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Crude oil spilled at sea is chemically altered through environmental processes such as dissolution, biodegradation, and photodegradation. Transformation of hydrocarbons to oxygenated species increases water-solubility. Metabolites and oxidation products largely remain uncharacterized by common analytical methods but may be more bioavailable to aquatic organisms. Studies have shown that unresolved (i.e. unidentified) polar compounds ('UPCs') may constitute > 90% of the water-accommodated fraction (WAF) of heavily weathered crude oils, but still there is a paucity of information characterizing their toxicological significance in relation to other oil-derived toxicants. In this study, low-energy WAFs (no droplets) were generated from two field-weathered oils (collected during the 2010 Deepwater Horizon incident) and their polar fractions were isolated through fractionation. To allow establishment of thresholds for acute toxicity (LC50) of the dissolved and polar fraction of field collected oils, we concentrated both WAFs and polar fractions to beyond field-documented concentrations, and the acute toxicity of both to the marine copepod Acartia tonsa was measured and compared to the toxicity of the native WAF (non-concentrated). The difference in toxic units (TUs) between the total of the mixture and of identified compounds of known toxicity (polycyclic aromatic hydrocarbons [PAHs] and alkyl phenols) in both WAF and polar fractions was used to estimate the contribution of the UPC to overall toxicity. This approach identified that UPC had a similar contribution to toxicity as identified compounds within the WAFs of the field-weathered oils. This signifies the relative importance of polar compounds when assessing environmental impacts of spilled and weathered oil. [ABSTRACT FROM AUTHOR]

In this study, we investigate the circulation and chemical processes associated with the deposition of the largest oil spill that reached the northeast coast of Brazil during the second half of 2019. Using the Oil Spill Contingency And Response model (OSCAR), we performed both deterministic and probabilistic simulations of oil spills from tanker ships that were present in the sea in the region at the time. The study used a dataset comprising the latitudinal distribution of oil sightings along the coast between 31 August and 2 December 2019 (box plot analysis) provided by the Brazilian Institute of Environment and Renewable Natural Resources (IBAMA). The total amount of oil that reached the coast during this period (approximately 5000 tons) and the date and location of the first sighting (30 August, in the southern part of the state of Paraíba (PB)) were also used as parameters to assess the results of the 31 simulations conducted for ships en route near the area of interest between July and August 2019. The results indicate that a leak having occurred through a mobile source is the most plausible hypothesis for explaining the observed temporal–spatial arrival of the oil leaks along the Brazilian coastline. We suggest that prevention, monitoring, and international cooperation are essential for reducing the risks of future environmental accidents of the kind analyzed in this study and to protect the environment and communities affected. [ABSTRACT FROM AUTHOR]

This study encompasses the analysis of oil spills occurred in the Gulf of Morrosquillo during the loading procedures of oil tankers in the Coveñas maritime Terminal, by means of numerical simulation experiments of the trajectories and weathering processes of oil spilled, which occurred under specific wind, waves, and ocean currents conditions. A three-dimensional (3D) modelling system, OpenOil, which is part of the open-source OpenDrift trajectory framework was used to simulate two contingencies occurred in July and August 2014. During each event, different volumes of Vasconia crude oil spilled on the sea surface were simulated. The resulting slicks were subject to wind drift, Stokes drift from wave forcing, and ocean currents transporting the oil spilled towards the coast. Oil weathering effects (evaporation, emulsification, and biodegradation) are included in the analysis. To calculate weathering of the oil, OpenOil interfaces with the latest version of the open source ADIOS oil library. It should be noted that meteorological and ocean conditions contribute to the oil pathways that in both periods forced the oil slick towards the central coast of the Gulf. The wind speed is an important factor contributing to the rapid evaporation rates of the oil spilled in the warm waters of the Caribbean Sea; hence, allowing a gradual increase of the water fraction, which could lead to the formation of tar balls found in the affected coasts in the areas simulated by the model. The implementation of OpenOil to predict the oil fate and weathering processes in the Colombian basin prove to be a valuable tool that should be used in this maritime terminal to improve planning and preparedness in case of an oil spill. The simulations could be enhanced with higher resolution databases.

In this study, we investigate the circulation and chemical processes associated with the deposition of the largest oil spill that reached the northeast coast of Brazil during the second half of 2019. Using the Oil Spill Contingency And Response model (OSCAR), we performed both deterministic and probabilistic simulations of oil spills from tanker ships that were present in the sea in the region at the time. The study used a dataset comprising the latitudinal distribution of oil sightings along the coast between 31 August and 2 December 2019 (box plot analysis) provided by the Brazilian Institute of Environment and Renewable Natural Resources (IBAMA). The total amount of oil that reached the coast during this period (approximately 5000 tons) and the date and location of the first sighting (30 August, in the southern part of the state of Paraíba (PB)) were also used as parameters to assess the results of the 31 simulations conducted for ships en route near the area of interest between July and August 2019. The results indicate that a leak having occurred through a mobile source is the most plausible hypothesis for explaining the observed temporal–spatial arrival of the oil leaks along the Brazilian coastline. We suggest that prevention, monitoring, and international cooperation are essential for reducing the risks of future environmental accidents of the kind analyzed in this study and to protect the environment and communities affected.

We describe the initial bulk and compound specific composition of the liquid oil spilled during the Deepwater Horizon (DwH) disaster. The emphasis is on the target hydrocarbon compounds typically found in highest concentrations and on those of concern from a toxicological perspective (i.e., the target normal alkanes and isoprenoids, and PAHs on U.S. Environmental Protection Agency’s (EPA) priority list with their alkyl homolog compounds), and/or those relevant for forensic fingerprinting of spill residues (i.e., sulfur containing PAHs and biomarker compounds). Weathering changed the oil’s composition in various environmental compartments. These compositional changes and potential environmental impacts of the remaining weathered residues are presented in this paper. Biodegradation occurred in both surface and subsurface environments while photooxidation primarily modified and removed hydrocarbons in floating oil slicks. The volatile, soluble and highly labile C1 to C10 hydrocarbons were rapidly degraded in the water column and/or emitted to the atmosphere (evaporation). The semi-volatile hydrocarbons (labile C10 to C25) that remained in the water column and floating oil on the water’s surface were lost from oil residues during weathering. The heavy nonvolatile and insoluble hydrocarbons (recalcitrant C25+) were least affected by initial weathering processes in 2010. The composition of the residual oil fraction in surface floating oil was further altered by the addition of oil soluble oxy hydrocarbons produced from photooxidation. During 2011 and 2012 the resulting highly insoluble recalcitrant C25+ oily residues remained on the shorelines, bottom sediments, or bound to suspended particulates in the water column, with detectable residues mostly returning to near pre-spill levels by 2015 to 2020. Some recalcitrant oil residues can still be found at various locations, including some coastal environments (e.g., marshes), or deep-water sediments, at very low levels, ten years after the spill.

Water-in-oil emulsification affects spilled oil fate and exposure, as well as the effectiveness of oil spill response options, via changes in oil viscosity. While oil weathering processes such as evaporation, dissolution, photo-oxidation, and biodegradation increase oil viscosity about 10-fold, incorporation of water droplets into floating oil can increase viscosity by another order of magnitude. The objective of this study was to evaluate how changes in viscosity by oil type, with weathering, and with emulsification affect oil fate. Oil spill modeling analyses demonstrated that the increase in viscosity from emulsification prolonged floating oil exposure by preventing the oil from dispersing into the water column. Persistent emulsified oils are more likely to come ashore than low viscosity oils that readily disperse. Through a rapid increase in viscosity, emulsification restricted entrainment and slowed evaporation. Water column exposure to dissolved concentrations increased with lower viscosity oils. Thus, the ability to emulsify, and at what weathered state, are important predictors of oil fate. Oil viscosity is an important consideration for choosing response alternatives as it controls effectiveness of mechanical removal, in-situ-burning and surface-active chemicals. Therefore, understanding and quantification of oil emulsification are research priorities. The most influential model input determining emulsification and the emulsion’s viscosity is its maximum water content, as it controls the ultimate viscosity of the emulsion. Viscosities were also influenced by the volatile content and initial viscosity of the oil. Algorithms quantifying emulsion stability under field conditions have not been developed, so emulsions were assumed stable over the 30-day simulations. Changes in emulsion stability over time would affect oil properties and so floating oil and shoreline exposures, as well as response effectiveness. However, water column exposures to dissolved concentrations are determined within a few days of oil release, and as such would not be affected by differences in long-term stabilities of the emulsions.

In the GuLF Study, a study investigating possible adverse health effects associated with work on the oil spill response and clean-up (OSRC) following the Deepwater Horizon disaster in the Gulf of Mexico, we used a job-exposure matrix (JEM) approach to estimate exposures. The JEM linked interview responses of study participants to measurement data through exposure groups (EGs). Here we describe a systematic process used to develop transparent and precise EGs that allowed characterization of exposure levels among the large number of OSRC activities performed across the Gulf of Mexico over time and space. EGs were identified by exposure determinants available to us in our measurement database, from a substantial body of other spill-related information, and from responses provided by study participants in a detailed interview. These determinants included: job/activity/task, vessel and type of vessel, weathering of the released oil, area of the Gulf of Mexico, Gulf coast state, and time period. Over 3000 EGs were developed for inhalation exposure and applied to each of 6 JEMs of oil-related substances (total hydrocarbons, benzene, toluene, ethylbenzene, total xylene, and n-hexane). Subsets of those EGs were used for characterization of exposures to dispersants, particulate matter, and oil mist. The EGs allowed assignment to study participants of exposure estimates developed from measurement data or from estimation models through linkage in the JEM for the investigation of exposure-response relationships. [ABSTRACT FROM AUTHOR]

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 conservation of ocean and freshwater have been crucial issues over the past decades, and oil/water separation is a well‐known technology to restore polluted water systems. In the meantime, oil sorbents serve as a promising means of achieving water conservation to recover from oil spills, which require a multi‐factorial approach to review high selectivity, capacity, and rate of oil recovery. However, reusability is a critical component to consider in incidents with large‐scale spills. With the development of sorbent technology, some studies have progressed to explore surface engineering and material design for high oil sorption capacity and durability. Thus, this systemic review, a summary of sorbent developments, serves as a guide to understanding practical applications that can apply to large‐scale oil spills and recognize remaining issues. In this review, the oil weathering process and oil sorption mechanisms in relation to the characteristics of target pollutants are introduced. Then, this comprehensive review focuses on materials in advanced sorbents. These materials have properties including, aligned channels for fast sorption, self‐heating capabilities for viscous oil cleanup, and magnetic‐responsiveness to enhance a collection of final products. The perspective and challenges for the next generation of oil spills remediation technology‐based oil sorbents materials are finally presented in the last section. [ABSTRACT FROM AUTHOR]

During the Deepwater Horizon (DWH) blowout, photooxidation of surface oil led to the formation of persistent photooxidized compounds, still found in shoreline sediments a decade later. Studies demonstrated that photooxidation modified both biodegradation rates of the surface oil and the effectiveness of aerial dispersant applications. Despite the significant consequences of this weathering pathway, the lack of measurements prevented photooxidation to be accounted for in the DWH oil budget calculations and in most predictive models. Here we develop a Lagrangian photooxidation module that estimates the dose of solar radiation individual oil droplets receive while moving in the ocean, quantifies the likelihood of photooxidative changes, and continues to track the transport of these persistent photooxidized compounds. We estimate and track the likelihood of photooxidation of Lagrangian oil droplets in the upper layers of the water column for the DWH case by coupling the net shortwave radiation from NOGAPS to the oil application of the Connectivity Modeling System (oil-CMS). The dose of solar radiation upon a droplet is computed with the intensity of the incoming irradiance at the ocean’s surface, the light attenuation coefficient, and the depth of the oil droplets. Considering a range of DWH empirical irradiance thresholds, we find that photooxidation can happen at short time scales of hours to days, in agreement with the new paradigm of oil photooxidation. Furthermore, the oxidized compounds are likely to form in a 110 km radius around the response site, suggesting that the oil reaching the coastline was already photooxidized. This new dynamic coupling provides a powerful tool to test oil weathering hypotheses, refine the oil budget during the DWH, and ultimately inform rapid response in future oil spills.

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.

There has been increasing urgency to develop methods for detecting oil in sea ice owing to the effects of climate change in the Arctic. A multidisciplinary study of crude oil behavior in a sea ice environment was conducted at the University of Manitoba during the winter of 2016. In the experiment, medium-light crude oil was injected underneath young sea ice in a mesocosm. The physical and thermodynamic properties of the oil-infiltrated sea ice were monitored over a three-week time span, with concomitant analysis of the oil composition using analytical instrumentation. A resonant perturbation technique was used to measure the oil dielectric properties, and the contaminated sea ice dielectric properties were modeled using a mixture model approach. Results showed that the interactions between the oil and sea ice altered their physical and thermodynamic properties. These changes led to an overall decrease in sea ice dielectrics, potentially detectable by remote sensing systems. Unlabelled Image • 330 compounds identified in the oil: 70% of oil mass remained in the ice. • Partitioning of oil in and from sea ice altered its chemical composition. • Decrease of permittivity, thermal conductivity, and density of surfaced oil • Increase of sea ice temperature and decrease of salinity • Overall decrease of the sea ice effective dielectric constant [ABSTRACT FROM AUTHOR]

The Bureau of Ocean Energy Management (BOEM) is responsible for managing the development of US Outer Continental Shelf (OCS) energy and mineral resources. Because oil spills may occur from offshore oil and gas activities, BOEM conducts oil spill risk analysis (OSRA) prior to oil and gas lease sales. Since the 1970s, BOEM has developed and applied the OSRA model to evaluate the risk of potential oil spills to environmental resources. This paper summarizes some of the OSRA model progress and applications in the past decade: (1) calculation of the risk of catastrophic oil spills (with a volume over one million barrels), which concludes that the return period of a catastrophic oil spill in OCS areas is estimated to be 165 years; (2) a more efficient way to estimate the probability of oil spill contact to environmental resources in the Gulf of Mexico; (3) weathering calculations in OSRA, which enhances the accuracy of the OSRA model results; and (4) application of OSRA to the Ixtoc I oil spill as an example of how the OSRA model simulates large oil spills for oil spill preparedness and response.

Photodegradation significantly influences marine oil spill behavior, yet its role remains underrepresented in current models, impairing predictive accuracy. Addressing this, our study rigorously examined oil properties and environmental determinants affecting marine oil spill photodegradation through laboratory simulations. We identified and quantified key factors and their interactions, noting particularly the positive influence of asphaltene and negative implications of oil density. We also discerned a negative correlation between n-alkane degradation and carbon numbers. Our findings underscored the pivotal roles of temperature and irradiance in photodegradation. All tested oils adhered to first-order kinetics, with rate constants ranging from 0.0348 to 0.0645 day−1. Finally, we introduced a novel model incorporating temperature, irradiance and their interactions, ensuring reasonable simulations for marine oil spill photodegradation, fortifying marine oil spill management strategies. [Display omitted] • Marine oil spill photodegradation was simulated under varied conditions. • Effects of oil properties and environmental factors were analyzed and quantified. • Asphaltene, density, temperature and irradiance are key factors to the degradation. • A novel model was developed considering various factors and their interactions. • The model can provide reasonable simulation to the photodegradation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • First application of PSI-MS on photodegraded and degraded spilled oil samples. • PSI-MS is shown to be a suitable technique for spilled oil analysis. • Parameter derived from PSI-MS spectra to estimate the degree of degradation of oils. Abstract Paper spray ionization mass spectrometry (PSI-MS) was applied for the first time to study temporal change of photo-oxidized and weathered oils subjected to degradation. PSI is chosen in this study because it is an optimal ionization technique for the analysis of degraded oils with limited sample quantity and prone to salt and particulate contamination. With PSI-MS, quantitative analysis of oils can be successfully performed with as little as 2 μg of oil sample. In addition, oil solutions containing up to 0.05% sodium chloride were successfully analyzed with PSI-MS. In the PSI-MS spectra of photo-degraded oils, the relative abundance of compounds having double equivalence value (DBE) ≥ 5 increased but those with DBE < 5 decreased in number. The summed abundance ratio of compounds having DBE < 5 and DBE ≥ 5 showed a negative exponential correlation with the duration of UV exposure in laboratory experiments. The same trend was observed from spilled oils obtained from the environment. Therefore, this ratio serves as an effective means to estimate the degree of weathering in spilled oils. [ABSTRACT FROM AUTHOR]

Abstract Oil degradation by surface-level atmospheric ozone has been largely ignored in the field. To address this knowledge gap, this study investigated the ozonation rate and extent of typical petroleum compounds by simulated surface-level ozone, including total petroleum hydrocarbons (TPHs), n -alkanes, and polycyclic aromatic hydrocarbons (PAHs). Moreover, the work explored the effect of a prototype oil dispersant, Corexit EC9500A, on the ozonation rate. Rapid oxidation of TPHs, n -alkanes and PAHs was observed at various gaseous ozone concentrations (i.e. 86, 200 and 300 ppbv). Generally, the presence of the oil dispersant enhanced ozonation of the oil compounds. The addition of humic acid inhibited the reaction, while increasing salinity accelerated the degradation. Both direct ozonation by molecular ozone and indirect oxidation by ozone-induced radicals play important roles in the degradation process. The findings indicate that ozonation should be taken into account in assessing environmental fate and weathering of spilled oil. Graphical abstract Unlabelled Image Highlights • Surface-level atmospheric ozone plays an important role in weathering of oil. • Oil dispersant Corexit EC9500A can accelerate ozonation of oil hydrocarbons. • Oil dispersant Corexit EC9500A enhances generation of hydroxyl radicals. • Both direct and indirect ozonation account for degradation of oil hydrocarbons. • Higher pH and humic acid may inhibit ozonation of oil hydrocarbons. [ABSTRACT FROM AUTHOR]

Abstract The primary aim of this research was to identify the physicochemical properties of the oil and water-in-oil (W/O) emulsions used during a NOFO Oil-on-Water field trials that reduced the performance of the skimmers recovery efficacy during the trials. Extensive studies were performed at SINTEF laboratories with the residues of oil topped (i.e. evaporative loss of crude oil components by distillation process at large scale) for the field trial and compared it with different residues of oil topped by bench scale laboratory procedures. In order to obtain a sufficient stable W/O emulsion for the field trial, bunker fuel oil (IFO380) and various concentrations of an emulsifier (Paramul®) were also added to the residues of oil topped on large scale and investigated through interfacial tension, contact angle, droplet adhesion and "dip and withdraw" tests. The investigations revealed that the addition of an emulsifier lowered the interfacial tension of oil residues, which consequently reduced the adherence properties of the oil and emulsions to the surface of the skimmer material. Too high concentration of an emulsifier (>0,5%) also had a negative effect on the stability of W/O emulsion. Highlights • High concentration of an emulsifier had a negative effect on stability of emulsions. • Addition of an emulsifier lowered the interfacial tension significantly. • Reduced interfacial tension decreased the adherence of an emulsion to skimmer surface. • Controlled laboratory test should be carried out prior to filed testing of skimmers. • During test with adhesion skimmers, use emulsions with optimum viscosities. [ABSTRACT FROM AUTHOR]

We have shown that Bacillus cereus is dominating the bacterial population at three polluted oil-industry sites where weather and soil conditions are extreme in terms of temperature, UV-radiation and salinity. A minor part of the bacterial population includes a strain of Bacillus sonorensis and Pseudomonas stuztzeri . Six bacterial isolates were characterized by MALDI-TOF mass spectrometry. The identity of Bacillus sonorensis was also confirmed by ribotyping using molecular techniques. The extreme conditions result in the limited bacterial diversity at the present sites. Our results indicate that the bacteria have sustained because of their ability to degrade low, medium and high molecular weight hydrocarbons in diesel which were removed by up to 89%, 61% and 92%, respectively by Bacillus sonorensis . Bacillus cereus isolates were less effective, but all showed high activity on high molecular weight hydrocarbons. The study is based on growth tolerance to high diesel toxicity and removal of the three ranges of hydrocarbons. Each isolate showed higher hydrocarbon removal efficiencies when applied separately in biopiles in fresh soil compared to weathered soil. Almost 88% and 25% of the diesel range organics and 23% and 83% of the polyaromatic hydrocarbons were removed from the weathered soil versus the clean, respectively, by Bacillus sonorensis . Such efficiencies were obtained with growth stimulation by addition of nitrogen and phosphorus sources and with Tween-80 as a surfactant. The results are key in an application context, since it is clear that overcoming the recalcitrance of weathered hydrocarbon contaminations to biodegradation is a central issue in for example the Arabian Gulf. Moreover the results emphasize that bioaugmentation/biostimulation with bacteria originally adapted to the site conditions is the way forward since endogenous or exogenous hydrocarbon-degrading bacteria generally are not appropriate for applications that involve weathered hydrocarbon spills. [ABSTRACT FROM AUTHOR]

The 2010 Deepwater Horizon ( DwH ) oil spill contaminated ~ 1,773 km of the Gulf of Mexico shorelines. Yet, few field data are available on the long-term fate and persistency of sediment-retained oil. While an unprecedented amount of oil dispersants was applied, the effects of oil dispersants on desorption of field aged oil remain unknown. This study aimed to investigate the abundance, distributions and physico-chemical availability of the oil retained in Bay Jimmy sediment, Louisiana, five years after the DwH oil spill, and to determine the effects of two model oil dispersants on the desorption potential of the residual oil. Total petroleum hydrocarbons (TPHs), n -alkanes and polycyclic aromatic hydrocarbons (PAHs) in the sediment were analyzed and compared with those in the crude oil and the pre- DwH levels, and batch desorption kinetic tests were carried out to quantify the dispersant effects on the desorption rate and extent. The biomarker hopanes profile and diagnostic ratio were analyzed, which confirmed the origin and persistence of the sediment-retained oil. After five-year natural weathering, the oil level in the sediment remained orders of magnitude higher than the pre-spill level. Nearly all low-molecular-weight n -alkanes and 2-ring PAHs had been degraded. Oil dispersants, SPC 1000 and Corexit EC9500A, were able to enhance solubilization of the sediment-retained oil upon resuspension of the sediment. Successive desorption experiments indicated that 71.6% of TPHs, 74.8% of n -alkanes, and 91.9% of PAHs in the sediment remained highly stable and hardly desorbable by seawater; yet, addition of 18 mg/L of SPC 1000 enhanced the desorption and lowered these fractions to 57.3%, 68.1%, and 81.4%, respectively. The findings are important for understanding the natural weathering rate and persistence of oil residual and the effects of dispersants on the physical and biological availabilities of aged oil in coastal sediments. [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]

Sustainability of vegetable oil-based biodiesel has been a controversial issue since its invention as an alternative to conventional diesel. In this study, the Inclusive Impact Index (Triple I) is applied to evaluate the trade-off between advantages and disadvantages of the biodiesel system. Triple I is a single quantitative index for sustainability assessment, which is based on ecological footprint (EF), biocapacity (BC), ecological risk (ER), human risk (HR), cost (C) and benefit (B) under the life cycle (LC) approach. Due to the lack of appropriate guidelines for calculation, the application of Triple I is varied and limited. With respect to contribution to sustainability assessment of renewable energy for transportation, this study aims to propose a methodical estimation of Triple I by integrating its current principles within the Life Cycle Sustainability Assessment (LCSA) framework. The entire study is presented in two parts: Part I identifies and describes the methodological framework of the Triple I - LCSA integration, whilst Part II involves assumed exemplifications on the application of the Triple I framework attached with the case study of an inedible vegetable oil-based biodiesel system in Ha Long Bay, Vietnam. In the first part, an integration framework of the Triple I and LCSA was developed. Accordingly, human health impacts (DALY person −1 ) and ecosystem quality impacts (PDF m −2 year −1 ) from IMPACT 2002+ and Lethal/Effective Concentration (LC/EC) (under ecotoxicity assessment) are adopted as HR and ER in Triple I, respectively. Life cycle-based EF and life cycle costing are used for EF and C and B, respectively. Under the newly developed framework, ecosystem impacts and human health impacts are firstly converted to a monetary value, then to global hectares in line with cost and benefit values. Following the success developed in the Triple I framework, this work introduces to the sustainable assessment community, especially the transportation sector, a convenient and easy-to-apply quantitative index. Furthermore, this paper also summarizes several state-of-art life cycle assessment techniques and provides brief information about biodiesel life cycle inventories and some potential impacts of the system. [ABSTRACT FROM AUTHOR]

A simple and flexible correlation has been developed for the prediction of the kinematic viscosity of crude oils based on the Walther equation (1931). The correlation was developed in order to improve on the accuracy of existing correlations and to assist oil spill weathering models, reservoir models and other models where the knowledge of viscosity of uncharacterised crude oils is required. The data used to build the correlation consist of measurements from 137 crude oils from various locations around the world, with 254 viscosity measurements taken at two temperatures, 0 °C and 15 °C, resulting in kinematic viscosity values ranging from 2 cSt to 9,000,000 cSt. The correlation can be used in three different ways depending on the available data. When a single viscosity measurement is available, it can predict the viscosity at a different temperature with an average absolute deviation (AAD) of 13.7% for the studied temperature range. When the specific gravity (SG) and the 50% mass boiling point is available it can give a viscosity estimation with an AAD of 52.9%, which is an improvement in accuracy by a factor of two compared to previously published correlations with the same inputs. Finally, when only the 50% mass boiling point is available, we have improved the accuracy of the Mehrotra (1995) correlation by 10%. [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]

A numerical study using coupled models was performed to investigate the Tramandaí beach oil spill. The hydrodynamic three-dimensional TELEMAC3D and the ECOS model, an oil model being developed at the Universidade Federal do Rio Grande, were coupled and used to carry out a simulation of the oil spill event that occurred on the January 26, 2012 along the Tramandaí coast in the Southern Brazilian shelf. Oil drift results indicate that the oil reaches the coastline after 10 h. The final position, the extension of the spill and the time required for the oil to reach the coastline are corroborated by the observations based on the Brazilian environmental agency report. The winds and currents are the major physical forcing controlling the oil behavior and the final destination. The weathering properties of the oil indicate the formation of an emulsion with a water content of 69% and an increase of 45 kgm −3 in oil density due to the incorporation of water in the emulsification process and mass loss via evaporation. The final oil mass balance indicates that nearly 15% of the oil mass is lost due to evaporation. [ABSTRACT FROM AUTHOR]

In case of oil spills due to disasters, one of the environmental concerns is the oil trajectories and spatial distribution. To meet these new challenges, spill response plans need to be upgraded. An important component of such a plan would be models able to simulate the behaviour of oil in terms of trajectories and spatial distribution, if accidentally released, in deep water. All these models need to be calibrated with independent observations. The aim of the present paper is to demonstrate that significant support to oil slick monitoring can be obtained by the synergistic use of oil drift models and remote sensing observations. Based on transport properties and weathering processes, oil drift models can indeed predict the fate of spilled oil under the action of water current velocity and wind in terms of oil position, concentration and thickness distribution. The oil spill event that occurred on 31 May 2003 in the Baltic Sea offshore the Swedish and Danish coasts is considered a case study with the aim of producing three-dimensional models of sea circulation and oil contaminant transport. The High-Resolution Limited Area Model (HIRLAM) is used for atmospheric forcing. The results of the numerical modelling of current speed and water surface elevation data are validated by measurements carried out in Kalmarsund, Simrishamn and Kungsholmsfort stations over a period of 18 days and 17 h. The oil spill model uses the current field obtained from a circulation model. Near-infrared (NIR) satellite images were compared with numerical simulations. The simulation was able to predict both the oil spill trajectories of the observed slick and thickness distribution. Therefore, this work shows how oil drift modelling and remotely sensed data can provide the right synergy to reproduce the timing and transport of the oil and to get reliable estimates of thicknesses of spilled oil to prepare an emergency plan and to assess the magnitude of risk involved in case of oil spills due to disaster. [ABSTRACT FROM AUTHOR]

Due to the sudden nature of oil spills, few controlled studies have documented how oil weathers immediately following accidental release into a natural lake environment. Here, we evaluated the weathering patterns of Cold Lake Winter Blend, a diluted bitumen (dilbit) product, by performing a series of controlled spills into limnocorrals installed in a freshwater lake in Northern Ontario, Canada. Using a regression-based design, we added seven different dilbit volumes, ranging from 1.5 to 180 L, resulting in oil-to-water ratios between 1:71,000 (v/v) and 1:500 (v/v). We monitored changes in the composition of various petroleum hydrocarbons (PHCs), including n -alkanes, polycyclic aromatic hydrocarbons (PAHs), and oil biomarkers in dilbit over time, as it naturally weathered for 70 days. Depletion rate constants ( k D ) of n -alkanes and PAHs ranged from 0.0009 to 0.41 d -1 and 0.0008 to 0.38 d -1 , respectively. There was no significant relationship between k D and spill volume, suggesting that spill size did not influence the depletion of petroleum hydrocarbons from the slick. Diagnostic ratios calculated from concentrations of n -alkanes, isoprenoids, and PAHs indicated that evaporation and photooxidation were major processes contributing to dilbit weathering, whereas dissolution and biodegradation were less important. These results demonstrate the usefulness of large scale field studies carried out under realistic environmental conditions to elucidate the role of different weathering processes following a dilbit spill.

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]

A state-of-the-art review of fate and transport modelling of oil spills is presented. Emphasis is placed on oil spills in ice-covered waters. The review encompasses advection, spreading, evaporation, dissolution, dispersion, emulsification, biodegradation, encapsulation, sedimentation and photo-oxidation processes. The current understanding of these processes and algorithms to describe and model them are discussed. Quantitative studies of oil spills in open and dynamic ice conditions are also reviewed. The review identifies the current knowledge gaps and future research directions. [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]

We examined the degree of DNA damage caused by three fractions (F1, aliphatic hydrocarbons; F2, aromatic hydrocarbons; and F3, polar compounds) of the organic extract of sediments taken from Taean, Korea, following the Hebei Spirit oil spill. DNA damage was measured using the comet assay with blood cells of the striped beakfish ( Oplegnathus fasciatus ). DNA damage was also examined for fractions of crude oil (Iranian Heavy Crude Oil, IHC), weathered oil and six subfractions (F2.1–F2.6). The greatest DNA damage was found from the Sinduri dune region and DNA damage decreased to 40% weathered oil in F2 fraction compared with crude oil. The DNA damage of the sum of fractions was found higher than the organic extracts of sediments, suggesting antagonistic interactions between the genotoxic compounds. This study confirmed the persistence of potential genotoxicity in sediments of the severely affected regions as long as 5 years after the oil spill. [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]

Mechanical oil recovery (i.e., booming and skimming) is the most common tool for oil spill response. The recovered fluid generated from skimming processes may contain a considerable proportion of water (10 % ~ 70 %). As a result of regulatory prohibition on the discharge of contaminated waters at sea, vessels and/or storage barges must make frequent trips to shore for oil-water waste disposal. This practice can be time- consuming thus reduces the overall efficiency and capacity of oil recovery. One potential solution is on-site oil-water separation and disposal of water fraction at sea. However, currently available decanting processes may have limited oil/water separation capabilities, especially in the presence of oil-water emulsion, which is inevitable in mechanical oil recovery. The decanted water may not meet the discharge standards and cause severe ecotoxicological impacts. This paper therefore comprehensively reviews the principles and progress in oil/water separation, demulsification, and on-site treatment technologies, investigates their applicability on decanting at sea, and discusses the ecotoxicity of decanted water in the marine environment. The outputs provide the fundamental and practical knowledge on decanting and help enhance response effectiveness and consequently reducing the environmental impacts of oil spills. [Display omitted] • Compared physical and chemical separation and water treatment for on-site decanting. • Capacity, adaptability, and pollution of different techniques are summarized. • Assessed the ecological impacts of dispersed oil and demulsifier. • Provided scientific support for the decision making to the on-site decanting. [ABSTRACT FROM AUTHOR]

The state-of-art in oil spill modelling methods is summarized, focusing on development since 2000. Some recommendations for possible application of these methods to the south-eastern part of the Baltic Sea are prepared. Particular attention is paid on the methods of parameterization of volume of oil spill and calculation of advection of the oil spills. Consideration is also given to methods used in oil weathering models. [ABSTRACT FROM AUTHOR]

Highlights: [•] We monitored toxicity of intertidal sediments for 5years after Hebei Spirit oil spill. [•] Toxicity of sandy beaches decreased within 8months after the spill. [•] Sediment toxicity remained at heavily contaminated sites 5years after the spill. [•] Ecological impact and weathering process of residual oils are ongoing. [Copyright &y& Elsevier]

Abstract: Oil exposure has been shown to be detrimental to several salt marsh plants however little information is available for Juncus roemerianus. Thirty-two mesocosms were established with J. roemerianus sod and replicate marshes were exposed to Louisiana sweet crude oil to test oil dose (6, 12, and 24Lm−2) and weathering (oil weathered for 0days, 3days, and 3weeks). Juncus were monitored following oil exposure for culm survival, photosynthetic rates, and C-assimilation rates. Oil dosage had a significant effect among wetlands with low-dose (6Lm−2) mesocosms having higher culm survival, photosynthetic rates, and C-assimilation rates than medium or high dose wetlands (12 or 24Lm−2). Oil weathering did not elicit significant differences between treated wetlands however full strength wetlands (un-weathered oil) consistently had the lowest culm survivorship, photosynthetic rates, and C-assimilation rates. From our results, J. roemerianus marshes may be very susceptible to oil exposure. [Copyright &y& Elsevier]

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]

A large-scale assessment of polycyclic aromatic hydrocarbons (PAHs) from the 1991 Gulf War oil spill was performed for 2002–2003 sediment samples (n = 1679) collected from habitats along the shoreline of Saudi Arabia. Benthic sediment toxicity was characterized using the Equilibrium Partitioning Sediment Benchmark Toxic Unit approach for 43 PAHs (ESBTUFCV,43). Samples were assigned to risk categories according to ESBTUFCV,43 values: no-risk (≤1), low (>1–≤2), low-medium (>2–≤3), medium (>3–≤5) and high-risk (>5). Sixty seven percent of samples had ESBTUFCV,43 > 1 indicating potential adverse ecological effects. Sediments from the 0–30 cm layer from tidal flats, and the >30–<60 cm layer from heavily oiled halophytes and mangroves had high frequency of high-risk samples. No-risk samples were characterized by chrysene enrichment and depletion of lighter molecular weight PAHs, while high-risk samples showed little oil weathering and PAH patterns similar to 1993 samples. North of Safaniya sediments were not likely to pose adverse ecological effects contrary to sediments south of Tanaqib. Landscape and geomorphology has played a role on the distribution and persistence in sediments of oil from the Gulf War. [Copyright &y& Elsevier]

Abstract: Polycyclic aromatic compounds (PACs) of petrogenic origin are widespread contaminants of the environment. We investigated the weathering and biodegradation of fuel oil PACs in microcosms that contained natural soil or natural soil primed by adding bioremediated soil to a 2% concentration. In the primed soil, lag-phases were shorter, and biodegradation was more pronounced. To describe PAC degradation, changes in the relative distribution of PACs and changes in isomer ratios, that are specific for biodegradation, were determined by univariate and multivariate techniques. A multivariate approach based on normalized areas or isomer ratios, in combination with principal component analysis, provided the most detailed description of weathering and biodegradation. In particular, the sequence of degradation of PACs was more transparent when using the multivariate approach. We also identified new diagnostic ratios of dimethylphenanthrenes for use in the study of moderately and severely biodegraded samples. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Many sediments are contaminated with mixtures of oil residues and polycyclic aromatic hydrocarbons (PAHs), but little is known about the toxicity of such mixtures to sediment-dwelling organisms and the change in toxicity on weathering. In the present study, we investigated the effects of a seminatural, two-year weathering period on PAH/oil chemistry and toxicity in a marine sediment that had been spiked with three different oils (a gas oil, a lubricating oil, and a crude oil; all tested at five concentrations). Toxicity of bioavailable, pore water--accommodated oil/PAH fractions was quantified using a bacterial (Vibrio fischeri) assay and the in vitro chemical-activated luciferase expression assay (DR-CALUX; using conditions to detect PAHs). Results of chemical analyses pointed to (microbial) degradation of all three oils: Sediment oxygen demand during weathering increased with increasing oil concentration, total oil concentrations decreased to between 17 and 29% of initial levels, and resolved n-alkanes were depleted in weathered oil fractions. Furthermore, a shift in the relative importance of different boiling-point fraction ranges of the oils was observed on weathering. Generally, the lowest fraction range (C10-C16) disappeared, whereas the relative proportion of the highest (C28-C40) fraction range increased considerably. Remarkably, for the gas oil, this fraction shift was dependent on the oil concentration in sediment. Similarly, degradation of PAHs was strongly affected by the sedimentary oil content, indicating that the presence of oil stimulated PAH degradation. This phenomenon applied to both low- and high-molecular-weight PAHs, although the first group (3- and 4-ring PAHs) was degraded most. Results from the V. fischeri and DR-CALUX assay showed that in most cases, pore-water toxicity decreased on weathering. Combining the assay responses with chemical data indicated that the observed toxicity probably was not caused by the analyzed PAHs but, rather, by specific oil constituents instead. [ABSTRACT FROM AUTHOR]

To effectively determine the fate of spilled oil in the environment and to successfully identify the source(s) of spilled oil and petroleum products is extremely important in many oil-related environmental studies and liability cases. This article briefly reviews the most recent developments and advances of the gas chromatography-based technologies that are most frequently used in oil-spill characterization and identification studies. The effects of oil weathering on the chemical composition features and changes of spilled oils in the environment are also addressed. The fingerprinting and data interpretation techniques discussed include recognition of distribution patterns of petroleum hydrocarbons, oil type screening and differentiation, analysis of "source-specific marker" compounds, determination of diagnostic ratios of specific oil constituents, and application of various statistical and numerical analysis tools. [ABSTRACT FROM AUTHOR]

The multiple agencies who sponsored The Long-Term Fate Workshop provided an opportunity to identify and prioritize research opportunities as they relate to the long-term weathering of oil. Workshop participants identified 15 areas needing research and ranked these areas by priority and level of effort. A short description of the research needs is presented here in the context of the “life history” of an oil spill. [Copyright &y& Elsevier]