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Abstract
Mesocosm facilities consisting of five 3.5 m3 stainless steel tanks filled with seawater from the St Lawrence Estuary (Québec, Canada) were used to conduct a 2 month experiment under the natural conditions prevailing at the end of the winter in subarctic environments, with seawater temperatures ranging from -1.5°C (surface ice cover) to 3°C. Various oil treatments were simulated in mesocosms: Forties crude oil was chemically dispersed, adsorbed onto an immersed substrate and spilled without any treatment. Total oil concentrations ranged from

Abstract
Accidental spills and production lead to discharges of petroleum hydrocarbons and surface active agents to the sea. The Norwegian government has set guidelines adopted from the OSPAR commission for assessment and studies of the environmental load from these discharges. The free water masses are poorly studied compared to the benthic processes in this context and we question how oil and surfactants might bioaccumulate in a simplified marine pelagic food chain comprised of algae, crustaceans and fish. When test methods and species recommended for initial water based acute toxicity studies are to be implemented in more comprehensive studies like assessment of bioaccumulation various problems arose. An improvement of the OSPAR method for the production of Water Accommodated Fractions (WAFs) of oil is presented. Emphasis is on control of oil concentration and distribution in water, and on applicability for studies where larger volumes of WAF are required than for the demand in acute toxicity tests. Acute toxicity assessments of one oil, Blended Arabian Light topped at 150°C, and two non-ionic dispersants, hexactoxyparanonylphenol and a sophorolipid, were conducted on OSPAR recommended species. The toxicity responses were in line with observations made by others. At a given concentration the oil particle size during WAF preparation might influence subsequent expression of toxic effects. The same applied for the presence of emulsified oil particles in the WAFs where the organisms were exposed. Reasons for selecting other test organisms than those officially recommended for continued studies on bioaccumulation are presented and discussed

Abstract
In this study the author compares the effects of Ixtoc I crude and Corexit 9527 on the egg mortality of a fish species occurring in the Gulf of Mexico. Although the species used in this study - spot, Leiostomus xanthurus, is not important as a commercial food fish in the gulf, their early life history is similar to other more significant gulf sciaenids, e.g., Micropogonias undulates and Sciaenops ocellata. L. xanthurus spawn during the fall and early winter in nearshore ocean waters and produce floating eggs, 0.8 mm in diameter, which hatch in 48 h at 20 degree C

Abstract
The use of aircraft in the application of oil spill dispersants was shown to be a viable technique in 1979 when aerial spraying was used for the Mexican Pemex Ixtoc I oil spill and, more recently, at the Suffield, Alberta, aerially applied dispersant field trials (September 1980). The purpose of this paper is to present the results of a review of existing technical information about three specific component parts of the aerial spraying technique. The review identified parameters that affect the efficiency of aerial spraying that are useful in assessing practical operations. The analysis and reprt pertaining to the Suffield field trials (due January 1981) is currently being undertaken by the author and others and will be commented on in general terms only as the results pertain to this work

Abstract
The effective use of dispersants requires the addition of mixing energy to the oil slick after the application of the dispersant chemicals. This U.S. Environmental Protection Agency sponsored project was conducted at their OHMSETT testing facility to test the relative effectiveness of four devices for adding mixing energy to an oil slick under varied conditions. The four devices were: a five-bar gate, two fire-hose streams, a modified five-bar gate, and a small outboard motorboat. Tow speeds, wave conditions, and oil/water interfacial tension were varied. Underwater photography was used to record the depth of penetration of the oil droplets caused by the mixing devices at each test condition

Abstract
The Regional Response Teams in California, Oregon, and Washington have attempted to deal with the problem of providing rapid approval or denial of dispersant use requests during a major spill event. Realizing that the On-Scene Coordinator must act quickly in order for the dispersants to be effective, the RRT undertook a program to develop a system that would allow for approval or denial within four hours. The Regional Response Teams in Standard Federal Regions IX and X developed and implemented Dispersant Use Guidelines, from 1978 to the present, to enhance the regions capability to respond rapidly to requests for approval of dispersant use. The physical, chemical, and biological parameters associated with spilled oil and dispersants are evaluated in this procedure. A decision to use dispersants is based on balancing the possible contamination of the environment with other factors. Damages expected from spills not treated with dispersants are compared to damages which would be expected if the oil were successfully treated. The objective is to minimize the impact of spilled oil on natural resources. This paper summarizes the progress of two Regional Response teams in responding to the questions of dispersant use, reviewing dispersant guidelines, and recommending minimum standards for documentation. The procedure involves the interaction and cooperation of the several agencies, and promotes the timely use of knowledge and information

Abstract
Surfactants are of potential importance in the development of new techniques for enhanced oil recovery as well as for remediation of petroleum contaminated soils. With surfactant washing, 95% of the petroleum contaminants can be removed. As sorption dictates the reactions between a liquid and a solid, it is a decisive factor for the success of a remediation technique and for understanding the mechanisms which dictate transport and fate characteristics of contaminants in soils. The adsorption of surfactants from solution at the solid/liquid interface is a complex and imperfectly understood phenomenon. To investigate the nature of adsorption and desorption at the solid/liquid interface, a detailed experimental study was conducted using silica sand packs and clayey sand packs. Also, over twenty numerical simulation runs were conducted to model the phenomenon of surfactant adsorption and desorption. A simulation model based on surface excess concept was developed in this study. Numerical simulation results show excellent agreement with experimental results. This study showed that both salinity and clay can increase the adsorption level of surfactants. The role of surfactant concentration was studied. A higher concentration led to earlier surfactant breakthrough

Abstract
Chemical dispersants are used in oil spill response operations to enhance the dispersion of oil slicks at sea as small oil droplets in the water column. To be considered for use, the dispersants must be listed in the National Contingency Plan (NCP) Product Schedule. Since 1994, dispersants were required to pass an effectiveness test known as the Swirling Flask Test (SFT), which is described in Appendix C of 40 CRF 300. Listing of a dispersant on the NCP Product Schedule is contingent on the dispersant being at least 45% effective in dispersing South Louisiana crude (SLC) and Prudhoe Bay crude (PBC) oils as measured and calculated by the test. Shortly after adopting the SFT, the U.S. Environmental Protection Agency (EPA) began to receive complaints that the test was too rigorous and few dispersants that were previously listed on the NCP Product Schedule could achieve the 45% effectiveness criterion. Additionally, the SFT has been found to give widely varying results in the hands of different testing laboratories. A redesign of the test flask, which is characterized as being baffled with a stopcock at the bottom for undisturbed sample collection, is considered to be necessary to accomplish reproducibility within operators and between operators. This paper presents the development of a revised procedure for dispersant effectiveness testing called the Baffled Flask Test (BFT), and reports the reproducibility of the revised procedure by three independent operators. It also details the development of pass/fail selection criteria. Experimental results are presented comparing the repeatability of the SFT and BFT methods with three operators determining the effectiveness of 18 dispersants on SLC and PBC oils. Statistical analysis of the results indicated that the overall mean effectiveness of the SFT for all 18 dispersants was only 19.7% compared to 64.6% by the BFT and the coefficient of variation for the SFT was 21.9% versus only 7.8% for the BFT

Abstract
Chemical dispersants are used in oil spill response operations to enhance the dispersion of oil slicks at sea as small oil droplets in the water column. To assess the impacts of dispersant usage on oil spills, US EPA is developing a simulation model called the EPA Research Object-Oriented Oil Spill (ERO3S) model (http://www.epa.gov/athens/research/projects/eros/) and (Weaver, 2004). Due to the complexity of chemical and physical interactions between spilled oils, dispersants and the sea, an empirical approach to characterizing the interaction between the dispersant and oil slick may provide a useful or practical approach for including dispersant action in a model. The main objective of this research is to create a set of empirical data on three oils and two dispersants that has the potential for use as an input to the ERO3S model. These data are intended to give an indication of the amount of dispersal of these oils under certain conditions. The US EPA is developing an improved dispersant testing protocol, called the baffled flask test (BFT), which is a refinement of the swirling flask test (Venosa et al., 2002). Use of this protocol was the basis of the experiments conducted in this study. The variations in the effectiveness of dispersants caused by changes in oil composition, dispersant type, and the environmentally related variables of temperature, oil weathering, and rotational speed of the BFT were studied. The three oils tested were South Louisiana Crude Oil (SLC), an Alaska North Slope Crude (Prudhoe Bay Crude Oil, PBC), and Number 2 fuel oil (2FO). The two dispersants with the highest effectiveness scores under certain test conditions reported earlier were selected for this study. A factorial experimental design was conducted for each of the three oils for four factors: volatilization, dispersant type, temperature and flask speed. Each of the four factors was studied at three levels except for the dispersant factor where only two dispersants were considered. Statistical analysis of the experimental data was performed separately for the three oils. Empirical relationships between the amount of oil dispersed and the variables studied were developed. The experiments showed that dispersal increased with mixing energy/flask speed for each experiment performed, although there were cases with overlapping ranges of dispersal for different flask speeds. In these cases, increases in dispersal due to lack of weathering or increased temperature evidently accounted for the overlap. In about half of the experiments there was no significant relationship between weathering and dispersal. Where weathering was significant, it was inversely related to dispersal. In either case, the weathering affect was small compared to either flask speed or temperature. Dispersal did not show a consistent pattern with temperature increase. For most of the experiments, either the maximum or the minimum amount of dispersal occurred at the middle temperature of 22 °C

Abstract
Because of widely varying results from the EPA’s Swirling Flask test, the authors sought out sources of ambiguities in the method that may lead to different results in various laboratory tests. From this analysis, researchers recommended the use of a baffled flask for testing dispersants and developed the methodology for using the Baffled Flask test instead of the Swirling Flask method in the future

Abstract
Researchers conducted a series of experiments to estimate the repeatability of the three operators in both the Swirling Flask and Baffled Flask Test when determining the effectiveness of various dispersants. Statistical analysis revealed that the coefficient of variation for the Baffled Flask test was 7.8% versus 21.9% for the Swirling flask test. the Baffled Flask test measured 64.6% for mean percent effectiveness, compared with 19.7% for the Swirling Flask test

Abstract
This research focused on test spill data of relevance to DOOSIM, an oil spill simulation model. In all, four slicks were created, two as control and two with dispersants premixed with oil. The data collected was used to better understand vertical and horizontal spread of dispersed oil at sea

Abstract
Following the Torrey Canyon disaster, attention was directed to finding effective but innocuous means to combat the pollution risk of shipping oil. To introduce the minimum of chemicals into the sea, it was decided to use a little of a strong, but possibly more harmful, substance rather than more of a weaker and less offensive one. Marine life could be affected mechanically, chemically or by removal or dissolved O2. Various products were tested under laboratory conditions for effectiveness, and possible effects on marine life. It is noted that the latter is only a short-term view, and that different results might be obtained using different species as indicators. The range of effectiveness of products was considered. It was concluded that low density products should be sought as emulsifiers; solvents of low boiling point were best for viscous petrols; relative solubility in sea water was not a determining factor of efficiency; anionic detergents, polyglycol ethers and perchlorethylene should be avoided because of their toxicity

Abstract
Spilled oil was treated with 10,000 tons of dispersants during cleaning operations after the Torrey Canyon incident. Areas where dispersants were applied in great amounts showed almost no animals or algae after application, whereas areas where dispersants were applied in lesser amounts showed some animal and algae remaining. The general succession of recolonization was seen in a rapid “greening“ by Enteromorpha; followed by intense settlement and expansion of Fucus sp., resulting in a of surviving barnacles. Settlement of limpets and other grazing animals came next, and, eventually, the brown alga was replaced. Finally, the limpet population was reduced, followed by a resettlement of barnacles. Lightly oiled, wave-beaten rocks that received light dispersant treatment showed the most complete recovery, taking approximately 5 to 8 years. Heavily oiled areas receiving repeated dispersant application took 9 to 10 years and may not have completely recovered as yet

Abstract
This paper describes the results of a pipeline rupture and application of Corexit 7664 on the oil spill, and the effects of both oil and dispersant on the marine life in this area of the Arabian Gulf

Abstract
The effects on marine life of the excess of toxic detergents used to clean up the Torrey Canyon oil spill are summarized, with especial reference to algae and limpets. Similar effects after a bunker oil spill at Bouisand are noted, In the latter area, oil is still present (2 1/2yr later) in untreated gullies left as controls. The role of browsing fauna in oil removal is discussed

Abstract
Oil at sea affects chiefly species associated with the surface; damage at sea by oil and dispersants after Torrey Canyon were not as bad as expected. Slicks sometimes disappear naturally, how apart from physical actions may this be taking place? Bacteria can, under experimental conditions very favorable to their growth, assist in dispersal, sinking and decomposition of oil, and zooplankton can ingest oil droplets, but are these factors of significance at sea? On shores after Torrey Canyon, far more damage was done by excess detergent than by oil. Repopulation is following the expected sequence, most affected shores being still abnormal. Observations on oil left untreated in Cornwall, at Eleuthera and on the Devon cost show slow removal by various natural means, including the browsing action of fauna. Toxic detergents can affect the sublittoral zone, including species of economic importance. Areas liable to repeated pollution, such as estuaries and salt marshes, require special care. The use of new dispersants of low toxicity is desirable here and on shores

Abstract
The sensitivity of planktonic organisms to oil, whether naturally or artificially dispersed, is of obvious interest. The method described here enables an even dispersion of oil droplets to be continuously available by using vessels undergoing slow inversion on a wheel. Faecal pellet counts were used as a measure of activity, and the effects seen at the concentrations and times of exposure chosen were usually sublethal, survivors showing good recovery of feeding rate. The toxic effects of the oil may be operative in two ways, as solutes or actually ingested as droplets. Either of these may have a narcotic effect and possibly other consequences. A fuller account of this work is being prepared for publication

Abstract
Sub-lethal toxicity and recovery tests were made on feeding rates of 4 species of copepods using Kuwait oils kept in suspension on a slowly rotating wheel. Counts of faecal pellets from individuals fed on standard algal suspension were made after 20 h at 12°C. This exposure produced only marginal effects at 1 and 2 ppm, but 10 ppm produced definite effects on planktonic species. Recoveries were generally quite good from 'weathered' oiled treatments. Oils emulsified alone did not produce significantly different effects in these experiments from oils emulsified with dispersants

Abstract
A Canadian multi-authored appraisal of research on oil and dispersants has been completed recently. It resulted in a number of recommendations concerning research on oil spills, on relevant physical-chemical factors, effects of chemically dispersed oil on marine organisms, and strategies to minimize effects of oil spills in northern marine waters

Abstract
Ten oil dispersing agents were screened for acute toxicity. The agents were selected by 'Project Oil', the group concerned with cleaning up Bunker C oil in Chedabucto Bay following the wreck of the 'Arrow'. Most tests were performed in fresh water at 15 °C with Atlantic salmon (Salmo salar). A uniform stock of this fish was available and salmon proved more sensitive than the most suitable marine fish, winter flounders. American lobsters were extremely resistant and were used in only a few tests. Stirred static tests were used. The dispersant or oil-and-dispersant was initially emulsified in water using a blender. Acute toxicity to salmon of the dispersants without oil, could be described as follows: practically non-toxic (4 day LC50 is greater than 10,000 mg/litre), Corexit 8666; Slightly toxic (1,000-10,000 mg/litre), None; Moderately toxic (100-1,000 mg/litre), a sample of 'new' BP 1100B; Toxic (1-100 mg/litre), BP 1100B, BP 1100, G Gulf Agent 1009, Naphtha gas, Dispersant 88, Dispersol SD, BP 1002, and XZIT x-1-11. Bunker C oil by itself could be considered 'practically non-toxic' on the basis of 4-day tests, or 'slightly toxic' in 7-day tests. In equal-weight mixtures of oil and dispersant, Corexit 8666 could be termed 'moderately toxic'. BP 1100 and Dispersol SD were 'toxic', being lethal at somewhat less than 10 mg /litre of each component. Some results with low concentrations (approx 100 mg /litre) of Corexit 8666, suggested that a relatively strong delayed toxicity was caused either by toxic degradation products of Corexit, or by the bacteria bringing about degradation. These tests cover only acute effects. Sublethal or long-term effects might be important under some field conditions and should always be considered

Abstract
This paper reviews United Kingdom counter-pollution thinking over the past two years and with reference to the recently published Royal Commission Report on Environmental Pollution in respect of long and short-term environmental effects of oil pollution. It includes an update on present national plans, as well as the recent enhancement of the United Kingdom Marine Pollution Control Unit, and balance of resources between the use of dispersants and mechanical recovery. It assesses the complimentary nature of tugboats and aircraft dispersant sprayers in the U.K. mix of government-maintained resources and describes the deployment of mechanical recovery devices. U.K. air spraying capabilities include a number of different types of aircraft, considerations of their alert availability and choices of main and secondary airfields, the provision of dispersants and logistic backup organisations, and maintenance programs for the aircraft and flying fitness assurance programs for pilots. Possible future developments, including airborne remote sensing, also are described

Abstract
Chemical substances-dispersants-have been widely used to treat oil spills in the sea. The first opinion about the use of the chemical substance Simple Green® (SG) was expressed in Lithuania after the oil spills into the Baltic Sea near Būtingė on March, 6 and April, 23 2001. The aim of the present article is to investigate experimentally the impact of chemical dispersant SG on petroleum hydrocarbons (HC) distribution in the water of varying salinity and on settling petroleum hydrocarbons in bottom sediments. The impact of chemical dispersant on the oil distribution in the water was determined by evaluation of dffectiveness of dispersant. The SG effectiveness (EFF) in the water of different salinity (0, 5, and 7ppt) was 15, 21, and 33% respectively. The highest performance of SG in the experimental oil dispersion was recorded in the water with the salinity value of 7ppt. Samples of fine-grained sand (fractions 0.25-0.1 mm>50%; 0.24% Corg) and silty sand (fractions

Abstract
A variety of organic contaminants can potentially have impact on aquatic birds by their affecting surface tension. Avian plumage constitutes a porous barrier to water and the air trapped between the feathers serves as thermal insulation. When the air is displaced, the birds expend extra energy to maintain a normal body temperature, but this response cannot be sustained for long, especially at low environmental temperatures. When energy stores are depleted, hypothermia and death ensue. Surface tension is the force that resists infiltration of water into the plumage. The critical surface tension for feather wetting is conservatively estimated to be in the range 38–50 mN m-1. The hypothesis that surface-active organic contaminants can have significant detrimental effects on aquatic birds was evaluated. New data obtained in a study of water penetration pressures in Lesser Scaup contour feathers show that the 'wettability safety factor' is reduced by about half during moult. That is, the critical surface tension was raised to approximately 49–58 mN m-1 in moulting Lesser Scaup. The energetic and behavioural effects of oil contamination are reviewed, and it is concluded that even small quantities of organic material may confer significant physiological cost. The available data generally support the hypothesis that waterfowl face a potential risk associated with chronic or periodic mild depression of water surface tension due to organic pollutants, including oils and detergents. However, much of the evidence is indirect and further research, especially long-term assessment of surface tension in marine, estuarine and freshwater habitats, is needed to determine whether a real environmental problem exists

Abstract
Thermodynamic and kinetic investigations were performed to determine the influence of coalescence of chemically dispersed crude oil droplets in saline waters. For the range of pH (4–10) and salinity (10‰, 30‰, 50‰) values studied, ζ-potential values ranged from −3 to −10 mV. As the interaction potential values calculated using Derjaguin–Landau–Verway–Overbeek (DLVO) theory were negative, the electrostatic barrier did not produce significant resistance to droplet coalescence. Coalescence kinetics of premixed crude oil and chemical dispersant were determined within a range of mean shear rates (Gm=5, 10, 15, 20 s-1) and salinity (10‰, 30‰) values. Coalescence reaction rates were modeled using Smoluchowski reaction kinetics. Measured collision efficiency values (α=0.25) suggest insignificant resistance to coalescence in shear systems. Experimentally determined dispersant efficiencies (α=0.25) were 10–50% lower than that predicted using a non-interacting droplet model (α=0.0). Unlike other protocols in which the crude oil and dispersant are not premixed, salinity effects were not significant in this protocol. This approach allowed the effects of dispersant–oil contact efficiency (ηcontact) to be separated from those of water column transport efficiency (ηtransport) and coalescence efficiency (ηcoalescence)

Abstract
An integrated approach to study chemical dispersant effectiveness and dispersed oil toxicity is presented. Conventional lab scale effectiveness tests generally provide a measure of overall dispersant effectiveness. However, chemical dispersion can be viewed as two processes: (1) dispersant-oil slick mixing and (2) oil droplet transport into the water column. Inefficiencies in either process limit the overall dispersant effectiveness. This laboratory study centered on the latter process and was conducted to focus on the impacts of water column hydrodynamics on the resurfacing of dispersed oil droplets. Using a droplet coalescence model (Sterling et al., 2002), the droplet coalescence rates of dispersed crude oil was determined within a range of shear rates. A controlled shear batch reactor was created in which coalescence of dispersed oil droplets were monitored in-situ. Experimental dispersion efficiencies (C/C0) and droplet size distributions were compared to those predicted by Stokes resurfacing. Experimental C/C0 values were lower than that predicted from Stokes resurfacing. Experimental dispersion efficiency values (C/Co) decreased linearly with increasing mean shear rates due to increased coalescence rates. These results shear rates due to increased coalescence rates. These results suggested that dispersed oil droplet coalescence in the water column can adversely impact overall dispersant efficiency. To avoid high control mortality in toxicity testing, the toxicity exposure chamber was designed with separate compartments for scaled mixing and organism exposure, respectively. Chamber design includes continuous re-circulation between mixing and exposure chamber. A 1-minute exposure compartment residence time was determined from tracer studies indicating virtually identical oil concentrations in the mixing and exposure compartments. In addition, the 96-hour mortality of 14-day oil Menidia beryllina varied from 2% in the no-oil control tests to 87% in the dispersed oil (200 mg/L) tests. These results show the effectiveness of the integrated vessel for the characterization and toxicity testing of oil dispersions

Abstract
This paper describes guidelines for making decisions on dispersant use in New Zealand. The guidelines are designed to facilitate and document rapid and justifiable decisions for dispersant use during a marine oil spill, and were developed by modifying existing international models and information to suit N.Z. requirements. They are based around a simple flowchart that highlights the key question that need to be answered during a spill. Each key question in the flowchart is linked to supporting information that provides further details, or directs the decision maker--normally a statutorily appointed On-Scene Commander (OSC)--to where the information can be obtained. Although dispersant use is pre-approved in virtually all N.Z. waters, the guidelines do not provide hard and fast rules for when dispersants should or should not be used. The OSC is expected to judge, based on the information available and the type of values requiring protection, whether a dispersant response will result in a net environmental benefit, either on its own, or in combination with other response options. The guidelines provide a simple way to collect the information required to make decisions about dispersant use within a rapid, systematic, and flexible framework, with supporting information available where needed to make and document dispersant decisions. The guidelines are designed specifically for use during a spill response, and as such are self-contained, concise, and easy to read, and allow quick access to the information essential for deciding about dispersant use. While they rely on the decision maker being knowledgeable about dispersant issues, they generally will be of value to anyone involved in spill response planning and decision making

Abstract
Diesel oil and dispersants were used at rocky shore sites at Lamma Island, Hong Kong, to investigate effects on littoral fauna. A moderate level of diesel contamination, followed by application of dispersant, was found to cause the highest level of acute lethality in gastropods. Long-term disturbances were higher in heavily polluted sites with no dispersant added. Various species were collected at oiled sites and their recovery was monitored in a laboratory setting, using clean seawater, in the second part of this project

Abstract
The Poseidon Pipeline spill case study provides an excellent example of coordination within the Unified Command during response to an offshore oil spill where dispersants were used as the primary mitigation tool. Dispersants are an effective tool to mitigate oils spills if certain specific criteria are met, including an acceptable oil type, the application of dispersants is a preferred environmental trade-off to potential shoreline impacts, rapid approval is possible, and a dispersant delivery system is available. In the Gulf of Mexico, offshore pre-approval has been given to the Federal On-Scene Coordinator (FOSC) by the Regional Response Team (RRT). If the FOSC determines that the oil threatens sensitive coastal areas, he can grant approval quickly. As demonstrated in the Poseidon Pipeline spill case study, good field intelligence; accurate aerial observation information; close coordination between the responsible party (RP), state, FOSC, and their spill management teams; readily available dispersant application resources; and trained observers and monitoring teams are key elements to effective and environmentally beneficial dispersant applications