to characterize the bacterial guild associated with PAH degradation in oil-contaminated surface waters at Deepwater Horizon.

SPME-GCMS study of the natural attenuation of aviation diesel spilled on the perennial ice cover of Lake Fryxell, Antarctica

In January 2003, a helicopter crashed on the 5 m thick perennial ice cover of Lake Fryxell (McMurdo Dry Valleys, East Antarctica), spilling ~ 730 l of aviation diesel fuel (JP5-AN8 mixture). The molecular composition of the initial fuel was analyzed by solid phase microextraction (SPME) gas chromatography–mass spectrometry (GC–MS), then compared to the composition of the contaminated ice, water, and sediments collected a year after the spill. Evaporation is the major agent of diesel weathering in meltpool waters and in the ice. This process is facilitated by the light non-aqueous phase liquid properties of the aviation diesel and by the net upward movement of the ice as a result of ablation. In contrast, in sediment-bearing ice, biodegradation by both alkane- and aromatic-degraders was the prominent attenuation mechanism. The composition of the diesel contaminant in the ice was also affected by the differential solubility of its constituents, some ice containing water-washed diesel and some ice containing exclusively relatively soluble low molecular weight aromatic hydrocarbons such as alkylbenzene and naphthalene homologues. The extent of evaporation, water washing and biodegradation between sites and at different depths in the ice are evaluated on the basis of molecular ratios and the results of JP5-AN8 diesel evaporation experiment at 4 °C. Immediate spread of the aviation diesel was enhanced where the presence of aeolian sediments induced formations of meltpools. However, in absence of melt pools, slow spreading of the diesel is possible through the porous ice and the ice cover aquifer.

Photochemical transformations of water-soluble fraction (WSF) of crude oil in marine waters: A comparison between photolysis and accelerated degradation with TiO 2 using GC–MS and UVF

Changes in the chemical nature of the water-soluble fraction (WSF) of crude oils caused by photolysis and heterogeneous photocatalysis using TiO 2 were investigated by gas chromatography–mass spectrometry (GC–MS) and ultraviolet fluorescence spectrophotometry (UVF). Two Brazilian crude oil samples with different concentrations of WSF (45 and 15 mg C l −1) were studied. Photochemical driven reactions were investigated under UV-Vis irradiation in the absence and in the presence of the photocatalyst. The presence of aromatic hydrocarbon in the WSF before irradiation, resulting from crude oil slick solubilization on seawater, was confirmed by chromatograms that showed a series of low molecular weight aromatic hydrocarbons together with a unresolved complex mixture (UCM). However, in the irradiated WSF these compounds were not detected. After 6 days photolysis period, WSF from both crude oils did not show peaks of aromatic compounds, whereas the presence of long chains unsaturated hydrocarbons as well as sulfur compounds were detected. In contrast, when TiO 2 was employed, complete photodegradation of both crude oil samples in the WSF occurred after very short light exposure periods (1–2 days). Quantitative data were also obtained and discussed here. The results reinforce photodegradation as an effective weathering process for the transformation of dissolved crude oil fraction, particularly in high solar radiation environments. Complete degradation in a short period of time was only made possible by heterogeneous photocatalysis.

Physiological responses of Avicennia marina seedlings to the phytotoxic effects of the water-soluble fraction of light Arabian crude oil

Stomatal behavior, growth performance and the accumulation of polynuclear aromatic hydrocarbons (PAHs) were evaluated in seedlings of the mangrove Avicennia marina (Forssk.) Vierh., treated with a water-soluble fraction (WSF) of Abu-Dhabi light Arabian crude oil through foliar spraying or soil application. Irregular stomatal behavior and weak stomatal control over transpiration were observed during the first 24 hours, where stomatal resistances of plants sprayed with 150 and 300 μg PAHs plant−1 were significantly lower than that of the control plants. After six weeks, all treated plants showed no significant difference in their relative growth rate (RGR) or in the net assimilation rate (NAR) compared with the control plants. Tri-aromatic hydrocarbons were the most accumulated in tissues of the treated plants. Penta- and hexa-aromatics, on the other hand, were undetectable in the WSF and consequently in the treated plants. A linear relationship was observed between the dose applied to plants and the amounts of tissue accumulated PAHs (r 2=0.515 for soil application and r 2=0.984 for foliar spray). In plants sprayed with 300 μg PAHs plant−1, the total PAHs accumulated were more than that accumulated in plants treated through soil application. These findings suggest that: aqueous extraction of crude oil tends to signify the percentage of the low molecular weight PAHs, e.g. naphthalene, to the total PAHs; disturbed stomatal behavior in the first day of the treatment may be due to the venting of the volatile low molecular weight aromatic hydrocarbons (e.g. benzene, toluene, and xylenes) through the stomata; and uptake of water-soluble hydrocarbons by plants is equally possible through both of the root system and the foliage. The ecological implications of these finding are discussed in relation to oil pollution of mangrove stands under field conditions.

Phytotoxicity of ancient gaswork soils. Effect of polycyclic aromatic hydrocarbons (PAHs) on plant germination

The phytotoxicity of various contaminated soils was assessed by plant inventories on ancient industrial fields and by phytotoxicity tests. Industrial fields are well colonised by numerous weedy plants. Phytotoxicity was tested with pure PAHs, ancient industrial soils, soil leaches, liquid tar and tar volatile compounds. Both field studies and toxicity tests show that contaminated samples can be classified into two categories: first, a recently excavated soil/liquid tar that was foul-smelling and phytotoxic and second, an ‘aged’, surface soil that was weathered and non-phytotoxic. Plant germination and growth are strongly inhibited by the presence of volatile, water-soluble low molecular-weight hydrocarbons (<3 rings) such as benzene, toluene, xylene (BTX), styrene, indene, naphthalene and other possibly toxic substances. On the other hand, high molecular weight PAH (3–5 rings) did not show any phytotoxicity under the conditions studied. These findings suggest that once low molecular weight aromatic hydrocarbons are removed, e.g. by volatilization, biodegradation, weathering, tillage and fertilising, plants should be able to grow.

Quantitative Analysis of Fuel-Related Hydrocarbons in Surface Water and Wastewater Samples by Solid-Phase Microextraction

Solid-phase microextraction (SPME) parameters were examined on water contaminated with hydrocarbons including benzene and alkylbenzenes, n-alkanes, and polycyclic aromatic hydrocarbons (PAHs). Absorption equilibration times ranged from several minutes for low molecular weight compounds such as benzene to 5 h for high molecular weight compounds such as benzo[a]pyrene. Under equilibrium conditions, SPME analysis with GC/FID was linear over 3-6 orders of magnitude, with linear correlation coefficients (r(2)) greater than 0.96. Experimentally determined FID detection limits ranged from ∼30 ppt (w/w hydrocarbon/sample water) for high molecular weight PAHs (e.g., MW > 202) to ∼1 ppb for low molecular weight aromatic hydrocarbons. Experimental distribution constants (K) were different with 100- and 7-μm poly(dimethylsiloxane) fibers, and poor correlations with previously published values suggest that K depends on the fiber coating thickness and the sorbent preparation method. The sensitivity of SPME analysis is not significantly enhanced by larger sample volumes, since increasing the water volume (e.g., from 1 to 100 mL) has little effect on the number of analyte molecules absorbed by the fiber, especially for compounds with K < 500. Water sample storage should utilize silanized glassware, since hydrocarbon losses up to 70% could be attributed to unsilanized glassware walls when samples were stored for 48 h. Hydrocarbon losses at part-per-billion concentrations also occurred with surface waters due to partitioning onto part-per-thousand concentrations of suspended solids. Quantitative determinations of aromatic and aliphatic hydrocarbons (e.g., in gasoline-contaminated water) can be performed using GC/MS with deuterated internal standard or standard addition calibration as long as the target components or standards had unique ions for quantitation or sufficient chromatographic resolution from interferences. SPME analysis gave good quantitative performance with surface waters having high suspended sediment contents, as well as with coal gasification wastewater which contained matrix organics at 10(6)-fold higher concentrations than the target aromatic hydrocarbons. Good agreement was obtained between a 45-min SPME and methylene chloride extraction for the determination of PAH concentrations in creosote-contaminated water, demonstrating that SPME is a useful technique for the rapid determination of hydrocarbons in complex water matrices.

Hydrocarbon pollution from marinas in estuarine sediments

A measure of the impact of marinas on three Eastern Virginia estuarine creeks was obtained by a study of hydrocarbons in their sediments. Two of the creeks support considerable marine activity, including pleasure boat marinas, boat repair facilities, and commercial fishing operations. The third creek, which served as a control, is seldom used by boats, and is surrounded by marsh and woodland. Sediments from the creeks with marinas contained significantly higher levels of both aromatic and aliphatic hydrocarbons than did the control. Differences in the concentrations of certain oil-pollution indicators, such as the 17α,21β-hopane homologs and phytane, and low molecular weight aromatic hydrocarbons, are indicative of light petroleum fractions. Most of the aromatic hydrocarbons from all creeks, however, appear to have a pyrogenic origin. Although hydrocarbons from three probable origins (petroleum, pyrogenesis, and recent biosynthesis) were detected in all locations, the petroleum-derived and pyrogenic hydrocarbons were of only minor importance relative to the biogenic hydrocarbons in the control creek.

Exposure of phytoplankton to ekofisk crude oil

Solutions of Ekofisk crude oil in sea water were prepared by slow stirring for 21h in a closed system. Headspace and GC/MS techniques were applied to establish dose composition and levels. The standardized test medium produced in a closed system contained approximately 14 mg oil per litre and was dominated by low molecular weight aromatic hydrocarbons and phenols. The toxicity of the standarized oil-containing medium to three marine diatoms was studied in a cage culture turbidostat and by conventional batch culture technique. The three algal species differed in sensitivity to the oil compounds, but showed identical ranking in both test systems. Standardized test medium diluted to 50% with respect to oil content stopped the growth of the most sensitive alga, Skeletonema costatum. For comparison naphthalene was applied and gave 50 % growth reduction at a concentration of 400 μg litre −1. The growth of Chaetoceros ceratosporum was only slighty affected by the full strength standard test medium, which had no influence on the growth of Phaeodactylum tricornutum, the least sensitive organism. The presence of an oil layer on the surface of the standard test medium during the growth test greatly increased its toxicity and blocked completely the photosynthesis even of P. tricornutum after 4 days.

The disposition of aromatic hydrocarbons in adult spot shrimp (Pandalus platyceros) and the formation of metabolites of naphthalene in adult and larval spot shrimp

1. Adult spot shrimp (Pandalus platyceros) exposed to 110 p.p.b. (microgram/ml) of the water-soluble fraction of Prudhoe Bay crude oil for one week accumulated a variety of low-molecular weight aromatic hydrocarbons (primarily C1-C5 substituted derivatives) in thoracic and abdominal tissues. 2. Adult and larval spot shrimp were exposed to 3H- and 14C- labelled naphthalene (a component of the water-soluble fraction) in seawater to delineate the types of metabolites formed. Both adults and larvae converted naphthalene to conjugated and non-conjugated structures such as the glucuronide, sulphate, dihydrodiol and phenolic derivatives. The presence of a quinone was also indicated.

Low molecular weight aromatic hydrocarbons in drinking water

Abstract As part of the survey of organic compounds in Ontario drinking waters, several aromatic hydrocarbons were identified in the finished water of a water treatment plant. Benzene and alkylbenzenes were quantitated at the parts per trillion level (ng/1) whereas analysis of the raw water failed to show the presence of any aromatic hydrocarbons. Experimental evidence is presented that suggests that relatively high concentration of the aromatics may occasionally contaminate the raw water which enters the water treatment plant. These aromatics are initially adsorbed on the filter media, and gradually released into the finished water.

Low molecular weight aromatic hydrocarbons in gas condensates from Alberta, Canada

Forty one gas condensates from Alberta, Canada, from stratigraphie units ranging in age from U. Cretaceous to M. Devonian were gas chromatographically analysed for low molecular weight aromatic hydrocarbons. Aromatic hydrocarbons range from 0.5 to 45.6 per cent with benzene, toluene and the xylenes averaging 80 per cent of the aromatic content. Trimethylbenzenes (of which 1,2,4-trimethylbenzene is the most important), ethylbenzene, and naphthalene comprise the major portion of the remainder. Other alkyl substituted benzenes and naphthalenes are relatively insignificant. Factor analysis demonstrated relations amount the low molecular weight aromatic hydrocarbons, n-paraffins and sulphur. These relations are interpreted in terms of the derivation of toluene and xylenes from precursors such as the carotenes, with subsequent temperaturecontrolled disproportionation of both toluene and xylenes to yield benzene and trimethylbenzenes. Although the relative positions of benzene, toluene, xylenes and trimethylbenzenes on one hyperplane are in the same relative proportions as their free energies of formation, they are not in thermodynamic equilibrium. These positions may be interpreted also as proportional to their solubilities. Study of the distribution of the xylene and trimethylbenzene isomers suggests the dominance of specific precursors. Ethylbenzene abundance is independent of the abundance of other low molecular weight aromatic hydrocarbons, and probably arises from phenylalanine or tyrosine by decarboxylation, deamination, and conversion of vinylbenzene to ethylbenzene. Naphthalene may have a source distinct from that of benzene and the methylsubstituted benzenes.