Mike Landriault

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.

Chemical Fingerprints of Alberta Oil Sands and Related Petroleum Products

Alberta oil sands are known to contain the worlds largest reserves of bitumen. The rapid growth in their production could result in a significant environmental impact. Fingerprinting bitumen and petroleum products from the Alberta oil sands is essential in order to better understand the chemical compositions of oil sands, prepare for potential oil spills, and address the associated environmental problems. This study presents an integrated quantitative chemical characterization of Alberta oil sands bitumen and other related Alberta oils using gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). The characterized target hydrocarbons include n-alkanes, unsubstituted polycyclic aromatic hydrocarbons (PAHs) and their alkylated homologues (APAHs), biomarker terpanes and steranes, bicyclic sesquiterpanes, and diamondoids. The chemical features of bitumen in oil sands are clearly distinguishable from those of most other conventional crude oils. The chemical fingerprints of diluted oil sands bitumen and Albian Heavy Synthetic crude were significantly altered by either the diluent blended with the former or the upgrading processing of crude bitumen in the latter. A chromatographic hump of unresolved complex mixtures (UCMs) eluting between n-C10 to n-C40 is pronounced and n-alkanes are nearly absent in bitumen extracted from oil sands. Alkylated naphthalenes account for only a small proportion of the total APAHs in Alberta oil sands extracts. The PAH compounds in oil sands extracts and diluted bitumen are dominated by alkylated homologues with the relative distribution of C0– < C1– < C2– < C3– for all five APAH series. Biomarker terpanes and cage-like adamantanes were determined in almost identical abundance and distribution profile in oil sands extracts and diluted crude bitumen, while biomarker steranes and bicyclic sesquiterpanes were removed to varying degrees by physical weathering or biodegradation.

Characteristics of bicyclic sesquiterpanes in crude oils and petroleum products

This study presents a quantitative gas chromatography-mass spectrometry analysis of bicyclic sesquiterpanes (BSs) in numerous crude oils and refined petroleum products including light and mid-range distillate fuels, residual fuels, and lubricating oils collected from various sources. Ten commonly recognized bicyclic sesquiterpanes were determined in all the studied crude oils and diesel range fuels with principal dominance of BS3 (C(15)H(28)), BS5 (C(15)H(28)) and BS10 (C(16)H(30)), while they were generally not detected or in trace in light fuel oils like gasoline and kerosene and most lubricating oils. Laboratory distillation of crude oils demonstrated that sesquiterpanes were highly enriched in the medium distillation fractions of approximately 180 to 481 degrees C and were generally absent or very low in the light distillation fraction (boiling point to approximately 180 degrees C) and the heavy residual fraction (>481 degrees C). The effect of evaporative weathering on a series of diagnostic ratios of sesquiterpanes, n-alkanes, and biomarkers was evaluated with two suites of weathered oil samples. The change of abundance of sesquiterpanes was used to determine the extent of weathering of artificially evaporated crude oils and diesel. In addition to the pentacyclic biomarker C(29) and C(30) alphabeta-hopane, C(15) and C(16) sesquiterpanes might be alternative internal marker compounds to provide a direct way to estimate the depletion of oils, particularly diesels, in oil spill investigations. These findings may offer potential applications for both oil identification and oil-source correlation in cases where the tri- to pentacyclic biomarkers are absent due to refining or environmental weathering of oils.

GC/MS Quantitation of Diamondoid Compounds in Crude Oils and Petroleum Products

This study presents a quantitative gas chromotography/mass spectrometry (GC/MS) method for the analysis of adamantane, diamantane, and their alkylated homologues in 14 crude oils and 22 petroleum products including light and mid-range distillate fuels, residual fuels, and lubricating oils collected from various sources. The method detection limits for five target diamondoids were in the range of 0.06 to 0.14 μ g/g oil. The total concentration of adamantane and its 16 alkylated homologues commonly range from approximately 40 to 500 μ g/g in most crude oils and from 0.6 to 1,300 μ g/g in refined products, but reaching values of up to 2,000 μ g/g for the south Louisiana crude oil and the Jet A fuel. Diamantanes occur in all crude oils and lighter to middle distillates, and their total concentration was in a range of 5 to 200 μ g/g and with maximum values near 600 μ g/g in weathered diesel fuel, but they were not detected in very light distillates and most lubricating oils. Laboratory distillation of crude oils demonstrated that adamantane series were highly enriched in the diesel distillation range between 180 to 287°C, while diamantanes were largely found in the distillation fraction from 280 to 320°C. The concentrations of five groups of biomarker compounds in the saturated hydrocarbon fraction decrease in the order of sesquiterpanes > terpanes ≥ steranes > adamantanes > diamantanes for most crude oils, while their concentrations in various refined products differ widely. The absolute concentrations of diamondoid compounds and their molecular indices offer potential diagnostic means for oil source identification and oil correlation, particularly for lighter refined products such as jet and diesel fuels in which the high molecular weight biomarkers have been removed during the refining processes.

Development of a methodology for accurate quantitation of alkylated polycyclic aromatic hydrocarbons in petroleum and oil contaminated environmental samples

Polycyclic aromatic hydrocarbons (PAHs) are compounds of concern because most of these compounds are toxic, carcinogenic, or mutagenic and are relatively persistent in the environment. Reliable quantitative information of PAHs is important to evaluate the acute and chronic harmful effects of PAHs on the ecosystem. Crude oils and refined petroleum products contain many highly abundant PAHs and heterocyclic PAHs, in particular the alkylated homologues of naphthalene, phenanthrene, dibenzothiophene, fluorene and chrysene (APAH). The alkylated PAH homologues usually occur in significantly higher concentrations than their corresponding unsubstituted parent PAHs. Petrogenic alkylated PAHs generally consist of large numbers of isomers. Unlike those individual unsusbstituted PAHs, most of the APAH isomers are not commercially available. Therefore, historically, the target APAHs are generally quantified using the relative response factors (RRFs) obtained from their respective unsubstituted parent PAH compounds, this inevitably results in the quantitative results of APAH being significantly underestimated. In order to improve the accuracy of the measurement of PAHs and their alkylated homologues in oil and oil related samples, this study measured and compared the response factors of a large number of alkylated PAHs relative to the internal standards in gas chromatography-mass spectrometry (GC-MS) analysis, with the goal of developing a more accurate quantitative methodology for the determination of oil APAHs, and eventually leading to a standardized methodology of quantitative APAH analysis. The PAHs in different oils and related environmental samples collected from oil impacted areas were determined using this GC-MS methodology. Furthermore, the influence of the measurement methodology on the diagnostic ratios of target PAHs was also assessed in this work.

Application of Light Petroleum Biomarkers for Forensic Characterization and Source Identification of Spilled Light Refined Oils

Light petroleum biomarkers such as bicyclic sesquiterpanes and diamondoids are ubiquitous components of crude oils and ancient sediments, and are also widely found in intermediate petroleum distillates and many finished petroleum products. These compounds are relatively resistant to biodegradation and light-to-medium evaporation weathering, thus particularly useful in oil-source correlation and differentiation for those cases where the traditional tri- to pentacyclic biomarkers are absent. This work utilized sesquiterpanes and diamondoids for fingerprinting and identification of light oils spilled on water. The gas chromatography/flame ionization detection (GC/FID) analysis and distribution profiles of polycyclic aromatic hydrocarbon (PAHs) and conventional biomarkers suggest that the spilled oils are mixtures of mainly gasoline and light diesel type fuel. Since potential source oil candidates were not available, and a large part of the hydrocarbons in gasoline and diesel co-eluted in chromatographic analysis, it is a challenge to quantify the gasoline and diesel in spill samples. It has been known from previous studies that the bulk concentrations of C14 to C16 sesquiterpanes are in the range of approximately 6,000 to 9,000 μg/g for many light diesel fuels, while little or no sesquiterpanes were detected in gasoline, light kerosene and heavy-end lubricating oils. The target sesquiterpanes in the spilled oil samples were determined to be in quite high concentrations: approximately 4,000 μg/g oil. Therefore, it was estimated that these spilled oil samples consist of approximately half gasoline and half light diesel. To verify the estimation, spilled samples were simulated by mixing a fresh gasoline and a light diesel with a similar carbon range as the spilled oils. Results from comparison of GC/FID chromatograms of the spilled oils with the simulated spill samples are consistent with that obtained from sesquiterpane analysis.

Determination of polar impurities in biodiesels using solid-phase extraction and gas chromatography-mass spectrometry.

This paper reports on a method for development and validation for simultaneous characterization and determination of oxygenated polar impurities--free fatty carboxylic acids (FFAs), partial glycerides (monoacylglycerides, MGs), residual glycerol and free sterols--in various biodiesels based on the combination of solid-phase extraction (SPE), silylation and GC/MS technologies. The effects of various SPE and silylation conditions on the method recoveries were evaluated. Using this integrated SPE-GC/MS method, 38 target polar compounds (13 FFAs, 17 glycerides and 8 sterols) in 9 biodiesels derived from 4 different feedstocks were successfully separated and quantified. It was found that the carbon chain length of FFAs was ranged from C(6) to C(24), with C(16) and C(18) being the most abundant in all biodiesels. The total FFAs concentration was consistent with the acid values (AVs) measured by standard method ASTM D974-04. MG congeners with carbon number of 18 (mono-C18) were most abundant in the biodiesel samples, followed by mono-C(16) and free glycerol. β-Sitosterol and campesterol were found to be the prevailing phytosterols in all pure vegetable oil-based biodiesels, while brassicasterol and stigmasterol was only significant in the biodiesel from canola oil and soybean oil, respectively, and abundant cholesterol was only detected in animal fat-based biodiesels.

Oil fingerprinting analysis using commercial solid phase extraction (SPE) cartridge and gas chromatography-mass spectrometry (GC-MS)

This study used solid phase extraction (SPE) cartridges for rapid cleanup and fractionation of oil samples in oil fingerprinting analysis. A series of commercially available florisil cartridges, normal phase SPE cartridges, and silica gel/cyanopropyl (SiO2/C3-CN) SPE cartridges was selected for the fractionation of oil into aliphatic and aromatic hydrocarbons. The florisil cartridges and normal phase SPE cartridges can clean up the oil samples but are unable to separate them into two fractions. The SiO2/C3-CN (1 g/0.5 g) SPE cartridge successfully separated oil samples into aliphatic and aromatic fractions by eluting with 4 mL of hexane and 4 mL of dichloromethylene (DCM)/hexane (3 : 1, v:v), respectively. No cross-elution was observed between aliphatic and aromatic fractions when oil loading mass was less than 40 mg on the SiO2/C3-CN SPE cartridge. The relative standard deviation (RSD) of five replicates of SPE-GC-MS analysis of 5 mg of reference oil is 2.8%, 1.2%, and 6.9% for total n-alkanes, polycyclic aromatic hydrocarbons (PAHs), and biomarkers, respectively. The recoveries of six spiked deuterated surrogates were all above 95%. This SPE-GC-MS method was used for the fingerprinting analysis of various crude oils, refined petroleum products, and environmental sediment samples. The characterized target hydrocarbons included n-alkanes, unsubstituted priority PAHs and alkylated homologues, and biomarker terpanes and steranes. The concentration profiles and diagnostic ratios of target compounds are both comparable to those obtained by the conventional silica gel column-GC-MS method.

EFFECTS OF CHEMICAL DISPERSANT ON OIL SEDIMENTATION DUE TO OIL-SPM FLOCCULATION: EXPERIMENTS WITH THE NIST STANDARD REFERENCE MATERIAL 1941?

ABSTRACT As it is well established that application of chemical dispersant to oil slicks enhances the concentration of oil droplets and reduces their size, chemical dispersants are expected to enha...

Aromatic Steroids in Crude Oils and Petroleum Products and Their Applications in Forensic Oil Spill Identification

Aromatic steroids including monoaromatic (MAS) and triaromatic steroids (TAS) are a series of naphthenoaromatic hydrocarbons, which consist of mixed structures of aromatic and saturated 6-carbon or 5-carbon rings. Although these aromatic steroids are in relatively low concentration in oils, their specific fingerprints and high weathering resistance make them desirable biomarkers for the characterization, correlation, differentiation, and source identification in environmental forensic investigations of oil spills. This study presents a quantitative GC/MS analysis of these aromatic hydrocarbons in a number of crude oils and refined petroleum products including light and mid-range distillate fuels, heavy fuels, and lubricating oils collected from various sources. TAS-cholestanes (C26), TAS-ergostanes (C27), and TAS-stigmastanes (C28) are the most distinguishable triaromatic steroids in most oil samples. C26 TAS-cholestane (20R) and C27 TAS-ergostane (20S) are coeluted and often present as the highest peak in m/z 231 chromatograms. A cluster of aromatic steroids were determined in nearly all the studied crude oils at various concentrations. These compounds are generally not detected in light fuel oil like gasoline and light diesel, but at variable abundance in heavy fuels and lubricating oils. In order to better understand the occurrence of aromatic steroids in refined petroleum products, a crude oil was compared with its products of laboratory fluid catalytic cracking (FCC) and hydrotreating processes. The effects of evaporative weathering and biodegradation on these compounds were evaluated with suites of weathered oil samples.