Search

Over the past century, the demand for petroleum products has increased rapidly, leading to higher oil extraction, processing and transportation, which result in numerous oil spills in coastal-marine environments. As the spilled oil can negatively affect the coastal-marine ecosystems, its transport and fates captured a significant interest of the scientific community and regulatory agencies. Typically, the environment has natural mechanisms (e.g., photooxidation, biodegradation, evaporation) to weather/degrade and remove the spilled oil from the environment. Among various oil weathering mechanisms, biodegradation by naturally occurring bacterial populations removes a majority of spilled oil, thus the focus on bioremediation has increased significantly. Helping in the marginal recognition of this promising technique for oil-spill degradation, this paper reviews recently published articles that will help broaden the understanding of the factors affecting biodegradation of spilled oil in coastal-marine environments. The goal of this review is to examine the effects of various environmental variables that contribute to oil degradation in the coastal-marine environments, as well as the factors that influence these processes. Physico-chemical parameters such as temperature, oxygen level, pressure, shoreline energy, salinity, and pH are taken into account. In general, increase in temperature, exposure to sunlight (photooxidation), dissolved oxygen (DO), nutrients (nitrogen, phosphorous and potassium), shoreline energy (physical advection—waves) and diverse hydrocarbon-degrading microorganisms consortium were found to increase spilled oil degradation in marine environments. In contrast, higher initial oil concentration and seawater pressure can lower oil degradation rates. There is limited information on the influences of seawater pH and salinity on oil degradation, thus warranting additional research. This comprehensive review can be used as a guide for bioremediation modeling and mitigating future oil spill pollution in the marine environment by utilizing the bacteria adapted to certain conditions. [ABSTRACT FROM AUTHOR]

The fate and behavior of diluted bitumen spilled in marine conditions has recently become a topic of much interest, yet, only limited knowledge is available. One of the major issues of a diluted bitumen spill on water is whether the product will sink, especially when suspended sediment is present in the water column. This study demonstrated how weathering processes influenced the key spill-related properties of a diluted bitumen product (Cold Lake Blend-Winter), and how interaction of diluted bitumen with sediment affected its tendency to float or sink in water. This study showed that the weathering states of the oils as well as the size of sediment are important factors influencing oil-sediment interactions and the tendency of the formed oil-particulate aggregates for buoyancy. When mixing with fine- and medium-sized sediments, the fresh to moderately weathered oils formed oil-particulate aggregates and sank in saltwater, while the very heavily-weathered oil formed discrete free-floating tarballs. [ABSTRACT FROM AUTHOR]

Crude oil that is inadvertently spilled in the marine environment can interact with suspended sediment to form oil-mineral aggregates (OMA). Researchers have identified OMA formation as a natural method of oil dispersion, and have sought ways to enhance this process for oil spill remediation. Currently there is a lack of understanding of how the weathering of oil will affect the formation of OMA due to a lack of published data on this relationship. Based on literature, we identified two conflicting hypotheses: OMA formation 1) increases with weathering as a result of increased asphaltene and polar compound content; or 2) decreases with weathering as a result of increased viscosity. While it is indeed true that the viscosity and the relative amount of polar compounds will increase with weathering, their net effects on OMA formation is unclear. Controlled laboratory experiments were carried out to systematically test these two conflicting hypotheses. Experimental results using light, intermediate, and heavy crude oils, each at five weathering stages, show a decrease in OMA formation as oil weathers. [ABSTRACT FROM AUTHOR]

This work investigated effects of a popular oil dispersant (Corexit EC9500A) on oxidation of phenanthrene and pyrene (two model polycyclic aromatic hydrocarbons) in Gulf coast seawater under simulated atmospheric ozone. The degradation data followed a two-stage pseudo-first order kinetics, a slower initial reaction rate followed by a much faster rate in longer time. The ozonation rate for pyrene was faster than that for phenanthrene. The presence of 18 and 180 mg/L of the dispersant inhibited the first-order degradation rate by 32–80% for phenanthrene, and 51–85% for pyrene. In the presence of 18 mg/L of the dispersant, the pyrene degradation rate increased with increasing ozone concentration, but decreased with increasing solution pH and temperature, while remained independent of ionic strength. For the first time, the results indicate that atmospheric ozone may play a significant role in the weathering of dispersed persistent oil components in natural and engineered systems. [ABSTRACT FROM AUTHOR]

This study investigated the effects of 3 model oil dispersants (Corexit EC9500A, Corexit EC9527A and SPC 1000) on photodegradation of pyrene under simulated sunlight. Both Corexit dispersants enhanced photodegradation of pyrene, while SPC1000 slightly inhibited the reaction. Span 80 and Tween 85 were the key ingredients causing the effects, though the underlying mechanisms differed. Span 80 enriches pyrene in the upper layer of water column, whereas Tween 85 induces a photosensitization process. Two reactive oxygen species, 1 O 2 and O 2 − , were found responsible for pyrene photodegradation, though the presence of EC9500A suppressed the 1 O 2 pathway. In terms of photodegradation products, EC9500A enhanced generation of polyaromatic intermediates, i.e., phenaleno[1,9- cd ][1,2]dioxine, 1-hydroxypyrene, and 1,8-pyrenequinone, but did not alter the classical photodegradation pathway. The Corexit dispersants were more prone to photochemical decomposition, with multiple by-products detected. The information aids in our understanding of the effects of dispersants on photochemical weathering of oil compositions. [ABSTRACT FROM AUTHOR]

Zooplankton are suggested to be biotic contributors to the transport and weathering of oil in marine environments due to their ingestion of oil. In the present experiment, feeding activity and microbial communities in feces from Calanus finmarchicus feeding in oil dispersions were characterized. Feeding activity was significantly reduced in oil dispersions. The microbial communities in clean and oil-containing copepod feces were dominated by Rhodobacteraceae family bacteria ( Lesingera , Phaeobacter , Rugeria , and Sulfitobacter ), which were suggested to be indigenous to copepod feces. The results also indicated that these bacteria were metabolizing oil compounds, as a significant increase in the concentrations of viable oil degrading microorganisms was observed in oil-containing feces. This study shows that bacteria in feces from copepods feeding in dilute oil dispersions have capacity for degradation of oil. Zooplankton may therefore contribute to weathering of oil by excreting feces with microbial communities already adapted to degradation of oil. [ABSTRACT FROM AUTHOR]

This work investigated effects of a popular oil dispersant (Corexit EC9500A) on UV- or sunlight-mediated photodegradation of pyrene (a model polycyclic aromatic hydrocarbon) in seawater. The presence of 18 and 180 mg/L of the dispersant increased the first-order photodegradation rate by 5.5% and 16.7%, respectively, and reduced or ceased pyrene volatilization. By combining individual first-order rate laws for volatilization and photodegradation, we proposed an integrated kinetic model that can adequately predict the overall dissipation of pyrene from seawater. Mechanistic studies indicated that superoxide radicals played a predominant role in pyrene photodegradation, and the dispersant enhanced formation of superoxide radicals. 1-Hydroxypyrene was the main intermediate regardless of the dispersant, suggesting that electrons were transferred from excited pyrene to oxygen. In the presence of 18 mg/L of the dispersant, the photodegradation rate increased with increasing ionic strength and temperature, but decreased with increasing HA concentration, and remained independent of solution pH. The results are important in understanding roles of oil dispersants on environmental fate of persistent oil components in natural and engineered systems. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes details of an oil spill model, OILTRANS, developed by the authors. The model is an off-line particle-transport model coupled to the most up to date operational met-ocean model forecasts. Formulations for the dominant oil fate processes of spreading, advection, diffusion, evaporation, emulsification and dispersion have been encoded, providing the model with the ability to accurately predict the horizontal movement of surface oil slick, the vertical entrainment of oil into the water column and the mass balance of spilled oil. The application of the OILTRANS model to an accidental release during a ship-to-ship fuel transfer in the Celtic Sea in February 2009 is presented to validate the system. Comparisons with aerial observations of the oil slick at the time of the incident, and subsequent model simulations, indicate that the OILTRANS model is capable of accurately predicting the transport and fate of the oil slick. [Copyright &y& Elsevier]

This paper reports on the results of weathering studies conducted onfour tight crude oils from production platforms on the northwest shelf of Australia. The laboratory weathering included both evaporative weathering and emulsification studies. The fresh oils and their topped residues were subjected to a battery of physical and chemical characterization analyses. Detailed analyses were performed for n-alkanes by GC/FID and for mono- and polycyclic aromatic hydrocarbons and phenols by GC/MS. The water-in-oil emulsion formation properties of theseoils and their topped residues were investigated at two environmentally significant temperatures (13 and 20 deg.C). The results of the analyses indicate that these oils are very different compositionally and have a wide range of physical and chemical properties. The emulsification properties of these oils and their weathered residues ranged from oils that have very rapid water uptake to oils having no water uptake. Unexpectedly, the very waxy oils had very little water uptake and did not form stable water-in-oil emulsions. [ABSTRACT FROM AUTHOR]

This work follows on extensive empirical studies on the evaporation of oil and petroleum products. A study of the evaporative characteristics of 19 different crude oils and petroleum products was conducted.Best-fit equation parameters were determined for both percentage loss by time and absolute weight loss. All oils except for three (dieselfuel, FCC Heavy Cycle and Bunker C light) were found to fit logarithmic curves. The exceptions noted, fit square root curves with time for periods up to about 5 d. The equation constants were correlated with oil distillation data. The equation constants correlated highly with the percentage distilled at 180 deg.C. Using this correlation, equations were developed by which the oil evaporation can be predicted using the distillation data alone. [ABSTRACT FROM AUTHOR]

Rheological studies were conducted on the water-in-oil emulsions of three crude oils: Arabian Light; Green Canyon; and Sockeye. The emulsions were found to fall into three categories on the basis of both rheological properties and visual appearance: stable; mesostable; and unstable. Stable emulsions are characterized by high viscosities and elasticities and are indefinitely stable. In this study stable emulsions showed true viscosities (viscosity with elasticity separated) approximately 700 times that of the starting oil and mesostable emulsionsapproximately 50 times that of the starting oil. Mesostable emulsions break into water, oil and sometimes emulsion within about 3 d. [ABSTRACT FROM AUTHOR]