Merv Fingas

Oil spill identification

Abstract To unambiguously identify spilled oils and petroleum products and to link them to the known sources are extremely important in settling questions of environmental impact and legal liability. This article briefly reviews the most recent development and advances of chemical fingerprinting and data interpretation techniques which are most frequently used in oil spill identification studies, including recognition of relative distribution patterns of petroleum hydrocarbons, analysis of ‘source-specific marker’ compounds, determination of diagnostic ratios of specific oil constituents, isotopic analysis, and several other emerging techniques. The issue of how biogenic and pyrogenic hydrocarbons are distinguished from petrogenic hydrocarbons is also addressed. Finally, the example of the Exxon Valdez spill is reviewed to illustrate how complex hydrocarbon mixtures were identified and allocated to multiple sources by using these advanced chemical fingerprinting techniques.

Comparison of oil composition changes due to biodegradation and physical weathering in different oils

The well-characterized Alberta Sweet Mixed Blend oil and several other oils which are commonly transported in Canada were physically weathered and then incubated with a defined microbial inoculum. The purpose was to produce quantitative data on oil components and component groups which are more susceptible or resistant to biodegradation, and to determine how oils rank in relation to each other in terms of biodegradation potential. The biodegraded oils were characterized by quantitative determination of changes in important hydrocarbon groups including the total petroleum hydrocarbons, total saturates and aromatics, and also by quantitation of more than 100 individual target aliphatic, aromatic and biomarker components. The study reveals a pattern of distinct oil composition changes due to biodegradation, which is significantly different from the pattern due to physical or short-term weathering. It is important to be able to distinguish between these two forms of loss, so that loss due to weathering is not interpreted as loss due to biodegradation in the laboratory or in the field. Based on these findings, the oil composition changes due to biodegradation can be readily differentiated from those due to physical weathering. To rank the tested oils with respect to biodegradability, losses in total petroleum hydrocarbons and aromatics were used to calculate biodegradation potential indices, employing equations proposed by Environment Canada and the US National Oceanic and Atmospheric Administration. The different methods produced very similar biodegradation trends, confirming that patterns of oil biodegradability do exist.

Study of 22-year-old arrow oil samples using biomarker compounds by GC/MS

A GC/MS method for the characterization of 22-year-old spilled Arrow oil is described. After 22 years of weathering in the environment, most saturated hydrocarbons and polycyclic aromatic hydrocarbons in most Arrow oil samples have been lost. Their fingerprint give little information of the source, characteristics, and fate of the spilled oil. However, the method using biomarker compounds by GC/MS offers the distinct advantages of being better able to withstand interference from heavy weathering effects and to identify and match the spilled oil source. From 11 intertidal sediment samples collected from the shorelines of Chedabucto Bay, 47 triterpanes and steranes were positively identified. The relative abundance ratios of several pairs of triterpane and sterane compounds, especially the ratio of C[sub 29]/C[sub 30] hopanes that are displayed as major peaks in the m/z 191 ion chromatograms, are apparently independent of weathering effects and are unambiguously used for identifying the source of the 22-year-old Arrow oil samples. 27 refs., 8 figs., 6 tabs.

Forensic Fingerprinting of Biomarkers for Oil Spill Characterization and Source Identification

Biomarkers are one of the most important hydrocarbon groups in petroleum. Biomarkers can be detected in low quantities (ppm and sub-ppm level) in the presence of a wide variety of other types of petroleum hydrocarbons by the use of the gas chromatography/mass spectrometry (GC/MS). Relative to other hydrocarbon groups in oil such as alkanes and most aromatic compounds, biomarkers are more degradation-resistant in the environment. Furthermore, biomarkers formed under different geological conditions and ages may exhibit different biomarker fingerprints. Therefore, chemical analysis of biomarkers generates information of great importance to environmental forensic investigations in terms of determining the source of spilled oil, differentiating and correlating oils, and monitoring the degradation process and weathering state of oils under a wide variety of conditions. This article briefly reviews biomarker chemistry, biomarker characterization and quantification, biomarker distributions, weathering effects on biomarker composition, bicyclic biomarker sesquiterpanes and diamondoids, diagnostic ratios and cross-plots of biomarkers, unique biomarkers, application of biomarker fingerprinting techniques for spill source identification, and application of multivariate statistical analysis for biomarker fingerprinting.

Developments in the analysis of petroleum hydrocarbons in oils, petroleum products and oil-spill-related environmental samples by gas chromatography

This review gives a brief survey and comparison of chemical fingerprinting techniques by gas chromatography that are currently used for the characterization of petroleum hydrocarbons, the identification of oil spills and in assessing environmental impacts. This review focuses on new trends and developments in oil analysis methods.

Differentiation of the source of spilled oil and monitoring of the oil weathering process using gas chromatography-mass spectrometry

Abstract Methods described use high-performance capillary gas chromatography-mass spectrometry (GC-MS) operating mainly in the selected-ion monitoring (SIM) mode for oil analysis. The methods have been applied to the characterization of crude oils, weathered oils, biodegradation oils, and oil-spill-related environmental samples with different compositions, nature, and concentrations. Using GC-MS enables the identification and quantitation of specific target petroleum hydrocarbons including C8 through C40 normal alkanes, the isoprenoids, BTEX and alkyl benzene, target polycyclic aromatic hydrocarbons (PAHs) and their alkylated homologues, and biomarker triterpanes and steranes. The analysis of these target compounds and/or compound groups is important and essential for oil-spill monitoring. The analytical data have been successfully used for the differentiation of oils, tracking the source of long-term spilled oils, monitoring the oil weathering and biodegradation process under variable environmental conditions, and the determination of the weathering percentages of very heavily weathered oil samples by the selective use of biomarker parameters. Compared to some other traditional methods which were originally designed for industrial waste and hazardous waste, the methods described here are more selective and give a better representation of the true oil composition, and hence are more defensible.

Chemical characterization of crude oil residues from an arctic beach by GC/MS and GC/FID

A complete `total oil analysis method` suitable for monitoring chemical composition changes and studying the fate of 12-year-old weathered oil residues from an arctic beach is described. The characterizations not only are through analyses of individual aliphatic, aromatic, and biomarker compounds but also are through `pattern recognition` plots involving more than 100 important oil components and component groupings. The weathered percentages of residual oil in Baffin Island oil spill samples are quantified using C{sub 29} and C{sub 30} {alpha}{beta}-hopane in the fresh` source oil as internal oil references. The values of the weathered percentages show excellent correlation to the total solvent-extractable materials (TSEM), total petroleum hydrocarbons (TPH), aliphatic, aromatic, and biomarker compound analysis results. Biodegradation is demonstrated to have played an important role in the degradation and removal of the residual oil. Twelve years after the spill, the composition changes due to weathering progress much more slowly, and this slower rate of change will continue under these arctic conditions. 31 refs., 8 figs., 5 tabs.

Headspace solid phase microextraction (HSSPME) for the determination of volatile and semivolatile pollutants in soils.

We have investigated the use of headspace solid phase microextraction (HSSPME) as a sample concentration and preparation technique for the analysis of volatile and semivolatile pollutants in soil samples. Soil samples were suspended in solvent and the SPME fibre suspended in the headspace above the slurry. Finally, the fibre was desorbed in the Gas Chromatograph (GC) injection port and the analysis of the samples was carried out. Since the transfer of contaminants from the soil to the SPME fibre involves four separate phases (soil-solvent-headspace and fibre coating), parameters affecting the distribution of the analytes were investigated. Using a well-aged artificially spiked garden soil, different solvents (both organic and aqueous) were used to enhance the release of the contaminants from the solid matrix to the headspace. It was found that simple addition of water is adequate for the purpose of analysing the target volatile organic chemicals (VOCs) in soil. The addition of 1 ml of water to 1 g of soil yielded maximum response. Without water addition, the target VOCs were almost not released from the matrix and a poor response was observed. The effect of headspace volume on response as well as the addition of salt were also investigated. Comparison studies between conventional static headspace (HS) at high temperature (95 degrees C) and the new technology HSSPME at room temperature ( approximately 20 degrees C) were performed. The results obtained with both techniques were in good agreement. HSSPME precision and linearity were found to be better than automated headspace method and HSSPME also produced a significant enhancement in response. The detection and quantification limits for the target VOCs in soils were in the sub-ng g(-1) level. Finally, we tried to extend the applicability of the method to the analysis of semivolatiles. For these studies, two natural soils contaminated with diesel fuel and wood preservative, as well as a standard urban dust contaminated with polyaromatic hydrocarbons (PAHs) were tested. Discrimination in the response for the heaviest compounds studied was clearly observed, due to the poor partition in the headspace and to the slow kinetics of all the processes involved in HSSPME.

Solid-Phase Microextraction and Headspace Solid-Phase Microextraction for the Determination of Polychlorinated Biphenyls in Water Samples

A solid-phase microextraction (SPME) method has been developed for the quantification of polychlorinated biphenyls (PCBs) in water samples. Parameters such as sampling time, volume of water, volume of headspace, temperature, addition of salts, and agitation of the sample were studied. Because the time for reaching equilibrium between phases takes several hours or days, depending on the experimental conditions, it was necessary to work in nonequilibrium conditions to keep the sample analysis to a reasonable time. The possibility of sampling the headspace over the water sample (HSSPME), instead of immersing the fiber into the water (SPME), was also investigated, and despite the low partition of PCB into the headspace, HSSPME offered higher sensitivity than SPME at 100 °C. The adsorption kinetics for SPME at room temperature, SPME at 100 °C, and HSSPME at 100 °C were investigated and compared. The proposed HSSPME method exhibits excellent linearity and sensitivity. The detection limit was in the sub-ng/L level. This method has been applied to a real industrial harbor water and compared with liquid-liquid extraction. Both techniques offered similar results, but HSSPME was much more sensitive and considerably faster, by eliminating all the manual process intensive sample workup, and reduces solvent consumption entirely. The only drawback was that matrix effects were observed, but with the addition of deuterated surrogates to the sample or the use of a standard addition calibration, accurate quantification can be achieved.

Use of Methyldibenzothiophenes as Markers for Differentiation and Source Identification of Crude and Weathered Oils

A reliable, effective, and accurate gas chromatographic/mass spectrometric (GC/MS) method for differentiation and source identification of crude and weathered oils by the use of isomeric methyldibenzothiophene (C 1 -DBT) compounds is described. The method complements existing methods useful for oil characterization, but has its own distinct advantages: (1) C 1 -DBT isomers are present in all tested crude oils at relatively high concentrations and their distribution fingerprints vary significantly ; (2) C 1 -DBTs are chromatographicallywell-separated and resolved with minimal interference from other ions, and therefore the ratios of the isomeric C 1 -DBT compounds can be accurately determined ; (3) the relative distributions of C 1 -DBTs are subject to little interference from evaporative weathering in short-term or lightly weathered oils. However, the ratios are altered by biodegradation. Hence, this method can be distinctively used to indicate the occurrence of microbial degradation of oils. The effectiveness and usefulness of this method for oil source identification and differentiation and for oil weathering and biodegradation studies have been demonstrated by determination of the relative distributions of C 1 -DBTs in various samples including crude, weathered, burn, and biodegradation oil samples.