Full-scale bioremediation of diesel-polluted soil in an Arctic landfarm.

A full-scale, experimental landfarm was tested for the capacity to biodegrade oil-polluted soil under high-Arctic tundra conditions in northeast Greenland at the military outpost 9117 Station Mestersvig. Soil contaminated with Arctic diesel was transferred to the landfarm in August 2012 followed by yearly addition of fertilizer and plowing and irrigation to optimize microbial diesel biodegradation. Biodegradation was determined from changes in total petroleum hydrocarbons (TPH), enumeration of specific subpopulations of oil-degrading microorganisms (MPN), and changes in selected classes of alkylated isomers and isomer ratios. Sixty-four percent of the diesel was removed in the landfarm within the first year, but a recalcitrant fraction (18%) remained after five years. n-alkanes and naphthalenes were biodegraded as demonstrated by changing isomer ratios. Dibenzothiophenes and phenanthrenes showed almost constant isomer ratios indicating that their removal was mostly abiotic. Oil-degrading microorganisms were present for the major components of diesel (n-alkanes, alkylbenzenes and alkylnaphthalenes). The degraders showed very large population increases in the landfarm with a peak population of 1.2 × 109 cells g-1 of total diesel degraders. Some diesel compounds such as cycloalkanes, hydroxy-PAHs and sulfur-heterocycles had very few or no specific degraders, these compounds may consequently be degraded only by slow co-metabolic processes or not at all.

Supercritical fluid chromatography for the analysis of oxygenated polycyclic aromatic compounds in unconventional oils.

Unconventional oil feeds can be rich in oxygenated organic compounds that will negatively affect the fuel properties if they are not removed during refining. In this study, supercritical fluid chromatography (SFC) was utilised for the combined analysis of polycyclic aromatic hydrocarbons (PAHs) and oxygenated polycyclic aromatic compounds (OPACs). One objective was to chromatographically separate PAHs from OPACs; another to reach a high peak capacity, improved peak shapes and high signal-to-noise ratios (S/N) for OPACs. These objectives were set to establish a non-target analysis method for oxygenated compounds in unconventional oils by SFC hyphenated to a UV detector and a quadrupole time-of-flight mass spectrometer (QTOF-MS) with negative electrospray ionisation (ESI-). Highest peak capacities were observed with a 2-picolylamine column with methanol as modifier, however, a better resolution and S/N were obtained with ethanol and 0.1% formic acid. The elution order for OPACs on all columns followed mainly the polarity of the analytes: furans < aldehydes ≤ ketones < phenols ≤ carboxylic acids. Best separation between PAHs and OPACs was achieved with the ethylene-bridged silica column. The optimised SFC-UV-ESI--QTOF-MS method was tested on a coal tar middle distillate and a pyrolysis oil where a number of homologous series (e.g. hydroxy-naphthalenes and -benzaldehydes) was tentatively identified.

In situ biodegradation, photooxidation and dissolution of petroleum compounds in Arctic seawater and sea ice.

In pristine sea ice-covered Arctic waters the potential of natural attenuation of oil spills has yet to be uncovered, but increasing shipping and oil exploitation may bring along unprecedented risks of oil spills. We deployed adsorbents coated with thin oil films for up to 2.5 month in ice-covered seawater and sea ice in Godthaab Fjord, SW Greenland, to simulate and investigate in situ biodegradation and photooxidation of dispersed oil. GC-MS-based chemometric methods for oil fingerprinting were used to identify characteristic signatures for dissolution, biodegradation and photooxidation. In sub-zero temperature seawater, fast degradation of n-alkanes was observed with estimated half-life times of ∼7 days. PCR amplicon sequencing and qPCR quantification of bacterial genes showed that a biofilm with a diverse microbial community colonised the oil films, yet a population related to the psychrophilic hydrocarbonoclastic gammaproteobacterium Oleispira antarctica seemed to play a key role in n-alkane degradation. Although Oleispira populations were also present in sea ice, we found that biofilms in sea ice had 25 to 100 times lower bacterial densities than in seawater, which explained the non-detectable n-alkane degradation in sea ice. Fingerprinting revealed that photooxidation, but not biodegradation, transformed polycyclic aromatic compounds through 50 cm-thick sea ice and in the upper water column with removal rates up to ∼1% per day. Overall, our results showed a fast biodegradation of n-alkanes in sea ice-covered seawater, but suggested that oils spills will expose the Arctic ecosystem to bio-recalcitrant PACs over prolonged periods of time.

Polycyclic Aromatic Acids Are Primary Metabolites of Alkyl-PAHs-A Case Study with Nereis diversicolor.

Although concentrations of alkylated polycyclic aromatic hydrocarbons (alkyl-PAHs) in oil-contaminated sediments are higher than those of unsubstituted PAHs, only little attention has been given to metabolism and ecotoxicity of alkyl-PAHs. In this study we demonstrated that metabolism of alkyl-PAHs primarily forms polycyclic aromatic acids (PAAs). We generalize this to other alkyl-PAHs, based on literature and the present study of the metabolism of 1-methylphenanthrene, 3,6-dimethylphenanthrene, and 1-, 2-, 3-, and 6-methylchrysene related to their unsubstituted parent PAHs. Also, we observed that body burdens and production of PAAs was related to the position of the methyl group, showing the same isomer specific preferences as for microbial degradation of alkyl-PAHs. We detected a high production of PAAs, and larger metabolism of alkyl-PAHs than their unsubstituted parent PAHs. We therefore propose that carboxylic acid metabolites of alkyl-PAHs have the potential of constituting a new class of contaminants in marine waters that needs attention in relation to ecological risk assessments.

Effects of Nereis diversicolor on the transformation of 1-methylpyrene and pyrene: transformation efficiency and identification of phase I and II products.

Transformation of nonsubstituted and alkyl-substituted polycyclic aromatic hydrocarbons (PAHs) by the benthic invertebrate Nereis diversicolor was compared in this study. Pyrene and 1-methylpyrene were used as model compounds for nonsubstituted and alkyl-substituted PAHs, respectively. Qualitative and quantitative analyses of metabolites and parent compounds in worm tissue, water, and sediment were performed. Transformation of 1-methylpyrene generated the benzylic hydroxylated phase I product, 1-pyrenecarboxylic acid that comprised 90% of the total metabolites of 1-methylpyrene, and was mainly found in water extracts. We tentatively identified 1-methylpyrene glucuronides and 1-carbonylpyrene glycine as phase II metabolites not previously reported in literature. Pyrene was biotransformed to 1-hydroxypyrene, pyrene-1-sulfate, pyrene-1-glucuronide, and pyrene glucoside sulfate, with pyrene-1-glucuronide as the most prominent metabolite. Transformation of 1-methylpyrene (21% transformed) was more than 3 times as efficient as pyrene transformation (5.6% transformed). Because crude oils contain larger amounts of C1-C4-substituted PAHs than nonsubstituted PAHs, the rapid and efficient transformation of sediment-associated 1-methylpyrene may result in a high exposure of water-living organisms to metabolites of alkyl-substituted PAHs, whose toxicities are unknown. This study demonstrates the need to consider fate and effects of substituted PAHs and their metabolites in risk assessments.

Assessment of oil weathering by gas chromatography-mass spectrometry, time warping and principal component analysis.

Detailed characterization and understanding of oil weathering at the molecular level is an essential part of tiered approaches for forensic oil spill identification, for risk assessment of terrestrial and marine oil spills, and for evaluating effects of bioremediation initiatives. Here, a chemometric-based method is applied to data from two in vitro experiments in order to distinguish the effects of evaporation and dissolution processes on oil composition. The potential of the method for obtaining detailed chemical information of the effects from evaporation and dissolution processes, to determine weathering state and to distinguish between various weathering processes is investigated and discussed. The method is based on comprehensive and objective chromatographic data processing followed by principal component analysis (PCA) of concatenated sections of gas chromatography-mass spectrometry chromatograms containing homologue series of n-alkanes (m/z 85) and alkyltoluenes (m/z 105). The PCA model based solely on in vitro samples and validated by samples from an authentic marine oil spill gives a detailed description of the temporal changes in n-alkane and alkyltoluene compositions. The PCA model is able to distinguish the two physical weathering processes both with respect to removal rate and relative changes. The model shows that evaporation has a large impact on both the alkyltoluenes and on the n-alkanes (e.g., nC-18 is completely removed after 192 days of in vitro evaporation). Dissolution, however, is shown to be a much slower process for weathering of heavy fuel oils with only limited impact on the alkyltoluenes, and no effects on the n-alkane distribution.