Fresh Crude Oil Research Articles

Crude oil pollution effect on agricultural soil properties and germination of bean (<i>Vigna unguiculata(/i) L.) seed

Crude oil pollution affects not only soil properties but also seed germination. The aim of thisresearch is to checkmate the effect crude oil pollution has on soil fertility, seed germinationand microbial activity. Two different agricultural soils from Ibeno and Otuocha collected bycomposite sampling were used to conduct the study. The crude oil for carrying out the research was sterilized with a micron Chromafil CA/S % 45 syringe filters. The physicochemical analysis of the soil and its microbiological enumeration was done. This was followed by the artificial pollution of the soil with fresh crude oil. Soil’s physicochemical properties and microbiological enumeration were analyzed followed by the planting of bean seed son the polluted soil. Unpolluted soils was also planted and served as the control. The artificial pollution of the soils’ increased physicochemical properties like cation exchange capacity, selenium, mercury, arsenic, carbon and phosphorus in both soil. Some physicochemical properties like electrical conductivity, salinity, vanadium, zinc, cadmium, iron, manganese, copper, cobalt, nickel and nitrogen decreased in both soils. Water permeability was positive and became negative after pollution. Soil texture was bound and became loose after pollution. Other soil properties like pH increased in Ibeno soil but decreased in Otuocha soil. The number of microorganisms decreases after pollution. Statistically, cultivated beans germinated faster on unpolluted soil and appear healthier than polluted soil because of slow germination and a wrinkled appearance. This study shows that crude oil pollution has a significant effect on soil fertility, seed germination and microbial activity.

Transcriptome analysis of a springtail, Folsomia candida, reveals energy constraint and oxidative stress during petroleum hydrocarbon exposure

Petroleum hydrocarbon (PHC) contamination in soil is ubiquitous and poses harmful consequences to many organisms. The toxicity of PHC-impacted soil is difficult to predict due to variations in mixture composition and the impacts of natural weathering processes. Hence, high-throughput methods to assess PHC-impacted soils is required to expedite land management decisions. Next-generation sequencing is a robust tool that allows researchers to investigate the effects of contaminants on the transcriptome of organisms and identify molecular biomarkers. In this study, the effects of PHCs on conventional endpoints (i.e., survival and reproduction) and gene expression rates of a model springtail species, Folsomia candida were investigated. Age-synchronized F. candida were exposed to ecologically-relevant concentrations of soils spiked with fresh crude oil to calculate the reproductive EC25 and EC50 values using conventional toxicity testing. Soils spiked to these concentrations were then used to evaluate effects on the F. candida transcriptome over a 7-day exposure period. RNA-seq analysis found 98 and 132 differentially expressed genes when compared to the control for the EC25 and EC50 treatment groups, respectively. The majority of up-regulated genes were related to xenobiotic biotransformation reactions and oxidative stress response, while down-regulated genes coded for carbohydrate and peptide metabolic processes. Promotion of the pentose phosphate pathway was also found. Results suggest that the decreased reproduction rates of F. candida exposed to PHCs is due to energy constraints caused by inhibition of carbohydrate metabolic processes and allocation of remaining energy to detoxify xenobiotics. These findings provide insights into the molecular effects in F. candida following exposure to crude oil for seven days and highlight their potential to be used as a high-throughput screening test for PHC-contaminated sites. Adverse molecular effects can be measured as early as 24 h following exposure, whereas conventional toxicity tests may require a minimum of four weeks.

Variation of stretching tension and breaking tendency of floating fresh South Louisiana crude oil with slick thickness

Floating crude oil patches can separate from the main oil slicks depending on oil characteristics and sea conditions. The breaking tendency of smaller oil patches from the fresh crude oil slicks vary depending on oil type and thickness of the oil slick. Some oil slicks have high breaking tensions that can support significant weight. We investigated the breaking tension of fresh crude oil (South Louisiana crude oil (MC 252)) floating on water in relation to oil layer thickness. We observed that there is a critical thickness (CT) at which the floating oil exhibits significantly high breaking tension, and it becomes difficult for oil patches to break off. Below the CT, the floating oil layer was too thin and broke off easily. Above the CT, the oil layer was too thick, and external forces caused larger oil to stretch to form larger globules that broke off from the main floating oil until the oil layer thickness was reduced to CT. For the fresh crude oil tested, we estimate the maximum breaking tension as 0.23 ± 0.02 N/m and occurred at oil layer thickness of 0.16 mm. When the oil layer was thicker than the CT, the breaking tension was significantly lower (0.03 ± 0.02 N/m) and larger oil globules separated from the floating oil easily. These observations explain the conditions that lead to formation of highly stable oil patches at sea that can remain floating and travel long distances, some eventually depositing at beaches and in shallow waters as large oil patches.

Effect of ultrasonic homogenization on crude oil-water emulsion stability

This research aims to evaluate the effect of ultrasonic processing parameters (power and sonication time), emulsion characteristics (water salinity and pH) and their interaction on oil-in-water emulsion stability for Cold Lake Blend (CLB) crude oil. Response surface methodology was used to design experimental runs, in which the parameters were investigated at five levels. Emulsion stability was evaluated by measuring creaming index, emulsion turbidity and microscopic image analysis. The effect of crude oil condition (fresh and weathered) on the emulsion stability was also investigated at the optimum sonication parameters and emulsion characteristics. The optimum condition was found at a power level of 76–80 W, sonication time of 16 mins, water salinity of 15 g/L NaCl, and pH of 8.3. Increasing sonication time beyond the optimum value had adverse effect on the emulsion stability. High water salinity (> 20 g/L NaCl) and pH (> 9) decreased the emulsion stability. These adverse effects intensified at higher power levels (> 80–87 W) and longer sonication times (> 16 mins). Interaction of parameters showed that the required energy to generate stable emulsion was within 60 − 70 kJ. Emulsion with fresh crude oil was more stable than those generated with the weathered oil.

Native bacteria isolated from weathered petroleum oil-contaminated soils in Tabasco, Mexico, accelerate the degradation petroleum hydrocarbons in saline soil microcosms

Bioremediation is an environmentally sound and cost-effective strategy to restore soils contaminated with petroleum oil. In this study, native bio-surfactant-producing bacteria able to use polycyclic aromatic hydrocarbons (PAHs: anthracene [ANT] or phenanthrene [PHE]) as their sole carbon source were isolated from soil contaminated with weathered petroleum oil (WPO) collected near “La Venta” gas processing complex, in Tabasco, Mexico. Bacteria able to grow in 200 ppm of ANT or PHE and having high bio-surfactant activity were selected. Included were bacteria identified as Sphingobium sp., Bosea sp., Pseudomonas sp., Rhodococcus sp. and Phenylobacterium sp. Different consortia of these bacteria ± bio-stimulation with glucose, ammonium nitrate, or both, were examined for their capacity to degrade either WPO or fresh crude petroleum oil (FCPO) in soil microcosms. No efficient short-term (24 days) degradation of WPO using bio-augmentation and bio-stimulation strategies was possible using two bacterial consortia conformed by combinations of these bacterial isolates. Best results were obtained with a consortium composed of Pseudomonas cloritidismutans and Rhodococcus qingshengii, identified by 16S rRNA sequencing, which led to an 86% reduction of FCPO contaminants in soil microcosms, 90 days after treatment. However, the bioremediation efficiency of this consortium was significantly reduced by moderate salinity levels in the soil. Although promising, these results highlight the adverse effect that weathering and/or salinity may have on the remediation of petroleum oil-contaminated soils.

Evaluation and Comparison of Current Emulsification Algorithms and Their Uncertainty in Oil Spill Modeling Software

Oil spill risk assessments (OSRAs) do not currently distinguish between potentially more toxic, fresh crude oil and less toxic, highly-weathered residues which limits the understanding of the highest risk areas to prioritize mitigation measures and allocate response resources. Fate and trajectory models, used commonly for OSRA, have advanced significantly over the last five years now with enhanced ability to model chemical and physical parameters at greater resolution. Using this enhanced resolution, modelers may be able to provide some indication of the weathered state of the oil as input to the OSRA. In order to evaluate the degree of certainty in such a prediction, it is necessary to better understand the uncertainty in the modeled weathering processes that influence the toxicity of the oil. Emulsification plays a significant role in modeling of oil thickness (and therefore photo-modification), evaporation, and dissolution which are important modulators of oil toxicity. In this project, the emulsification algorithms of three currently available fate and trajectory models, ADIOS, OILMAP/SIMAP, and OSCAR, were evaluated to gain a better understanding of the degree of certainty in the modeled weathered state of oil. In this work, the basis of emulsification algorithms implemented in the models referenced above were identified, and it was found that each of these models incorporates emulsification differently. ADIOS2 relies on emulsification data gathered from mixing oil and water in a food processor. An updated version of ADIOS2 (ADIOS3) is based on a new formulation that is dependent on measured SARA components of the oil, but is still under construction and is not yet implemented. OILMAP/SIMAP use the algorithm presented in Mackay and Zagorski (1982). OSCAR uses a water uptake algorithm that was calibrated to in-house laboratory experiments. Further investigation into the development of each of these emulsification algorithms provided insight into the degree of uncertainty in these models and their input parameters, and what oil types may not be appropriately characterized by the implemented emulsification model. Additionally, the impact of that uncertainty on oil fate was investigated by evaluating the changes in the amount of emulsification when modifying user input parameters within realistic assumption ranges. The findings and comparison of the implementation of these emulsification algorithms and the sensitivity of the results to different inputs is presented here.

Evaluation of wettability alteration in heterogeneous limestone at microscopic and macroscopic levels

Wettability controls the location, distribution, and flow of fluids in a pore network. Obtaining a uniform core scale wettability distribution is therefore a necessary condition for reliable special core analysis (SCAL). In the present work, dynamic and static aging procedures were used to alter the wettability of outcrop Edwards limestone, and Amott-Harvey cycles were performed on whole and split core samples to evaluate wetting distribution and stability. Dynamic aging was observed to be more efficient and produced a more uniform and reproducible wettability distribution compared to static aging. Rock-fluid and fluid-fluid interactions, evaluated by Isothermal Titration Calorimetry (ITC) experiments, confirm that supplying fresh crude oil during the aging procedure to a core plug causes the greatest wettability change. Synergy between ITC and simple core scale experiments provide an improved understanding of the wettability alteration at microscopic and macroscopic levels in heterogeneous Edwards limestone.

Time Evolution and Effect of Dispersant on the Morphology and Viscosity of Water-In-Crude-Oil Emulsions.

This study examines the time evolution and effects of adding dispersant (Corexit 9500A) at varying concentrations on the microscopic morphology and bulk viscosity of saltwater-in-crude-oil (Louisiana) mechanically mixed emulsions. Rheology is used for measuring the viscoelastic properties and viscosity, the latter at varying shear rates. Microscopy, followed by machine-learning-based analysis, is used for characterizing the size and spatial distribution of the water droplets in the emulsions. Initially, the water droplets appear as a multiscale lattice with a Sauter diameter of 5.3 μm and a polydispersity of 0.43, with small droplets aggregating around large ones. The corresponding bulk viscosity decreases with increasing shear rate from 2 orders of magnitude to 5 times higher than that of the weathered crude oil. After 7 days, the number of submicron droplets increases, the nearest-neighbor distance decreases, indicating preferential aggregation, and the viscosity increases by 56-112% at high shear rates (5-100 s-1). After 14 and 21 days, some droplets coalesce resulting in loss of clusters and a decrease in viscosity. These trends suggest that changes in the aggregation contribute to the variations in viscosity. Subsequent analysis applies previously developed models for the effect of aggregation on the properties of the emulsion. While the reduction in viscosity is predicted by this model, matching of rates requires modification to the assumed relationship between yield stress and interdroplet forces. Adding dispersant without mixing generates Marangoni-driven flows as the water droplets coalesce. In time, part of the water separates, a fraction forms clouds of submicron droplets, and the rest remains unchanged. Mixing dispersant at low concentration with the emulsion accelerates the coalescence and phase separation. The removed water fraction increases with dispersant concentration, reaching 99.6% for a dispersant-to-emulsion concentration of 10-3. The remaining emulsion consists of fine droplets with Newtonian viscosity that is still 4 times higher than that of the fresh crude oil but only 14% higher than that of the weathered oil.

Chemical composition of Bakken crude oil burn residue: Environmental relevance following train derailment fires

Shipments of Bakken crude oil by rail have increased in concert with the production of unconventional crude oil in the Williston Basin over the past 10 years, during which time multiple fiery train derailments resulted in tragic loss of life and/or environmental impacts. In this study the compositions of Bakken oil burn residues from a derailment fire(s) are compared to fresh and laboratory-evaporated Bakken crude oil. The absolute and hopane-normalized concentrations of n-alkanes, unsubstituted and substituted PAHs, and petroleum biomarkers and their percent depletions and enrichments (relative to hopane) are reported. Bakken oil burn residues lost 67–78% of their total chromatographable mass (C5 to C44) and exhibit chemical trends distinct from naturally-evaporated oil, including (1) the shape of their UCM profiles, (2) depletion of n-alkanes up to (at least) n-C30, (3) enrichment of priority pollutant (pyrogenic) PAHs, specifically favoring PAH isomers containing three or more linear aromatic rings (anthracene or benz[a]anthracene) or 5-member rings (fluoranthene or indeno[1,2,3-c,d]pyrene), and (4) depletion of some lower boiling petroleum biomarkers (C23-C25 tricyclic terpanes). Despite relative enrichment of most priority pollutant PAHs the absolute concentrations of both total PAH (TPAH50) and priority pollutant PAH (PPAH16) in the burn residues were depleted 69–78% and 41–48%, respectively, compared to fresh Bakken oil. These results demonstrate the changes and range of compositions among fresh, evaporated, and variably-combusted residues of Bakken crude oil, the latter of which are important in assessing the potential effect(s) of burn residues on the environment proximal to train derailment fires.

Experimental study of C-band microwave scattering characteristics during the emulsification process of oil spills

In this study, oil spill experiments were performed in a water tank to determine changes in the surface scattering characteristics during the emulsification of oil spills. A C-band fully-polarimetric microwave scatterometer and a vector network analyzer were used to observe films of the following oils: crude oil with an asphalt content below 3% that is prone to emulsification (type A), fresh crude oil extracted from an oilfield (type B), and industrial crude oil that was dehydrated and purified (type C). The difference in the backscatter results between the emulsified oil film and the calm water surface under C-band microwaves and the influence of the emulsification of the oil film on the backscatter were analyzed in detail. The results demonstrate that under a low-wind and no-waves condition (the maximum wave height was below than 3 mm), the emulsification of crude oil could modulated the backscatter through changes in the surface roughness and the dielectric constant, where the surface roughness had the dominant effect. The surface backscatters of the type B oil were greater than that of the type C oil in both the emulsified and non-emulsified states. In the non-emulsified state, the average differences in the backscatter between the type B and C oils were 2.19 dB, 2.63 dB, and 2.21 dB for the polarization modes of VV, HH, and HV/VH, respectively. Smaller corresponding average differences of 0.98 dB, 1.49 dB, and 1.5 dB were found for the emulsified state with a 20% moisture constant for the oil film. The results demonstrated that the surface roughness of the different oil films could vary due to the differences in the oil compositions and the oil film properties, which in turn affect the backscatter of the oil film surface.

Size exclusion chromatography reveals a key parameter of demulsifiers for enhanced water separation from crude oil emulsions

Demulsifier is used in gas oil separation plants for the separation of water from crude oil emulsion. One of the important parameters for the enhancement of performance is the optimization of demulsifier formulation with respect to oil composition and produced water chemistry. The consistency in the quality of the formulation is essential to obtain the best separation of water throughout the production period of crude oil. The industry accepted method to optimize formulations is the bottle test method. However, this method remains laborious, time-consuming, imprecise, and requires access to fresh crude oil, which is not convenient from a practical viewpoint. Instead, routine physical and chemical properties are monitored to ensure the consistency of the demulsifier quality. It was, however, observed that there was a significant influence on the performance of a demulsifier from different batches with very close physical and chemical properties. Therefore, we developed a method using size exclusion chromatography to determine the molecular weight distribution of demulsifier base material, in this case, alkoxylated alkylphenol-formaldehyde resin. It was found that all the samples contained two well-separated species with one low molecular weight of about 2700 g/mol and other one with high molecular weight of about 15000 g/mol. The variation in the content of low and high molecular weight species was identified to be a key parameter significantly influencing the separation performance. It is apparent from this study that size exclusion chromatography could provide some additional insights on demulsifier intermediate chain length dispersity which could be correlated to actual separation performance.

Determinants of airborne benzene evaporating from fresh crude oils released into seawater

Benzene, toluene, ethylbenzene, xylenes, naphthalene and n-hexane evaporating from a thin oil film was measured for 30 min in a small-scale test system at 2 and 13 °C and the impact of physicochemical properties on airborne benzene with time after bulk oil release was studied. Linear mixed-effects models for airborne benzene in three time periods; first 5, first 15 and last 15 min of sampling, indicated that benzene content in fresh oil, oil group (condensate/light crude oil) and pour point were significant determinants explaining 63–73% of the total variance in the outcome variables. Oils with a high pour point evaporated considerably slower than oils with a low pour point. The mean air concentration of total volatile organic compounds was significatly higher at 13 °C (735 ppm) compared to 2 °C (386 ppm) immediately after release of oil, but at both temperatures the concentration rapidly declined.

Solid separation from the heavy oil sludge produced from Liaohe Oilfield

Heavy oil sludge usually exists in the form of stable W/O emulsion, in which the water droplets were stabilized by natural surfactants and small solid particles. The oil recovery from the oil sludge is valuable, but the demulsification by using regular demulsifiers could be hindered by the solids. Therefore, the solid separation is important for oil recovery. In this paper, firstly, properties of heavy oil sludge produced from the Liaohe Oilfield were analyzed. Then, a multistage chemical treatment was proposed and chemicals were screened for solid separation. Limonene, sodium sulphate solution, (dioctadecyl dimethyl ammonium bromide + citric acid) were chosen for different purposes at different stages, respectively. At last, the rational separation conditions were investigated. After the treatment, the solid content in oil decreased from 18.57% to be 0.9% by mass. In addition, the mixture of recovered oil and fresh crude oil can be dehydrated easily by using regular demulsifiers.

Biomonitoring of Benzene and Effect of Wearing Respirators during an Oil Spill Field Trial at Sea

The main aim of this study was to assess the biological uptake of benzene and polycyclic aromatic hydrocarbons (PAHs) for subjects exposed to fresh crude oil released at sea. The study included 22 subjects participating in an 'oil-on-water' field trial in the North Sea. Over 2 consecutive days, there were six releases with two different types of fresh crude oils. Exposed subjects (n = 17) were either located in small, open-air boats downwind and close to the released oil (<50 m) or on the main deck of two large vessels further from the released oil (100-200 m). Subjects assumed to be unexposed (n = 5) were located indoors on the command bridge of either vessel. Full-shift personal benzene exposure was monitored with passive thermal desorption tubes (ATD-tubes) packed with Tenax TA and subsequent gas chromatographic analysis. Urine samples were collected before and after work-shift on both days and analyzed for urinary markers of benzene [(S-phenylmercapturic acid (SPMA)] and PAHs [1-hydroxypyrene (1-OH)]. Information about the use of personal protective equipment, smoking habits, location, work tasks, and length of work-shift were recorded by a questionnaire. Subjects located in the small boats downwind and close to the released oil were exposed to relatively high concentrations of benzene (arithmetic mean = 0.2 ppm, range 0.002-1.5 ppm) compared to the occupational exposure limits (OELs) for 8 h (1 ppm) and 12 h (0.6 ppm). Although respirators were available to all exposed subjects, SPMA was detected in post-shift urine (0.5-3.3 µmol mol-1) of five exposed subjects reporting not wearing respirators, all located in the small boats downwind and close to the released oil. For exposed subjects wearing respirators (n = 12), the post-shift urinary SPMA was below the detection limit (0.8 µmol mol-1) even when the benzene exposure exceeded the OELs. Urinary levels of PAH were within the reference range of what is considered as background levels (<0.4 µmol mol-1). During the initial stages of a bulk oil spill at sea, when the evaporation of benzene is at its highest, it is important to use appropriate respirators to prevent biological uptake of benzene.

Effect of ionic strength on crude emulsification and EOR potential of micellar flood for oil recovery applications in high saline environment

Micellar flooding is one of the chemical oil recovery techniques in which micelle action emulsifies the crude oil to be mobilized in form of emulsion from a subsurface porous media. However, the subsurface conditions such as high ionic strength and temperature are challenges to the successful use of micellar flood owing to the deterioration of micelle action suggesting no crude emulsification. The ionic compounds dissociate into different ions that may further affect micelle action via loss in viscosity and pressure drop, increased water cut, and mobility contrast between micellar flood and displaced oil. Thus, investigation leading to the successful use of micellar flood, context to crude emulsion, in extreme salinity and temperature is vital to extend the use of chemical methods in new reservoirs. In this work, a typical surfactant sodium dodecyl sulfate (SDS) solution with critical micelle concentration (0.8 wt%) was tested to emulsify a fresh crude oil in the presence of varying ionic strength (0–4 wt%, NaCl/CaCl2 and temperature (40–98 °C). The efficacy of SDS micelles to produce crude emulsion significantly reduced with increasing salt concentration as reported through microscopic, rheological, and flooding experiments, particularly for divalent salt (CaCl2) than monovalent salt (NaCl). The increase in temperature (>40 °C) further curtailed the growth of crude emulsion, mainly due to enhanced droplet coalescence; thus the use of micellar flood is critical in a reservoir enriched with high salinity and high temperature. Salinity effect on emulsion viscosity is reported through rheological measurements. The study highlighted important aspects of surfactant flooding and is a forward step towards the use of SDS based micellar flood at complex reservoir conditions.

FITOTOXICIDAD DE UN SUELO CONTAMINADO CON PETRÓLEO FRESCO SOBRE Phaseolus vulgaris L. (LEGUMINOSAE)

Se evaluaron los efectos toxicos que produce un suelo contaminado con petroleo fresco sobre plantas de Phaseolus vulgaris . Para ello se genero un indice absoluto de fitotoxicidad que integra siete parametros, medidos a traves de indices relativos de fitotoxicidad para las variables: altura, longitud radical, numero de nodulos y biomasa seca (foliar, radical, del fruto y total). Asimismo, se calcularon los coeficientes de determinacion (R 2 ). El bioensayo se realizo bajo condiciones de tunel de plastico y se evaluo los efectos toxicos del petroleo en plantas de frijol negro ( P. vulgaris L.) al cabo de 100 dias. Se establecio un diseno experimental de bloques al azar en condiciones semicontroladas, con seis tratamientos con tres repeticiones por tratamiento. Las concentraciones de hidrocarburos fueron: 1500, 3000, 4500, 6000, 7500 y 9000 mg/kg de hidrocarburos totales del petroleo (HTP) y un tratamiento testigo (0 mg/kg).Al dia 100, el detrimento fisiologico [emergencia (R 2 = 0.89; b = -3.427); altura(R 2 = 0.84; b = -0.0029); longitud radical (R 2 = 0.62; b = -0.001); numero de nodulos (R 2 = 0.68; b = -0.0092) y biomasa total (R 2 = 0.77; b = -0.0014)] de las plantas mostro una correlacion negativa con la concentracion de los HTP en el suelo, con diferencias entre los tratamientos (Tukey p≤ 0.05). Al dia 68 del ensayo se observo marchitez de las plantas a concentraciones mayores de 3000 mg/kg HTP.

Oil Spill Field Trial at Sea: Measurements of Benzene Exposure

Characterize personal exposure to airborne hydrocarbons, particularly carcinogenic benzene, during spill of two different fresh crude oils at sea. The study included 22 participants taking part in an «oil on water» field trial in the North Sea. Two types of fresh crude oils (light and heavy) were released six times over two consecutive days followed by different oil spill response methods. The participants were distributed on five boats; three open sampling boats (A, B, and C), one release ship (RS), and one oil recovery (OR) vessel. Assumed personal exposure was assessed a priori, assuming high exposure downwind and close to the oil slick (sampling boats), low exposure further downwind (100-200 m) and upwind from the oil slick (main deck of RS and OR vessel), and background exposure indoors (bridge of RS/OR vessel). Continuous measurements of total volatile organic compounds in isobutylene equivalents were performed with photoionization detectors placed in all five boats. Full-shift personal exposure to benzene, toluene, ethylbenzene, xylenes, naphthalene, and n-hexane was measured with passive thermal desorption tubes. Personal measurements of benzene, averaged over the respective sample duration, on Day 1 showed that participants in the sampling boats (A, B, and C) located downwind and close to the oil slick were highest exposed (0.14-0.59 ppm), followed by participants on the RS main deck (0.02-0.10 ppm) and on the bridge (0.004-0.03 ppm). On Day 2, participants in sampling boat A had high benzene exposure (0.87-1.52 ppm) compared to participants in sampling boat B (0.01-0.02 ppm), on the ships (0.06-0.10 ppm), and on the bridge (0.004-0.01 ppm). Overall, the participants in the sampling boats had the highest exposure to all of the compounds measured. The light crude oil yielded a five times higher concentration of total volatile organic compounds in air in the sampling boats (max 510 ppm) than the heavy crude oil (max 100 ppm) but rapidly declined to <20 ppm within 24 min after release of oil, indicating short periods of exposure. The personal exposure to benzene downwind and close to the oil slick during spills of light crude oil was relatively high, with concentration levels approaching the occupational exposure limits for several participants. For bulk spill scenarios like in this study, cleanup should not be initiated the first 30-60 min to allow for evaporation, while appropriate personal protective equipment should be used in continuous spills when working downwind and close to the oil slick.

Crude Oil Effects on Redox Status of Salt Marsh Soil in Louisiana

Core Ideas Crude oil did not lower redox status of wetland soil. Crude oil delayed return to aerobic threshold after draining. Oil in marsh soil can depress redox during low water events. In 2010, the Deepwater Horizon (DWH) oil spill triggered extensive research on crude oil impacts on flora and fauna of the Gulf of Mexico. Little research has investigated impact of spilled oil on redox condition of wetland soil. Redox condition is an excellent proxy for oxygen levels, which control biogeochemical functions linked to valuable ecosystem services. The goal of this study was to quantify effects of crude oil on wetland soil redox conditions in cores collected from a salt marsh in Barataria Bay, LA. Treatments tested were nonoiled control, weathered crude oil at the soil surface, fresh crude oil at the soil surface, and a layer of buried weathered crude oil 5 cm beneath the soil surface to mimic the presence of buried oil found in marshes. No significant differences in redox potentials were detected among treatments at any depth at the end of the 35‐d flooded, anaerobic study. After drainage of the cores began, redox was measured to the time to reach the aerobic threshold (+300 mV) within the rhizosphere. Mean redox values for control cores reached +300 mV after 193 h. Both fresh and weathered crude oil surface treatments reached +300 mV after 316 h while the buried crude oil treatment reached the aerobic threshold after 370 h. These results suggest the presence and location of crude oil in the soil profile can impact soil redox conditions which could alter biogeochemical processes over the long term and induce oxygen stress on wetland vegetation and organisms in the soil.

Thermal Properties and Burning Efficiencies of Crude Oils and Refined Fuel Oil

ABSTRACT The thermal properties and burning efficiencies of fresh and weathered crude oils and a refined fuel oil were studied in order to improve the available input data for field ignition systems for the in-situ burning of crude oil on water. The time to ignition, surface temperature upon ignition, heat release rate, burning rate and burning efficiency of two fresh crude oils (DUC, a light crude and Grane, a heavy crude), one fresh refined fuel oil (IFO 180) and weathered DUC (30–40 wt% evaporated and 40 wt% evaporated with 40 vol% water) were tested. Experiments were conducted in a newly designed water-cooled holder for a cone calorimeter under incident heat fluxes of 0, 5, 10, 20, 30, 40 and 50 kW/m2. The results clearly showed that the weathered oils were the hardest to ignite, with increased ignition times and critical heat fluxes of 5–10 kW/m2. Evaporation and emulsification were shown to be the determining factors increasing the critical heat flux compared to the physical properties of the oils. Boilover was observed for both emulsified DUC and fresh Grane and dominated the energy released by these oils. These results provided further evidence that the boilover phenomenon is correlated to the superheating of relatively volatile components such as water (DUC emulsion) or light hydrocarbons (Grane). Boilovers can thus occur due to inherent properties of the burning oil and should therefore be taken into account in the safety planning of in-situ burning operations. Maximum burning efficiencies of 85–90% were obtained for heat fluxes of 40–50 kW/m2 for the crude oils and 80% at 30 kW/m2 for IFO 180. The heat feedback in large scale fires, however, was estimated to be about 17 kW/m2, for which the burning efficiencies were &amp;lt; 80%. These results indicate that the increased heat feedback to the fuel surface is not the only factor that increases the burning efficiency for large scale fires compared to laboratory experiments. Additional factors such as feeding of surrounding oil into the fire by buoyancy induced wind flows into the hot smoke plume are probably also contributing to these increased burning efficiencies.

Phototoxic potential of undispersed and dispersed fresh and weathered Macondo crude oils to Gulf of Mexico Marine Organisms.

Crude oils contain a mixture of hydrocarbons, including phototoxic polycyclic aromatic hydrocarbons (PAHs) that have the ability to absorb ultraviolet (UV) light. Absorption of UV light by PAHs can substantially increase their toxicity to marine organisms. The objective of the present study was to examine the potential for phototoxicity of fresh and naturally weathered Macondo crude oils alone and in combination with the dispersant Corexit 9500 to mysid shrimp (Americamysis bahia), inland silverside (Menidia beryllina), sheepshead minnow (Cyprinodon variegatus), and Gulf killifish (Fundulus grandis). Acute toxicity tests were conducted using combinations of natural or artificial sunlight and low-energy water-accommodated fractions (WAFs) of fresh and weathered Macondo crude oils collected from the Gulf of Mexico. Studies were also conducted to compare the phototoxicity resulting from natural and artificial sunlight. Fresh Macondo crude oil was more phototoxic than weathered crude oils, both in the presence and in the absence of UV light. Differences in toxicity between fresh and weathered crude oils were likely attributed to lighter-ringed PAHs in fresh crude oils. Phototoxic PAHs were relatively resistant to weathering compared with lighter-ringed PAHs. The addition of Corexit 9500 to crude oil increased toxicity compared with tests with crude oil alone, by increasing phototoxic PAH concentrations in WAFs. Macondo crude oils had the potential to be phototoxic to Gulf of Mexico marine organisms if specific light conditions and PAH concentrations were present during the Deepwater Horizon oil spill. Environ Toxicol Chem 2017;36:2640-2650. © 2017 SETAC.