Recommendations for the advancement of oil-in-water media and source oil characterization in aquatic toxicity test studies

During toxicity testing, chemical analyses of oil and exposure media samples are needed to allow comparison of results between different tests as well as to assist with identification of the drivers and mechanisms for the toxic effects observed. However, to maximize the ability to compare results between different laboratories and biota, it has long been recognized that guidelines for standard protocols were needed. In 2005, the Chemical Response to Oil Spills: Ecological Effects Research Forum (CROSERF) protocol was developed with existing common analytical methods that described a standard method for reproducible preparation of exposure media as well as recommended specific analytical methods and analyte lists for comparative toxicity testing. At the time, the primary purpose for the data collected was to inform oil spill response and contingency planning. Since then, with improvements in both analytical equipment and methods, the use of toxicity data has expanded to include their integration into fate and effect models that aim to extend the applicability of lab-based study results to make predictions for field system-level impacts. This paper focuses on providing a summary of current chemical analyses for characterization of oil and exposure media used during aquatic toxicity testing and makes recommendations for the minimum analyses needed to allow for interpretation and modeling purposes.publishedVersio

Use of a Novel Fluorinated Organosulfur Compound To Isolate Bacteria Capable of Carbon-Sulfur Bond Cleavage

The vacuum residue fraction of heavy crudes contributes to the viscosity of these oils. Specific microbial cleavage of C—S bonds in alkylsulfide bridges that form linkages in this fraction may result in dramatic viscosity reduction. To date, no bacterial strains have been shown conclusively to cleave C—S bonds within alkyl chains. Screening for microbes that can perform this activity was greatly facilitated by the use of a newly synthesized compound, bis-(3-pentafluorophenylpropyl)-sulfide (PFPS), as a novel sulfur source. The terminal pentafluorinated aromatic rings of PFPS preclude growth of aromatic ring-degrading bacteria but allow for selective enrichment of strains capable of cleaving C—S bonds. A unique bacterial strain, Rhodococcus sp. strain JVH1, that used PFPS as a sole sulfur source was isolated from an oil-contaminated environment. Gas chromatography-mass spectrometry analysis revealed that JVH1 oxidized PFPS to a sulfoxide and then a sulfone prior to cleaving the C—S bond to form an alcohol and, presumably, a sulfinate from which sulfur could be extracted for growth. Four known dibenzothiophene-desulfurizing strains, including Rhodococcus sp. strain IGTS8, were all unable to cleave the C—S bond in PFPS but could oxidize PFPS to the sulfone via the sulfoxide. Conversely, JVH1 was unable to oxidize dibenzothiophene but was able to use a variety of alkyl sulfides, in addition to PFPS, as sole sulfur sources. Overall, PFPS is an excellent tool for isolating bacteria capable of cleaving subterminal C—S bonds within alkyl chains. The type of desulfurization displayed by JVH1 differs significantly from previously described reaction results

Dibenzyl Sulfide Metabolism by White Rot Fungi

Microbial metabolism of organosulfur compounds is of interest in the petroleum industry for in-field viscosity reduction and desulfurization. Here, dibenzyl sulfide (DBS) metabolism in white rot fungi was studied. Trametes trogii UAMH 8156, Trametes hirsuta UAMH 8165, Phanerochaete chrysosporium ATCC 24725, Trametes versicolor IFO 30340 (formerly Coriolus sp.), and Tyromyces palustris IFO 30339 all oxidized DBS to dibenzyl sulfoxide prior to oxidation to dibenzyl sulfone. The cytochrome P-450 inhibitor 1-aminobenzotriazole eliminated dibenzyl sulfoxide oxidation. Laccase activity (0.15 U/ml) was detected in the Trametes cultures, and concentrated culture supernatant and pure laccase catalyzed DBS oxidation to dibenzyl sulfoxide more efficiently in the presence of 2,2′-azinobis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) than in its absence. These data suggest that the first oxidation step is catalyzed by extracellular enzymes but that subsequent metabolism is cytochrome P-450 mediated

Hydrogenation of Olefins in Bitumen-Derived Naphtha over a Commercial Hydrotreating Catalyst

Instability associated with the presence of olefins in bitumen that is thermally processed during partial upgrading is a major concern for pipeline transportation and downstream refining. A common strategy for stabilizing thermally processed oils is to selectively hydrogenate the olefin-rich fractions, typically, the naphtha fraction (IBP–204 °C). In this paper, olefin hydrogenation was studied with hydrotreated bitumen-derived naphtha spiked with five model olefin compounds under mild hydrotreating conditions. The hydrogenation reactivities of the five model olefin/diolefin compounds are ranked in the order 1,3-hexadiene > allylbenzene > 1-heptene > 2-methyl-2-pentene > 1-methyl-cyclopentene. The reactivity is largely determined by the position of the double bond, and, to a lesser extent, by the molecular structure of the olefin. The conjugated diolefin, 1,3-hexadiene, was the most reactive. The two terminal olefins, 1-heptene and allylbenzene, were observed to be more reactive than the two olefins with internal double bonds: 2-methyl-2-pentene and 1-methyl-cyclopentene. Results also show that temperature has a significant effect on olefin hydrogenation performance, with the pressure and the liquid hourly space velocity having relatively moderate effects. Meanwhile, flash calculations confirmed the presence of vapor–liquid equilibrium under the operation conditions used. When the reactor temperature is 150 °C or less, reactions primarily occur in the liquid phase, whereas at temperatures of 200 °C or higher, the reactions occur in the vapor phase. A hydrogenation kinetics model is proposed that successfully describes the observed trends of olefin hydrogenation in the liquid phase

DataSheet1_Diluted bitumen weathered under warm or cold temperatures is equally toxic to freshwater fish.docx

Canada is one of the main petroleum producers in the world. Through its oil sands exploitation, a viscous bitumen mixed with sand, water, and clay is being produced. This bitumen is so viscous that approximatively 20%–30% of diluent needs to be added to ease transportation, resulting in a mixture called diluted bitumen (dilbit). The transport of dilbit through North America comes with a potential risk for oil spills in freshwater ecosystems at any time of the year. In this study, a mesoscale spill tank was used to study dilbit spills in freshwater to understand the effect of cold (winter-like) vs. warmer (spring- and fall-like) water temperatures on its natural weathering and their toxicity to fathead minnow (Pimephales promelas) embryos. Water samples were collected weekly during two consecutive 35-day experiments ran at either 2 or 15 °C. Each week, fish larvae were exposed for 7 days, and water analysis was performed. Chemical analysis showed that the volatile organic compound, total organic carbon, and polycyclic aromatic hydrocarbon concentrations decreased in both experiments with time, while fish larvae exposed to both temperature settings yielded increased abnormalities, EROD activity, CYP1A, and glutathione S-transferase mRNA expression levels, and decreased heart rate. Importantly, there were no major differences between the temperature regimes on dilbit weathering, highlighting that if a spill occurs in colder waters, it would be equally toxic to organisms. This work provides new data on the potential risk of oil spill for use during response planning and modelling.</p

Waxy Gels with Asphaltenes 2: Use of Wax Control Polymers

The effect of asphaltenes on the effectiveness of wax control polymers was studied using a model waxy oil and a set of polymers with controlled crystalline and polar/aromatic content. The effect of crystalline content was examined with a set of maleic anhydride copolymers with alkyl appendages of different lengths. Different polar and/or aromatic functionalities were incorporated into the maleic anhydride copolymers (MAC) and poly(ethylene butene) polymers to probe potential interactions with the asphaltenes. The performance of the polymers was measured by testing their effect upon precipitation temperature, gelation temperature, and yield stress. Some polymers provided little or no benefit. Others had significant effects, reducing precipitation temperatures up to 1.9 °C, gelation temperatures up to 37 °C, and yield stresses up to 2200-fold for solutions of 8 wt % wax. Polymer efficacy was almost entirely determined by the crystalline functionality incorporated into the polymer rather than the presence of polar functionality designed to target interactions with the asphaltenes. The performance of the polymers is attributed to the ability of the polymers to coprecipitate with the wax. Comparison with previously published results using the same wax showed that the selectivity of the MACs was strongly affected by wax concentration, not because the quantity of wax overwhelmed the polymer, but because the range of wax precipitation temperatures increased above that of the polymer. Comparison of the effect of polymers in solutions with and without asphaltenes showed that asphaltenes had different effects on polymer performance, depending on the property being measured (precipitation temperature, gelation temperature, or yield stress)

Correction to Diesel Surrogate Fuels for Engine Testing and Chemical-Kinetic Modeling: Compositions and Properties

Correction to Diesel Surrogate Fuels for Engine Testing and Chemical-Kinetic Modeling: Compositions and Propertie