Continuous open flow-through system as a model for oil degradation in the arctic ocean

A continuous flow-through system incubated in situ was used to model oil biodegradation in Arctic coastal waters. High numbers of oil-degrading microorganisms were found in the Arctic coastal waters examined in this study. The microbial community underlying oil slicks increased and showed a population shift to a greater percentage of hydrocarbon-utilizing microorganisms. Microbial populations and oil biodegradation were increased by the addition of nitrogen and phosphorus. Both abiotic and biodegradative losses were lower than expected, perhaps due to the unusually harsh, ice-dominated Arctic summer, during which these tests were conducted. Chromatographic and spectrometric analyses showed that residual oils contained similar percentages of individual components and classes of hydrocarbons, regardless of the amount of degradation, indicating that most components of the oil were being degraded at similar rates.     

Microbial degradation of four Nigerian crude oils in an estuarine microcosm

Four Nigerian crude oils (Bonny Light, Bonny Medium, Escravos Light and Forcados Blend) that differ substantially in fractional composition were exposed to the Lagos Lagoon waters in microcosm experiments with oil-impregnated membrane filters. Changes in microbial numbers on the membranes and in the residual oil concentration showed a relationship between the fractional composition and the biodegradation rates of the oils, with the lighter oils disappearing more rapidly. After 10 weeks exposure in the lagoon, only 15% (w/w) of the Bonny Light crude remained on the filters as compared with 20, 32 and 45% (w/w) for Escravos Light, Bonny Medium and Forcados Blend respectively. The hydrocarbon-utilizing microbial colonizers of the oil-impregnated membranes were Micrococcus, Bacillus, Pseudomonas, Flavobacterium, Alcaligenes and Aspergillus niger.     

Response of Antarctic Soil Bacterial Assemblages to Contamination by Diesel Fuel and Crude Oil

Abstract The effects of diesel fuel and ``Arabian light' crude oil addition on Antarctic bacterial assemblages were studied in four contaminated soils during 1 year in the Terre Adelie land area. Monthly sampling allowed a regular survey of the bacterial changes occurring in the contaminated soils. All samples were analyzed for total bacteria, heterotrophic culturable microbiota, and hydrocarbon-utilizing microbiota. Crude oil contamination induced an initial increase of all bacterial parameters in all contaminated soils. Diesel oil contamination had a more complex effect. Hydrocarbon degrading bacterial abundance increases occurred after diesel oil addition. In contrast, general heterotrophic bacterial abundance could significantly decrease in the same conditions. In all cases the stimulatory effects of oil addition disappeared after several months of contamination. Received: 13 April 1999; Accepted: 24 February 2000; Online Publication: 29 May 2000     

Microbial degradation of hydrocarbons in the environment.

The ecology of hydrocarbon degradation by microbial populations in the natural environment is reviewed, emphasizing the physical, chemical, and biological factors that contribute to the biodegradation of petroleum and individual hydrocarbons. Rates of biodegradation depend greatly on the composition, state, and concentration of the oil or hydrocarbons, with dispersion and emulsification enhancing rates in aquatic systems and absorption by soil particulates being the key feature of terrestrial ecosystems. Temperature and oxygen and nutrient concentrations are important variables in both types of environments. Salinity and pressure may also affect biodegradation rates in some aquatic environments, and moisture and pH may limit biodegradation in soils. Hydrocarbons are degraded primarily by bacteria and fungi. Adaptation by prior exposure of microbial communities to hydrocarbons increases hydrocarbon degradation rates. Adaptation is brought about by selective enrichment of hydrocarbon-utilizing microorganisms and amplification of the pool of hydrocarbon-catabolizing genes. The latter phenomenon can now be monitored through the use of DNA probes. Increases in plasmid frequency may also be associated with genetic adaptation. Seeding to accelerate rates of biodegradation has been shown to be effective in some cases, particularly when used under controlled conditions, such as in fermentors or chemostats.     

Effectiveness of bioremediation of crude oil contaminated subantarctic intertidal sediment: the microbial response

A field study was initiated in February 1996 in a remote sandy beach of The Grande Terre (Kerguelen Archipelago, 69° 42° E, 49° 19° S) with the objective of determining the long-term effects of some bioremediation agents on the biodegradation rate and the toxicity of oil residues under severe subantarctic conditions. A series of 10 experimental plots were settled firmly into sediment. Each plot received 2L of Arabian light crude oil and some of them were treated with bioremediation agents: slow release fertilizer Inipol EAP-22 (Elf Atochem) or fish composts. Plots were sampled on a regular basis over a 3-year period. A two-order of magnitude increase of saprophytic and hydrocarbon-utilizing microorganisms occurred during the first month of the experiment in all treated enclosures, but no clear differences appeared between the plots. Very high microbial populations were present during the experiment. Biodegradation within treated spots was faster than within the untreated ones and appeared almost complete after 6 months as indicated by the degradation index of aliphatic hydrocarbons within all plots. The analysis of interstitial water collected below the oily residues presented no toxicity. However, a high toxicity signal, using Microtox solid phase, appeared for all oiled sand samples with a noticeable reduction with time even if the toxicity signal remained present and strong after 311 days of oil exposition. As a conclusion, it is clear that the microbial response was rapid and efficient in spite of the severe weather conditions, and the rate of degradation was improved in presence of bioremediation agents. However, the remaining residues had a relatively high toxicity.     

Incomplete Hydrocarbon Biodegradation in Contaminated Soils: Limitations in Bioavailability or Inherent Recalcitrance?

Bioremediation has been used to treat soils contaminated with complex mixtures of organic compounds such as total petroleum hydrocarbons (TPH), oil and grease (O&G), or polycyclic aromatic hydrocarbons (PAHs). Despite the common use and cost-effectiveness of bioremediation for treating hydrocarbon-contaminated soils, it has been observed that a residual fraction remains undegraded in the soil even when optimal biodegradation conditions have been provided. This paper provides a brief review of the two major conceptual models that have been used to explain why a residual hydrocarbon fraction remains in the soil after bioremediation treatment. The contaminant sequestration model is based on the assumption that a certain fraction of hydrocarbons is “locked up” in small soil pores within soil particles or aggregates. These sorbed hydrocarbons are believed to be inaccessible to soil microorganisms. Consequently, limitations in bioavailability are thought to be the major reason for incomplete hydrocarbon biodegradation, particularly in aged or weathered soils. Alternatively, according to the inherent recalcitrance model, incomplete TPH biodegradation may be caused by the presence of certain hydrocarbons that are inherently recalcitrant to biodegradation or are only extremely slowly degradable even under optimal conditions. Each conceptual model provides different explanations regarding the potential risks of the residual hydrocarbon fraction. If the residual TPH is truly sequestered within the soil pore space, it is unlikely that these compounds will pose any significant risk to human or environmental receptors. By contrast, these risks may be considerably greater if the residual TPH fraction consists of inherently recalcitrant compounds that reside mostly on the surface of soil particles and therefore are much more available to potential receptors. Both conceptual models and their implications for the potential risk of the residual TPH fraction are discussed.     

Hydrocarbon-degrading filamentous fungi isolated from flare pit soils in northern and western Canada

Sixty-four species of filamentous fungi from five flare pits in northern and western Canada were tested for their ability to degrade crude oil using gas chromatographic analysis of residual hydrocarbons following incubation. Nine isolates were tested further using radiorespirometry to determine the extent of mineralization of model radiolabelled aliphatic and aromatic hydrocarbons dissolved in crude oil. Hydrocarbon biodegradation capability was observed in species representing six orders of the Ascomycota. Gas chromatography indicated that species capable of hydrocarbon degradation attacked compounds within the aliphatic fraction of crude oil, n-C12-n-C26; degradation of compounds within the aromatic fraction was not observed. Radiorespirometry, using n-[1-14C]hexadecane and [9-14C]phenanthrene, confirmed the gas chromatographic results and verified that aliphatic compounds were being mineralized, not simply transformed to intermediate metabolites. This study shows that filamentous fungi may play an integral role in the in situ biodegradation of aliphatic pollutants in flare pit soils.     

Changes in the biofilm microflora of limestone caused by atmospheric pollutants

Historic limestone materials in urban environments are continually exposed to air pollutants, including sulfur compounds and hydrocarbons. We investigated the effects of air pollution on the biofilm microflora of historic limestone gravestones located at two locations Massachusetts, USA. Our data showed that the culturable populations of chemolithotrophic and heterotrophic bacteria, and fungi were suppressed in the polluted habitat comparing with the unpolluted location. The diversity of the microflora was also reduced in the surface biofilms on gravestones in the city contaminated by air pollution. However, both the sulfur-oxidizing and hydrocarbon-utilizing microflora were enriched in the biofilms exposed to air pollution. In a laboratory study, low concentrations of the polluting chemicals stimulated growth of these bacteria, and resulted in rapid acid production. Scanning electron microscopy demonstrated that the biofilms of both the sulfur-oxidizing bacteria and the hydrocarbon-degrading microflora penetrated into the limestone. The enrichment of sulfur- and hydrocarbon-utilizing bacteria in the biofilms may contribute to dissolution of the stone. However, further research is required to determine the effects of specific metabolites of these microorganisms on stone deterioration.     

Effect of growing region on quality characteristics and phenolic compounds of chemlali extra-virgin olive oils

The present work aims at the characterizing chemlali extra-virgin olive oils from different locations in northern, central and southern Tunisia in terms of their quality indices, fatty acids, sterol content, phenolic composition and sensory profiles to show the classification of oil samples according to the geographical area. The majority of the analytical parameters have presented statistically significant differences (p < 0.05). The main sterols found in all chemlali olive oils were β-sitosterol, ?-5-avenasterol, campesterol and stigmasterol. The phenolic compounds present in five olive oil samples were analysed by high-performance liquid chromatography (HPLC) method, thus identifying 16 phenolic compounds belonging to different phenolic types. The results have shown no qualitative differences in the phenolic fractions among extra-virgin olive oils from different geographical regions. However, the quantitative differences were observed in a wide number of phenolic compounds. In all studied olive oil samples, secoiridoids were the most abundant, followed by lignans, phenolic alcohols and flavonoids, respectively. Although there is no significant influence on the sensory scores of oils, some slight changes in sensorial profiles were noted: slightly higher intensities of sensory characteristics that are pungent, fruity and bitter in chemlali olive oil from Hammamet and Gafsa.     

Microbial Factors Rather Than Bioavailability Limit the Rate and Extent of PAH Biodegradation in Aged Crude Oil Contaminated Model Soils

The rate and extent of polynuclear aromatic hydrocarbons (PAH) biodegradation in a set of aged model soils that had been contaminated with crude oil at the high concentrations (i.e.,>20,000?mg/kg) normally found in the environment were measured in 90-week slurry bioremediation experiments. Soil properties such as organic matter content, mineral type, particle diameter, surface area, and porosity did not significantly influence the PAH biodegradation kinetics among the 10 different model soils. A comparison of aged and freshly spiked soils indicates that aging affects the biodegradation rate and extent only for higher-molecular-weight PAHs, while the effects of aging are insignificant for 4-ring PAHs and total PAHs. In all model soils with the exception of kaolinite clay, the rate of abiotic desorption was faster than the rate of biodegradation during the initial phase of bioremediation treatment, indicating that PAH biodegradation was limited by microbial factors. Similarly, any of the higher-molecular-weight PAHs that were still present after 90 weeks of treatment were released rapidly during abiotic desorption tests, which demonstrates that bioavailability limitations were not responsible for the recalcitrance of these hydrocarbons. Indeed, an analysis of microbial counts indicates that a severe reduction in hydrocarbon degrader populations may be responsible for the observed incomplete PAH biodegradation. Therefore, it can be concluded that the recalcitrance of PAHs during bioremediation is not necessarily due to bioavailability limitations and that these residual contaminants therefore might pose a greater risk to environmental receptors than previously thought.     

Vanadium as a tracer of oil pollution in the sediments of Kuwait

Vanadium is important as an indicator of oil pollution since oil is one of the main contributors of vanadium to the environment and because most crude oils contain relatively high concentrations of vanadium (30.6 ± 14.3 mg kg^–1 were measured in nine different Kuwait crudes). If oil has settled to the bottom and biodegradation has taken place, it is obvious that enrichment of vanadium in the sediment may be observed.More than 200 sampling sites were selected in the coastal zone of Kuwait and sediment samples were analyzed for grain size distribution, CaC0₃ content, heavy metals and TOC. The analytical results were normalized by taking into account the natural background levels of vanadium in different sediment fractions.After evaluation of the results, vanadium enrichments of as much as 10 to 77 mg kg^–1 were found at 15 sampling locations and of 1 to 10 mg kg^–1 at many others. The areas of vanadium enrichment in the sediments were located 3–5 km from the shoreline in the areas of wastewater discharges, near oil loading piers and in the shipping channels. There was no correlation between vanadium and TOC indicating that biodegradation of oils had taken place. However, high TOC values in the sediments were determined in the near shore sediments around the outlets.     

Applied models to biodegradation kinetics of lubricant and vegetable oils in wastewater

Bioremediation technologies are used in order to remove pollutants from the environment in a safe, economical and harmless way during the treatment of waste, especially with the use of techniques such as biodegradation. A lubricant and vegetable oil contaminated water sample was studied in order to evaluate the biodegradability of different types of oils, considering the relevance of the obtained data in the bioremediation procedures. The objective of this paper is to use respirometry technique as a biodegradation process data source, and then apply to the obtained data the experimental design of mathematical models to characterize and determinate how the different types of oils are capable of affecting the parameters in biodegradation kinetics. The kinetics was then evaluated through selected models with a reasonable fit to experimental data. The Bartha and Pramer respirometer is used as a method to accurately measure the CO₂ formation in the organic compounds degradation by microorganisms. Therefore, the difference in biodegradation efficiency process is compared in the different groups of oils using mathematical models fitting the obtained data for the kinetics of biodegradation. The results demonstrated that used lubricant automotive oils are more susceptible to the biodegradation process, since their molecular structures had already been altered after use. In general, automotive lubricant oils shown better performance in biodegradation than vegetable oils. The models proposed for the obtained data in each of these assays demonstrated that vegetable oils biodegradation rate tends to decrease faster and end sooner than the automotive oils. Also, the modeling predicted that higher rates of biodegradation and total CO₂ production are to be expected in automotive lubricant oils rather than vegetable oils.     

Effects of sodium chloride on biodegradation of crude oils by two species ofAeromonas

Summary The biodegradation of five weathered crude oils by two species ofAeromonas, (B59-4 and E. BOB) was investigated in varying concentrations of sodium chloride. A minimal salts medium whose NaCl concentration increased serially by 0.5% w/v up to 1.5% w/v was used to investigate the growth of these strains in glucose, and their biodegradation of the crude oils. The latter was also investigated in fresh and aged sea water. Strain B59-4 was more potent than E. BOB in the degradation of all five crude oils and at all four levels of salt concentration tested. The amount of oil degraded by each strain increased initially to a maximum level at 0.5% w/v NaCl, but thereafter decreased with increasing salt concentration, and the patterns were similar to those of aged and fresh sea water, respectively. The Forties and Nigerian crude oils with lower specific gravity, were more readily degraded than the Libyan and Venezuelan with higher specific gravity. The growth of the two strains ofAeromonas in glucose and their biodegradation of crude oils was optimal at 0.5% w/v NaCl, and thereafter decreased with increasing salt concentration of the basal medium.     

Viscosity properties of mineral paraffinic base oils as a key factor in their primary biodegradability

The primary biodegradability of two types of paraffinic base oils (solvent and catalytically dewaxed oils) and their blends was evaluated using the CEC L-33-A-93 test. The biodegradability values varied between 10% and 75%. Base oil mixtures displayed varying contents in aromatic and polar compounds and a wide range of kinematic viscosity (KV) values, from roughly 10 to 600 cSt (at 40°C), while their viscosity indices were almost constant (90-100). The biodegradability of oils was closely related to their content in polycyclic aromatic hydrocarbons and was also decreasing with kinematic viscosity. For the two types of base oils, a linear relationship could be set between the biodegradation percentages and the logarithms of KV values. These results show that, beside overall chemical features such as the contents in aromatic compounds, KV may be a prominent parameter for assessing the primary biodegradability of mineral base oils.     

Bioremediation and Biorestoration of a Crube Oil-Contaminated Freshwater Wetland on the St.Lawrence River

Biostimulation by nutrient enrichment and phytoremediation were studied for the restoration of an acutely stressed freshwater wetland experimentally exposed to crude oil. The research was carried out along the shores of the St. Lawarence River at Ste. Croix, Quebec, Canada. The research determined the effectiveness of fertilizer addition in enhancing the biodegradation rates of residual oil. It further examined the rate at which the stressed ecosystem recovered with and without the addition of inorganic fertilizers and the role of nutrients in enhancing wetland restoration in the absence of healthy wetland plants. Chemical analysis of integrated sediment core samples to the depth of oil penetration within the experimental plots indicated that addition of inorganic nutrients did not enhance the disappearance of alkanes or PAHs. In surface samples, however, hydrocarbon disappearance rates were higher when the metabolic activity of wetland plants was suppressed by the removal of emergent plant growth. These results suggest that oxygen limitation plays a major role in preventing rapid biodegradation of hydrocarbons in anoxic wetland sediment.     

Effects of Temperature and Crude Oil Composition on Petroleum Biodegradation

The biodegradability of seven different crude oils was found to be highly dependent on their composition and on incubation temperature. At 20 C lighter oils had greater abiotic losses and were more susceptible to biodegradation than heavier oils. These light crude oils, however, possessed toxic volatile components which evaporated only slowly and inhibited microbial degradation of these oils at 10 C. No volatile toxic fraction was associated with the heavier oils tested. Rates of oil mineralization for the heavier oils were significantly lower at 20 C than for the lighter ones. Similar relative degradation rates were found with a mixed microbial community, using CO2 evolution as the measure, and with a Pseudomonas isolate from the Arctic, using O2 consumption as the measure. The paraffinic, aromatic, and asphaltic fractions were subject to biodegradation. Some preference was shown for paraffin degradation, especially at low temperatures. Branched paraffins, such as pristane, were degraded at both 10 and 20 C. At best, a 20% residue still remained after 42 days of incubation. Oil residues generally had a lower relative percentage of paraffins and higher percentage of asphaltics than fresh or weathered oil.     

Microbial populations and hydrocarbon biodegradation potentials in fertilized shoreline sediments affected by the T/V Exxon Valdez oil spill.

The effort of clean up the T/V Exxon Valdez oil spill in Prince William Sound, Alaska, included the use of fertilizers to accelerate natural microbial degradation of stranded oil. A program to monitor various environmental parameters associated with this technique took place during the summer of 1990. Microbiological assays for numbers of heterotrophic and oil-degrading microbes and their hydrocarbon mineralization potentials were performed in support of this program. Fertilizer addition resulted in higher hexadecane and phenanthrene mineralization potentials on treated plots than on untreated reference plots. Microbial numbers in treated and reference surface sediments were not significantly different immediately after the first nutrient application in May 1990. However, subsurface sediments from treated plots had higher numbers of hydrocarbon degraders than did reference sediments shortly after treatment. The second application of fertilizer, later in summer, resulted in surface and subsurface increases in numbers of hydrocarbon degraders with respect to reference sediments at two of the three study sites. Elevated mineralization potentials, coupled with increased numbers of hydrocarbon degraders, indicated that natural hydrocarbon biodegradation was enhanced. However, these microbiological measurements alone are not sufficient to determine in situ rates of crude oil biodegradation.     

Biostimulation of Natural Microbial Assemblages in Oil-Amended Vegetated and Desert Sub-Antarctic Soils

A field study was initiated in December 2000 in two selected soils of The Grande Terre (Kerguelen Archipelago) with the objective of determining the long-term effects of fertilizer addition on the biodegradation rate and the toxicity of oil residues under severe sub-Antarctic conditions. Two soils were selected. The first site supports an abundant vegetal cover; the second one was desert soil, devoid of plant material. These two soils were located in the vicinity of the permanent station of Port-aux-Français (69° 42E; 49° 19S). A series of five experimental plots (0.75 × 0.75 m) were settled firmly into each of the studied soils. Each plot received 500 mL of diesel or Arabian light crude oil, and some of them were treated with a bioremediation agent: slow-release fertilizer Inipol EAP-22 (Elf Atochem). All the plots were sampled on a regular basis over a 1 year period. Heterotrophic and hydrocarbon-degrading microorganisms increased by two orders of magnitude during the first month of the experimentation in all treated enclosures, but differences appeared between the different plots. The microbial response was improved by bioremediation treatments. However, fertilizer addition had a greater impact on the desert soil when compared to the vegetated one. All chemical indices show a reduction of alkanes and light aromatics. Toxicity results show a high variability between treatments and environmental conditions. As a conclusion, it is clear that the microbial response was rapid and efficient in spite of the severe weather conditions, and the rate of degradation was improved by bioremediation treatments. However, after 1 year of treatment, the signal of a relatively high toxicity of oiled residues remained present in the two studied soils.     

Microbial populations and hydrocarbon biodegradation potentials in fertilized shoreline sediments affected by the T/V Exxon Valdez oil spill.

The effort of clean up the T/V Exxon Valdez oil spill in Prince William Sound, Alaska, included the use of fertilizers to accelerate natural microbial degradation of stranded oil. A program to monitor various environmental parameters associated with this technique took place during the summer of 1990. Microbiological assays for numbers of heterotrophic and oil-degrading microbes and their hydrocarbon mineralization potentials were performed in support of this program. Fertilizer addition resulted in higher hexadecane and phenanthrene mineralization potentials on treated plots than on untreated reference plots. Microbial numbers in treated and reference surface sediments were not significantly different immediately after the first nutrient application in May 1990. However, subsurface sediments from treated plots had higher numbers of hydrocarbon degraders than did reference sediments shortly after treatment. The second application of fertilizer, later in summer, resulted in surface and subsurface increases in numbers of hydrocarbon degraders with respect to reference sediments at two of the three study sites. Elevated mineralization potentials, coupled with increased numbers of hydrocarbon degraders, indicated that natural hydrocarbon biodegradation was enhanced. However, these microbiological measurements alone are not sufficient to determine in situ rates of crude oil biodegradation.     

Chemical composition of the essential oils of ripe berries of Juniperus oxycedrus L., growing wild in Kosovo

The main objective of this work was to study the essential oil composition of ripe Juniperus oxycedrus L. berries and its natural variation among wild populations in Kosovo. Essential oil was analysed using GC-FID and GC–MS. Plant materials were collected from five locations in Kosovo in August and September of 2011. In total, twenty-seven compounds were identified in the essential oils. The main components were β-myrcene (45.5–56.9%), α-pinene (10.2–36.6%), dl-limonene (3.6–13.8%) and germacrene D (1.7–8.7%). Of the total identified compounds, monoterpenes constituted the highest percentage of all components (70.24–88.22%), followed by oxygenated sesquiterpenes (4.9–11.4%), sesquiterpenes (3.5–11.0%), oxygenated monoterpenes (0.2–2.7%) and oxygenated diterpenes (0.0–1.7). Hierarchical Cluster Analysis (HCA) and Principal Component Analyses (PCA) were used to identify any geographical variations in essential oil composition. Statistical analysis suggests that the clustering of populations is not related to their geographic location, but rather seemed to be linked to local selective forces acting on chemotype diversity.