Oil Spill Dispersants Research Articles

Optimization and Performance Test of Oil Spill Dispersant at Bioremediation of Contaminated Soil with Heavy Oil by Bioslurry Technique

Petroleum industry activities produce waste such as petroleum hydrocarbons which damage to the soil environment due to changes in soil physical, chemical and biological properties. Oil Spill Dispersant (OSD) is a product that can break down waste of oil into small parts so that it can be dispersed naturally. Laboratory experiments aimed to find out optimize and performance test of OSD in the process of bioremediation with using bio-slurry technique on contaminated soil with heavy oil was carried out at Laboratory of Surfactant and Bio-energy Research Center (SBRC), Research and Community Service Institute of Bogor Agricultural University on January - August 2018 using contaminated soil with heavy oil. The experiment used Response Surface Method (RSM) with two factors, namely the incubation time factor (X1) and the Dispersant to oil ratio (DOR) (X2). The observed variables were soil Total Petroleum Hydrocarbons (TPH), pH, total microbes, and Chemical Oxygen Demand (COD) at soil solution. The results showed that the treatment of incubation time and its combination with DOR significantly reduced soil TPH, increased soil acidity, and increased soil total B. megaterium, but did not significantly affect on COD in soil solutions. Optimization of OSD with RSM showed that the higher DOR of OSD and the longer the incubation time, the higher also the rate of biodegradation of TPH. The optimum conditions were reached at DOR of 1.16:1 and incubation time of 7 days which were able to degrade soil TPH of 54.30%. The optimum conditions of soil pH (8.825) was reached at DOR of 1:1 and incubation time of 5 days, as well as the optimum conditions of B. megaterium (8.35 log CFU g-1) was reached at DOR of 0.86:1 and incubation time of 7 days. Oil spill dispersant (OSD) increased COD in soil solution in both uncontaminated and contaminated soils with heavy oil.

Stability of mechanically and chemically dispersed oil: Effect of particle types on oil dispersion.

Oil spill dispersant (OSD) application is one of the preferred cleanup options to cope with oil spills at sea. OSD, in principle, can enhance biodegradation of oil because of its effectiveness in producing relatively small droplets and dispersing them into the water column. Under turbulent conditions, suspended particulate matter (SPM) which are present naturally in the environment can interact with oil to form aggregates known as oil-SPM aggregates (OSA) which also enhances biodegradation of oil. Despite its high dispersion effectiveness, chemically dispersed oil (CDO) has a tendency to resurface with increasing time which decreases the biodegradation potential. Meanwhile, the presence of SPM prevents recoalescence of dispersed oil which can enhance stability of oil droplets. This study focused on the effects of SPM on the dispersion effectiveness and stability of mechanically dispersed oil (MDO) and CDO. Dispersion tests of MDO and CDO extended to 72h with and without SPM to see the initial effectiveness and the prolonged stability of dispersed oil. In the presence of SPM, the oil dispersed by MDO increased by 14.8-40.7%, while the resurfacing oil by CDO decreased by 8.7-19.4%. Regardless of SPM type, oil dispersion effectiveness and stability of MDO and CDO were significantly increased. Long-term stability test for 3months showed that stability of OSA increased as the particle size decreased and particle counts increased.

Molecular characterization of nonionic surfactant components of the Corexit® 9500 oil spill dispersant by high-resolution mass spectrometry.

Approximately 7 million liters of Corexit® dispersants were applied during the 2010 Deepwater Horizon oil spill to facilitate the dispersion of crude oil. At the time of application, the exact chemical composition of Corexit® was relatively unknown. Characterization of Corexit® 9500 was performed using high-resolution mass spectrometry to further understand the complexity of the nonionic surfactant components of this mixture. Corexit®9500 was analyzed by ultra-high-performance liquid chromatography (UHPLC) coupled to a high resolution Orbitrap Fusion Lumos mass spectrometer operated in positive electrospray ionization mode and a charged aerosol detector. Chromatographic conditions were optimized to efficiently separate isobaric and isomeric compounds. Polyethoxylated nonionic surfactants in Corexit® 9500 were identified using the following criteria: accurate mass (<3 ppm), retention time, and homologue series; in addition, interpretation of high-resolution tandem mass spectra was used to annotate tentative component structures. More than 2000 polysorbate nonionic surfactants in 87 homologue series were detected. Polysorbate surfactants were characterized by the type of molecular basis group (sorbitan, isosorbide, or fatty acid), degree of esterification (n= 0-4), ester chain length (C6-C24), and ester saturation, in addition to polydispersion by ethoxylation. Isomeric compounds were differentiated by LC/HRMS/MS analysis with product ion assignment. Results from the charged aerosol detector showed that the diesters (23.9 ± 0.78%) were the most abundant component in Corexit® 9500 followed by dioctyl sodium sulfosuccinate (DOSS) (19.2 ± 1.5%), triesters (17.3 ± 1.5%), and monoesters (15.7 ± 2.3%). Our analytical approach facilitated the characterization of polysorbate surfactants within Corexit® 9500 and allowed a systematic study to differentiate isomeric and isobaric compounds, when standards were not available. The characterized composition of Corexit® 9500 will facilitate future studies to determine the chemical and biological transformation kinetics and byproducts of Corexit® 9500 under environmental conditions.

Interfacial Phenomena of Natural Dispersants for Crude Oil Spills.

A natural surfactant was studied to simulate the dispersion process of crude oil in water. The interfacial phenomena of this natural dispersant was compared with a commercially available chemical dispersant, COREXIT EC9500A. This functional surfactant was extracted from the mucilage of the Opuntia ficus-indica cactus species. The evaluation to determine the efficacy to disperse crude oil of the cactus-based mucilage extract (nongelling extract, NE) was based on characterizing surface and interfacial tension, dispersion efficiency, mixing effects, salinity effects, stability, and droplets size distributions. We found that surface tension values follow a linear relationship with respect to the natural logarithm of the concentrations of NE. The application of NE in the water phase led to decreasing oil/water interfacial tensions. Surface tension tests were also used to quantify the effect of oil-in-water (O/W) emulsion ratios once either natural or commercialized dispersants were added. A key finding of our work is that the surface tension between typical 6% and 3% v/v O/W emulsions was significantly reduced with the addition of discrete amounts of NE. This result indicated that the dynamic balance between O/W and water-in-oil (W/O) emulsions was thermodynamically more stable toward O/W emulsion states with NE. We also found that O/W emulsions with higher dispersion effectiveness were formed for both 10 and 35 practical salinity units, as the dispersant to oil ratios increased, with a significant correlation to the mixing energy. We observed that the O/W emulsions with natural dispersants had a significantly smaller weighted average diameter compared to those with COREXIT EC9500A. Such a phenomenon can be explained by understanding intermolecular interactions due to the structure and type of dispersant. In conclusion, cactus-based mucilage extracts could be used as environmentally benign dispersants and, therefore, reduce negative social perceptions of the application of dispersants to clean up spilled oil.

Hydrophilic-Lipophilic-Difference (HLD) Guided Formulation of Oil Spill Dispersants with Biobased Surfactants

Abstract The large-scale use of dispersants during the BP Horizon spill revealed various risks associated with these formulations, particularly the use of volatile organic compound (VOC) solvents linked to respiratory illnesses, and the poor biodegradability of surfactants. Previous attempts at solving these issues involved formulations of lecithin and polyethylene glycol ester of sorbitan monooleate (Tween® 80) that still required the use of a volatile solvent, ethanol. In this work, the Hydrophilic-Lipophilic Difference (HLD) framework was used to develop a lecithin formulation containing food-grade lipophilic (Glycerol MonoOleate – GMO- and sorbitan monooleate – Span® 80) and hydrophilic (polyglycerol caprylate) linkers in combination with a nonvolatile and mineral oil solvent with food additive status. The HLD parameters for lecithin, linkers, and oils were used to determine the lecithin-linker formulas that yielded HLD ∼0 (the surfactant phase inversion point), reaching interfacial tensions of 10−2 mN/m, and high emulsification effectiveness with diluted bitumen. This effectiveness was close to that obtained with a simulated dispersant, and superior to the lecithin-Tween® 80-ethanol formula. The lecithin-linker system produced 4–11 μm emulsified drops, sufficiently small to enhance the biodegradability of the dispersion.

Amphiphilic Janus particles for efficient dispersion of oil contaminants in seawater

Application of dispersants is one of the widely used oil spill response strategies. With the growing concern for particulate emulsifiers, applying amphiphilic Janus particles to emulsify oil in seawater has been examined in this paper. Amphiphilic Janus particles with a combination of colloidal particles and amphiphilic characteristic are found to show a highly effective emulsification for various oils in seawater and overcome several drawbacks of conventional chemical dispersants. We report the synthesis of amphiphilic Janus silica particles (JSPs) as a novel oil spill dispersant and confirm their amphiphilicity by various techniques. The oil-in-seawater emulsion stabilized by JSPs presents small and stable oil droplets in one month, even at a higher volume ratio of oil to seawater and a wide temperature range. It is believed that the small size and high stability of droplets are very important to oil dispersion and eventual biodegradation. Through confocal laser scanning microscopy and scanning electron microscope observations, JSPs were found to anchor tightly at droplet surface and form a dense interfacial particle film to prevent droplets coalescence. The appropriate wettability of JSPs and the reduced interfacial tension contribute to the high interfacial adsorption energy of JSPs. Additionally, JSPs show weak inhibitory effect on oil-degrading bacteria, which is confirmed by bacterial growth curve, resazurin test and oil biodegradation experiment. This study reveals that amphiphilic Janus silica particles hold an impressive capability for environmentally friendly treatment of oil spills.

Comparative Bioremediation Potentials of Pseudomonas aeruginosa KX828570 and Bacillus megaterium KY085976 on Polluted Terrestrial Soil Treated with Oil Spill dispersant

Aim: To assess the bioremediation potential of Pseudomonas aeruginosa and Bacillus megaterium on oil spill dispersant polluted terrestrial soil.&#x0D; Study Design: The study employs experimental design, statistical analysis of data and interpretation.&#x0D; Place and Duration of the Study: Polluted Terrestrial Soil (Ts) samples were collected from Kegbara-Dere community in Gokana Local Government Area of Rivers State with sterile shovel from three different spots at the same location and put in black polythene bags and transported to the microbiological laboratory within 24 hours for physicochemical and microbiological analyses. Oil spill dispersant (OSD/LT and OSD/Seacare) were obtained from Baker and Hughes Nigeria Limited in Rivers state, Nigeria.&#x0D; Methodology: Standard microbiological procedures were used to enumerate, isolate and identify the bacterial isolates. Pseudomonas aeruginosa and Bacillus megaterium in oil spill dispersants contaminated soil were monitored over a period of 1, 7, 14, 21 and 28 days respectively for their bioremediation potentials.&#x0D; Results: The presence of Pseudomonas aeruginosa (Pa) or Bacillus megaterium(Bm) in oil spill dispersant polluted soils enhanced decrease in Total Hydrocarbon Content (THC) of the soil. THC for control soil reduced from 18348.68 mg/kg to 9111.84 mg/kg; TS+OSD/LT+Bm, 18348.68 to 7092.11 mg/kg; TS+OSD/LT+Pa, 18348.68 to 6263.16(mg/kg); TS+OSD/LT+Bm+Pa, 18348.68 to 2473.68 mg/kg; TS+OSD/SC+Bm, 18348.68 to 6421.05 mg/kg; TS+OSD/SC+Pa, 18348.68 to 5618.42 mg/kg; TS+OSD/SC+Bm+Pa, 18348.68 to 5835.53 mg/kg, between the first (day 1 ) and last day ( day 28). The percentage (%) bioremediation rate of polluted soil was as follows: control (TS(CRTL) 50.3%, TS+OSD/LT+Bm 61.3%, OSD/LT+Pa 65.9%, and OSD/LT+Bm+Pa 86.5% Whereas, TS+OSD/Seacare+Bm had 65.0%, OSD/Seacare+Pa 69.4%, OSD/Seacare+Bm+Pa 68.2% respectively. The highest percentages of THC in this study were from soil samples treated with oil spill dispersant and organisms while the least was observed in treatments without oil spill dispersant and organism. This suggests that microorganisms are more abundant in oil spill dispersant polluted soils than unpolluted soils.&#x0D; Conclusion: From this study, it was observed that bioremediation of dispersant polluted environments could be achieved by stimulation of native microorganisms such as Pseudomonas aeruginosa KX828570 and Bacillus megaterium KY085976 and this would be cost effective in the clean-up strategy for such pollutants.

Improved oil spill dispersant monitoring in seawater using dual tracers: Dioctyl and monoctyl sulfosuccinates sourced from corexit EC9500A

A high resolution mass spectrometry method was developed for the environmental impact monitoring of oil spill dispersants. Previously reported instability of dioctyl sulfosuccinate (DOSS) dispersant tracer was addressed by the new procedure. The method monitors both DOSS and its degradation product, monooctyl sulfosuccinate (MOSS), by liquid chromatography time-of-flight mass spectrometry. The related isomer, 4-(2-ethylhexyl) 2-sulfobutanedioate, was chromatographically resolved from MOSS but was not a product of DOSS degradation. Using this direct injection method (10 μL), the practical lower limit of quantitation was 0.5 nM for each analyte, a concentration equivalent to 0.22 ng mL−1, or 0.30 ng mL−1 including initial dilution factor with acetonitrile. The method was shown applicable to analysis of the dispersants Corexit® EC9500 A, Finasol OSR 52, Slickgone NS, and Slickgone EW for which DOSS is an active ingredient. A marine microcosm study of Corexit EC9500A, together with diluted bitumen (dilbit), at 15 ± 1 °C, provided evidence of the stoichiometric conversion of DOSS to MOSS under conditions reflecting a western Canadian marine environment. The advantage of the developed method is in its ability to extend environmental seawater sample collection time from 4 days for DOSS alone, to 14 days when both DOSS and MOSS are simultaneously analysed and results combined. The collection time is likely extended beyond the 14 day period with cooler temperatures. Preservation of collected seawater samples using sodium hydroxide, converting DOSS into MOSS in situ, was rejected due to stability issues. Addition of disodium ethylenediaminetetraacetic acid did not improve hold times, thus eliminating the theory of cation induced micelle effects causing DOSS loss.

The effectiveness of oil spill dispersant addition for phytoremediation of petroleum-contaminated soil using Ricinus communis L

Phytoremediation is one of the most effective and environmental-friendly methods in retrieving oil-contaminated soil. The decline of Total Petroleum Hydrocarbon (TPH) oil in the phytoremediation process will be accelerated by Oil Spill Dispersant (OSD) as a surfactant and the use of Ricinus communis L. plant. Commercial OSD products used in the remediation process are S200 OSD which contains LAS surfactant, which is a US EPA recommendation and is known to be less environmental-friendly, so SBRC-IPB develops OSD containing palm oil surfactants and is environmental-friendly. The purpose of this study was to determine the performance of OSD and R . communis to reduce TPH. This study used a completely randomized design with two factors, namely OSD and plant use. The results of this study indicated that OSD from SBRC-IPB improved plant growth, increased dry plant biomass, accelerated the decrease in TPH and increased the bacterial population compared to the S200 OSD and control. The combination of OSD from SBRC and R . communis was able to degrade TPH better than S200 OSD, with and without R . communis, with TPH concentrations of 30,000 ppm (3%) to 2,333 ppm (0.2%) for 20 weeks. This showed that the use of OSD was able to provide a positive response in the phytoremediation process of land contaminated with petroleum

Bioremediation Potential of Pseudomonas aeruginosa KX828570 on Crude Oil Spill Polluted Marshland and Terrestrial Soil Treated with Oil Spill Dispersant

Aim: To investigate bioremediation potentiality of Pseudomonas aeruginosa KX828570 on crude oil Polluted Marshland and Terrestrial Soil treated with oil spill dispersant&#x0D; Study Design: The study employs experimental design, statistical analysis of data and interpretation.&#x0D; Place and Duration of the Study: Soil samples were collected from K-Dere, Gokana L.G.A, and were transported to the Microbiology Laboratory of Rivers State University, Port Harcourt, Nigeria for analyses while Oil spill dispersant (OSD/LT and OSD/Seacare) were from Barker and Hughes Nig Ltd (formally mil park Nigeria limited), all in Rivers state, Nigeria. This investigation study lasted for 28 days and sampling was done every 7day period.&#x0D; Methodology: Eight experimental set up were carried out using Pseudomonas aeruginosa KX828570 as the bio-augmenting organism in terrestrial and marshland soil contaminated with two Oil spill dispersant (OSD/LT and OSD/Seacare) separately. Controls for the two soil types were made without organism and treatment. Its bioremediation potential on the pollutants and two types of soil were monitored for 28 days. The setup was tilled twice a week to provide moisture and more oxygen for the organisms to thrive. Analysis of pH, Temperature, Moisture content, Total Hydrocarbon Content, Total Heterotrophic Bacteria, Dispersant Utilizing Bacteria was carried out at weekly intervals.&#x0D; Results: The pH of both soils ranged from 5.75 to 7.37; temperature from 270C to 340C; moisture content 03 to 0.6 across the soil samples. Total Hydrocarbon Content (THC) showed a steady decline from day 1 – 28. The percentage (%) bioremediation rates of polluted soils were as follows: Terrestrial soil+OSD/Seacare+Pseudomonas aeruginosa KX828570 69.4% &gt; Terrestrial soil+OSD/LT+ Pseudomonas aeruginosa KX828570 65.9% &gt; Marshland soil+OSD/Seacare+ Pseudomonas aeruginosa KX828570 52.6% &gt; Marshland soil+OSD/Seacare+ Pseudomonas aeruginosa KX828570 47.6%. Dispersant utilizing bacterial count in marshland and terrestrial soil ranged from 6.013 to 7.338 log10Cfu/g and 6.045 to 7.301 log10Cfu/g respectively from Day 1 to 28.&#x0D; Conclusion: From the investigation, it revealed that Oil spill dispersants are more degradable in terrestrial soil than marshland soil. OSD/Seacare is more biodegradable than OSD/LT in both terrestrial and marshland soil augmented with Pseudomonas aeruginosa KX828570. Thus, Pseudomonas aeruginosa KX828570 have been found to be a potential bioremediation agent in oil spill dispersant polluted marshland and terrestrial soil.

Biosurfactant-modified palygorskite clay as solid-stabilizers for effective oil spill dispersion

An effective and conventional remediation technique in marine oil spills is to apply chemical dispersants to emulsify oil slicks into small oil droplets. Still, the potential hazards of chemical dispersants onto the marine ecosystem have motivated the research for environmentally friendly alternative while keeping exceptional dispersion ability. Here, we showed that the mixture of palygorskite (PAL) and rhamnolipid (Rha) formed a biocompatible alternative to synthetic surfactants used for oil spill dispersion. The oil droplets dispersed by R-PAL presented a small average size and long-term stability, which illustrated the synergistic interactions between Rha and PAL acting as an efficient dispersant in artificial sea water (ASW). Due to the strong flocculation caused by high salinity, PAL alone was not effective emulsifiers in ASW. A small amount of Rha could played a major role in modifying the surface characteristics of PAL and decreasing oil-water interfacial tension. Therefore, PAL particles irreversibly adsorbed onto the oil-ASW interface and formed a rigid interfacial film around oil droplets in the presence of Rha, which offered an efficient barrier to droplet coalescence. The synergistic interactions between PAL and Rha could enable the dispersion of tetradecane in ASW. Such a functionality was further tested in dispersing crude oil in ASW. The study presents a new strategy of using a mixture of PAL and Rha for oil dispersion, thus providing an ecofriendly alternative to conventional dispersants.

A binary mixture of a biosurfactant and an ionic liquid surfactant as a green dispersant for oil spill remediation

Formulations based on conventional surfactants and organic solvents have been used as potential dispersants for oil-spill remediation. However, their toxicity restricts their usage in marine environments. As a low-toxicity alternative, in this article we report an oil dispersant based on a binary mixture of an ionic liquid surfactant, choline laurate ([Cho][Lau]), and a biosurfactant, lactonic sophorolipid. We investigated the micellar properties, including the critical micelle concentration, micellar interaction parameter (β), and activity coefficients (f1 and f2) for the mixed surfactant system. A non-ideal and synergistic interaction between [Cho][Lau] and lactonic sophorolipid was observed. A stable oil-in-water emulsion formed at an optimal ratio of 40:60 (w/w) of [Cho][Lau] and lactonic sophorolipid. At this ratio, a dispersion effectiveness of 83% was achieved with a dispersant-to-oil ratio of 1:25 (v/v). We observed the dispersed oil droplets with an optical microscope and evaluated their size using dynamic light scattering. The droplet size decreased with increasing dispersant-to-oil ratio. We also assessed the toxicity of the binary surfactant mixture in zebra fish (Danio rerio). Based on this assessment, the mixture can be classified as non-toxic. Therefore, the mixture of [Cho][Lau] and lactonic sophorolipid is a potential alternative to conventional toxic oil-spill dispersants.

Bioremediation Potential of Aspergillus clavatus and Pichia spp. on Oil Spill Dispersant Polluted Marshland

Bioremediation Potential of Aspergillus clavatus and Pichia spp. on Oil Spill Dispersant Polluted Marshland

An Operational Marine Oil Spill Forecasting Tool for the Management of Emergencies in the Italian Seas

Oil extraction platforms are potential sources of oil spills. For this reason, an oil spill forecasting system was set up to support the management of emergencies from the oil fields in the Italian seas. The system provides ready-to-use products to the relevant response agencies and optimizes the anti-pollution resources by assessing hazards and risks related to this issue. The forecasting system covers seven working oil platforms in the Sicily Channel and middle/low Adriatic Sea. It is composed of a numerical chain involving nested ocean models from regional to coastal spatial scales and an oil spill model. The system provides two online services, one automatic and a second dedicated to possible real emergencies or exercises on risk preparedness and responding. The automatic service produces daily short-term simulations of hypothetical oil spill dispersion, transport, and weathering processes from each extraction platform. Products, i.e., risk maps, animations, and a properly called bulletin, are available on a dedicated web-portal. The hazard estimations are computed by performing geo-statistical analysis on the daily forecasts database. The second service is activated in near-real-time producing oil spill simulations for the following 48 h.

Investigation of choline based ionic liquids as an oil spill dispersant

Chemical dispersants are universally used to overcome oil spill damages. However, the toxicity related with chemical dispersants minimizes its usage as oil spill dispersants. Thus, the employment of biodegradable and environmental benign dispersants in marine environment is much needed. In this research, the capability of choline myristate [Cho][Myr] and choline oleate [Cho][Ol] were investigated to be used as oil spill dispersants. Results reported in this study illustrates that by combining these two amphiphilies, an effective dispersion is achieved. A maximum dispersion of 71 % was achieved by combining [Cho][Myr] and [Cho][Ol] with an optimal ratio of 60:40 (w/w). The dispersant to oil ratio (DOR) was 1:10 (v/v) at this optimal combination. Further, by increasing the DOR the effectiveness increases and about 78% dispersion is achieved at 1:1 (v/v). Moreover, the blend of [Cho][Myr] and [Cho][Ol] at 60:40 (w/w) ratio formed a stable emulsion than its single components.

Phenomenological Model of Natural Dispersion of an Oil Spill in the Sea and Some Associated Parameterization Processes

The paper proposes a new parameterization of natural dispersion of a marine oil spill due to wind-wave breakup of the oil slick and penetration of oil droplets into the water. The quantity of oil returning to the surface due to positive buoyancy in the time between wind wave overturns is estimated. The role of vertical turbulent exchange as a factor limiting oil droplet flux from the sea surface into the water column is discussed.

Critical review and analysis of aquatic toxicity data on oil spill dispersants.

Oil spill response requires consideration of several countermeasures including chemical dispersants, but their potential toxicity to aquatic species poses a concern. Considerable in vivo aquatic toxicity data from laboratory exposures have been generated since 2010 for current-use dispersants. The objective of the present review is to provide a synthesis of these data to improve dispersant hazard assessments. Data from multiple studies were evaluated based on reliability criteria. Although procedures, standards, endpoints, and statistical approaches were usually described, nearly a quarter of sources did not provide sufficient information to judge study quality but were considered on a case-by-case basis. Data were used to develop dispersant-specific species sensitivity distributions and hazard concentrations protective of 95% of the species (HC5). Given data limitations, post-2010 toxicity data were augmented with pre-2010 data and model predictions. The HC5s calculated for 54 dispersants fell mostly within the moderate to slightly toxic range and were compared to field dispersant-only concentrations estimated from operational application rates under conservative assumptions. Based on available evidence, dispersants may not pose a significant risk under field conditions to most aquatic species, if proper application and dilution are taken into account. Recommendations on improved toxicity testing and reporting as well as research needs are also provided. Environ Toxicol Chem 2018;37:2989-3001. © 2018 SETAC.

Biodegradation of oil spill dispersant surfactants in cold seawater

While biodegradation of chemically dispersed oil has been well documented, only a few studies have focused on the degradation of the dispersant compounds themselves. The objective of this study was to determine the biodegradation of dispersant surfactants in cold seawater, relevant for deep sea or Arctic conditions. Biotransformation of the surfactants dioctyl-sodium sulfosuccinate (DOSS), Tween 80, Tween 85, and α/β-ethylhexylsulfosuccinate (EHSS, expected DOSS hydrolysis product) in the commercial dispersants Corexit 9500, Dasic Slickgone NS and Finasol OSR52 were determined. The biotransformation studies of the surfactants were performed in natural seawater at 5 °C over a period of 54 days without oil present. The surfactants were tested at concentrations of 1, 5, and 50 mg/L, the lower concentration being as close as possible to expected field concentrations. Experiments with dispersants concentrations of 1 mg/L resulted in rapid biotransformation of Tween 80 and Tween 85, with depletion after 8 days, while DOSS showed rapid biotransformation after a lag period of 16 days. The degradation half-life of DOSS increased from 4.1 days to >500 days as Corexit 9500 concentrations went from 1 mg/L to 50 mg/L, emphasizing the importance of performing experiments at dispersant concentrations as close as possible to environmentally relevant concentrations. EHSS showed limited degradation compared to other surfactants. This study shows that the surfactants DOSS, Tween 80 and Tween 85 in the three chemical dispersants studied are biodegradable in cold seawater, particularly in environmentally relevant concentrations.

Microstructural characteristics of surfactant assembly into a gel-like mesophase for application as an oil spill dispersant

HypothesisPolyoxyethylene (20) sorbitan monooleate (Tween 80) can be incorporated into the gel-like phase formed by L-α-phosphatidylcholine (PC) and dioctyl sulfosuccinate sodium salt (DOSS) for potential application as a gel-like dispersant for oil spill treatment. Such gel-like dispersants offer advantages over existing liquid dispersants for mitigating oil spill impacts. ExperimentsCrude oil-in-saline water emulsions stabilized by the surfactant system were characterized by optical microscopy and turbidity measurements while interfacial tensions were measured by the spinning drop and pendant drop techniques. The microstructure of the gel-like surfactant mesophase was elucidated using small angle neutron scattering (SANS), cryo scanning electron microscopy (cryo-SEM), and 31P nuclear magnetic resonance (NMR) spectroscopy. FindingsThe gel-like phase consisting of PC, DOSS and Tween 80 is positively buoyant on water and breaks down on contact with floating crude oil layers to release the surfactant components. The surfactant mixture effectively lowers the crude oil-saline water interfacial tension to the 10−2 mN/m range, producing stable crude oil-in-saline water emulsions with an average droplet size of about 7.81 µm. Analysis of SANS, cryo-SEM and NMR spectroscopy data reveals that the gel-like mesophase has a lamellar microstructure that transition from rolled lamellar sheets to onion-like, multilamellar structures with increasing Tween 80 content.

Effects of oil spill response technologies on the physiological performance of the Arctic copepod Calanus glacialis

A mesocosm study with oil in ice was performed in Van Mijenfjorden in Svalbard to compare effects of the oil spill responses (OSR) in situ burning, chemical dispersion and natural attenuation on the physiological performance of the Arctic copepod Calanus glacialis. Seawater collected from the mesocosms in winter and spring was used in laboratory incubation experiments, where effects on fecal pellet production, egg production and hatching success were investigated over a period of 14 days. Polycyclic aromatic hydrocarbon (PAH) seawater concentrations were lowest in winter. Brine channel formation in spring resulted in an 18 times increase in PAH concentration in the chemical dispersion treatment (1.67 μg L−1), and a 3 fold increase in the natural attenuation (0.36 μg L−1) and in situ burning (0.04 μg L−1) treatments. The physiological performance of female C. glacialis was unaffected by the PAH seawater concentrations. However, a higher mortality and deformity of nauplii was observed in the chemical dispersion treatment, highlighting the importance of considering secondary effects on next generation in future environmental risk assessment of OSR. This study shows that during the ice-covered period, chemical dispersion of oil spills leads to higher PAH exposure than natural attenuation and in situ burning, with potential consequences for recruitment of Arctic copepods.