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Abstract
The toxicities of Prudhoe Bay crude oil, the dispersant Corexit 9527 and mixtures of these, to several arctic marine amphipods, one arctic marine copepod and one arctic marine fish were studied in semi-static 96 hr bioassays in which exposure concentrations were measured by fluorescence spectroscopy. In general, sensitivities of all species were remarkably similar for any one toxicant. The 96 hr LC50 values ranged from 28 to 66 mg/L for sodium lauryl sulfate (a reference toxicant), from 104 to 175 mg/L for Corexit, from 45 to 196 microfilters/L for Prudhoe Bay crude oil dispersed with Corexit 9527, and from 32 to 73 microliters/L for Prudhoe Bay crude oil dispersed mechanically. Mortality in oil-Corexit-water mixtures was much higher than in oil-water mixtures of the same nominal oil concentration. This was thought to be due to the higher concentrations of oil in the water column to which the organisms were exposed when the disperant was used. Based on measured hydrocarbon concentrations in the water column, the toxicity of the oil-Corexit-water mixtures was less than that found for the oil-water mixtures. This was attributed to the smaller ratio of dissolved hydrocarbons to total measured hydrocarbons in the oil-Corexit-water mixtures, than that in the oil-water mixtures

Abstract
Oil dispersants intended for use in United Kingdom waters have to be licensed under the Dumping at Sea Act, 1974. As part of the licensing procedure a dispersant must pass the MAFF 'sea' toxicity test, which assesses its effects on the toxicity of a standard oil (fresh Kuwait crude) to brown shrimps in stirred tanks in the laboratory. As an adjunct to this work the distribution of oil droplet sizes produced by 21 dispersants in this test have been determined using a Coulter Counter; this paper describes the results obtained and discusses the relationship between oil droplet size and toxicity under these standard conditions

Abstract
Although the National Contingency Plan states that the Federal On-Scene Coordinator (OSC) may authorize the use of dispersants on an oil spill, such authorization is not automatic. In practice, the applicant for permission to use dispersants must submit a plan which then will be considered by the OSC and others involved in the approval process. This plan generally must indicate not only that dispersant use is desirable as a means of mitigating the spill but also must show why use would result in lower environmental impact than if dispersants were not used. Some parts of a dispersant plan are time-consuming to prepare and require acquisition of large amounts of information. Fortunately, the most time-consuming parts can be prepared well in advance of any spill. If these parts are prepared in advance, decisions regarding dispersant use can be made in a timely fashion at the time of a spill. The components of a dispersant use plan should include the following: 1) Spill specific information such as how much of what oil was spilled, when did it occur, wind and sea conditions, and expected oil spill trajectories. 2) Information on resources available for dispersant application such as dispersant stockpiles that may be used, properties of these dispersants, application equipment, and information on application and monitoring methods. This information can be best gathered well in advance of any spill event. 3) Information on environmental impacts, including the comparative impacts of dispersed oil versus untreated oil. This information should be prepared and available in a form that will enable ready assessment at the time of a spill, of the trade-offs which must be considered. It should be possible to identify well in advance of a spill those areas in which dispersant use should be considered and those in which use might not be favored. 4) A guide or system for decision making; this guide will show how the above information is used in developing the on-scene decision for or against dispersant use. The decision making system should be agreed upon well in advance of any spill. 5) Recommendations regarding dispersant use on the specific spill incident and justification for the recommendations. Use of this planning method will expedite decision making at the time of a spill, will lead to more rational and logical dispersant use decisions, and will enable the decision maker to document his decision

Abstract
A decision for or against dispersant use involves several components, including considerations of operational feasibility and regulatory policy as well as environmental concerns. Eleven examples of the major published procedures for making oil spill response decisions, including decisions for or against use of chemical dispersants, are summarized and compared in this paper. These procedures are often depicted by decision diagrams, which are also included in the paper

Abstract
Guidelines are suggested for advance planning for the use or non-use of dispersants to combat oil spills. These guidelines are intended to expedite the decision to use dispersants in the event of an oil spill, where that will minimize environmental damage. These guidelines can be applied readily to any geographical area to answer the following questions: Are there locations where dispersant application would normally be allowed? In these locations, what rate of dispersant application should be allowed? Are there locations where dispersant application should normally be avoided? The logic behind these guidelines is explained so that exceptions can be identified and so that changes in the guidelines can be made as advances are made in the state of the art. These guidelines provide for control over dispersant usage while allowing application (in most instances) at rates which can disperse floating oil effectively

Abstract
The American Petroleum Institute Spill Response and Effects Task Force has developed guidelines (a "model plan") for use of dispersants on spilled oil. This model plan is consistent with subpart H of the National Contingency Plan and provides the information needed to implement subpart H. The model plan addresses the questions of where, when, why, and how dispersants should be used and what materials should be used. The components of the model plan are the following: Detailed descriptions of most of the currently used methods for making dispersant use decisions; A dispersant use information form (Federal Region VI format); Discussion of the technical basis for dispersant use decision making; Tabulations of properties (specific gravity, viscosity, pour point, and sulfur content) of oils transported through or produced in the area of interest, including an indication of relative dispersibility of each of these products; Inventories of dispersants and application equipment; A quality assurance/quality control plan; Literature on dispersant application techniques. The purpose of developing this model plan is to provide a format that may be used to establish consistent regional and local dispersant use plans throughout the country

Abstract
This report describes the development of a three-dimensional oil fate model. This model was used to predict oil behavior and concentration in the water-column resulting from spills with and without the use of dispersants as a countermeasure. The model accounts for the fate of the oil and its constituent elements as the oil breaks up and spreads into ecosystems and is exposed to organisms at the water surface, shoreline, and sediment. The model focuses on the weathering process, incorporating evaporation and dissolution rates by chemical class

Abstract
Oil spill response may include use of chemical dispersants and in situ burning equipment, in addition to traditional mechanical response equipment. To evaluate the potential impacts of various response strategies, oil spill and atmospheric plume modeling were performed to evaluate areas of the atmosphere at sea level, water areas, shoreline lengths, sediment areas, and water volumes impacted above thresholds of concern to biological species and habitats, human health and socioeconomic resources. For the oil spill monitoring, a stochastic approach was used to allow the range and frequency of possibly environmental conditions to be examined for each spill site, spill volume and response option evaluated. Long term (decade or more) wind and current records were sampled at random and model runs were performed for each of the spill dates-times selected. This provides a statistical description of the environmental fate and impacts that would result if a spill occurred. Stochastic modeling was performed in five representative locations in the US: (1) offshore of Delaware Bay, (2) offshore of Galveston Bay, (3) offshore of San Francisco Bay, (4) Prince William Sound, and (5) offshore of the Florida Keys. These data were used to evaluate potential impacts of changes in response strategies, i.e., combining use of dispersants and in situ burning with traditional mechanical recovery. The results of the oil spill modeling for the Florida Straits location are summarized herein

Abstract
Static and flowthrough aquatic acute toxicity testing protocols were utilized on egg and larval stages of seven commercially important invertebrate and fish species from the Gulf of Mexico. Test organisms were exposed to two different oils (from the Western and Central Gulf of Mexico), dispersed oil, and a single dispersant (Corexit 9527). Species evaluated Included brown shrimp (Penaeus aztecus), white shrimp (P. setiferus), blue crab (Callinectes sapidus), eastern oyster (Crassostrea virginica), red drum (aka redfish or channel bass, Sclaenops ocellatus), inland silverside (aka silverside minnow, Menidia beryllina), and spot (Leiostomus xanthurus). In lieu of acute toxicity testing on gulf menhaden (Brevoortia patronus), which were unavailable, a congener (Atlantic menhaden, B. ryrannus) was evaluated using study-speck acute toxicity testing protocols for comparative purposes. Mysids (Mysidopsis bahia) were also evaluated as part of a chronic toxicity assessment. A total of 292 chemical analyses were conducted on oil (i.e., the water accommodated fraction, WAF) and dispersed oil at various phases of acute toxicity testing to characterize the degradation of oil and oil dispersant mixtures. Oil characterization tests were also conducted on both oils at the beginning and end of the study to determine if the oils changed significantly. Further, seven analyses were performed on a Corexit 9527 exposure to determine total petroleum hydrocarbon (fPH) and polynuclear aromatic hydrocarbon (PAH) background concentrations. The two oils showed minor chemical differences. Naphthalenes were present in the highest concentrations in both oils (i.e., 420 to 510 mg/g) and were generally several times greater than the other PAH compounds analyzed. For the acute toxicity testing, static tests tended to have the highest overall TPH concentrations with the dispersed oil levels being four to five times greater than that measured in the WAF. Flowthrough concentrations tended to be more variable without the clear distinctions seen in the static tests. Replication between the various flowthrough exposures was good, particularly with regard to hydrocarbons. Given that only a limited number of comparable study efforts have been completed on these early life stages, these results are increasingly important. The finding is particularly noteworthy in comparisons between various flowthrough tests, where total naphthalenes for both the Western and Central Gulf oils were approximately three times that of the WAF. Because a complete characterization of hydrocarbons in test media could not be accomplished for every toxicity test, this finding is quite important as it allows one to extrapolate between tests. Agreement in the static exposures was less evident, suggesting that greater variability is likely in toxicity results originating from this exposure method. The chemical characterizations may explain many of the anomalies observed in the toxicity data. Much of the variability that was seen in the fish tests may be attributed to the fact that most of these tests were run under static conditions, where some of the greatest variability in TPH concentrations was obtained. By comparison, the TPH, naphthalenes, and BTEX (benzene, toluene, ethylbenzene, xylene) concentrations were relatively uniform in flowthrough tests where most of the invertebrate exposures were completed. An important and historically-consistent finding in these tests was the lower sensitivity of the embryonic stages compared to the early larval stages. The overall sensitivity of the fish versus invertebrates appears to be similar. Invertebrates performed better as test organisms, as overall survival in controls was better. The naturally high mortality of the fish larvae compounded efforts to obtain acceptable test results and necessitated repeating several of the tests many times. The invertebrate tests, however, were generally accomplished with good control survival and results. BTEX compounds were a possible source of toxicity in the WAF exposures, whereas naphthalenes appeared to be the primary cause of toxicity in the dispersed oil exposures

Abstract
The early life stages of seven invertebrate and vertebrate species from the Gulf of Mexico were exposed to two oils, Corexit 9527, and dispersed oil mixtures. Chemical analyses found that hydrocarbon concentrations between exposures were relatively consistent. The hydrocarbon concentrations were initially highest in the dispersed oil mixtures compared to the water accommodated fractions (WAF) of the oils. However, hydrocarbon concentrations in both dispersed oil and WAF exposures were generally similar after 24 hours. The levels of toxicity in the dispersed oil mixtures were not proportionately greater than that in the WAF

Abstract
Dispersants are one class of chemical response agents currently approved for use on offshore oil spills. However, questions persist regarding potential environmental risks of nearshore dispersant applications. To address these questions, the relative toxicity of weathered crude oil, dispersant, and weathered crude oil plus dispersant were compared. This study included one luminescent marine bacteria (Vibrio fisheri), two marine vertebrate (Cyprinodon variegatus and Menidia beryllina), and one invertebrate test species (Mysidopsis bahia). Both the vertebrate and invertebrate species were tested under spiked (short episodic) exposure regimes and 96-hour continuous exposure regimes using protocols developed by the Chemical Response to Oil Spills: Ecological Effects Research Forum (CROSERF) and U.S. Environmental Protection Agency (EPA), respectively. Toxicity to the marine bacteria was evaluated after a 15-minute exposure using the Microbics Microtox® system. Results showed no significant variance between the relative toxicity of solutions prepared with weathered crude oil only and weathered crude oil plus dispersant when evaluated with the vertebrate and invertebrate test species. However, oil only solutions were shown to be significantly more toxic to Vibrio fisheri than oil plus dispersant solutions. Data also indicated that constant exposures were significantly more toxic than declining exposures, which is generally consistent with time weighted exposure response evaluations. Microtox® data was comparable to both vertebrate and invertebrate test results suggesting that the method is suitable for toxicity field screening

Abstract
This study evaluated the relative toxicity of Corexit 9500, weathered crude oil, and weathered crude oil plus dispersant. Fish (Cyprinodon variegates and Menidia beryllina) and shrimp (Americamysis bahia) were chosen for these experiments, while the bacteria Vibrio fisheri was used to determine microbial toxicity. Results indicate that oil/dispersant mixtures were either equally or less toxic than oil alone. Data suggested that continuous exposures to the material were generally more toxic than declining exposures. Unweathered crude was also tested for toxicity, using M. beryllina in declining exposure conditions. Total concentrations of hydrocarbons in oil/Corexit mixtures using weathered and unweathered crude oil were both dominated by colloidal oil and showed no significant difference in toxicity. Toxicity was believed to be a function of the soluble crude oil components

Abstract
The current SMART protocol used by the U.S. Coast Guard relies on traditional ex-situ fluorometers that require physical transport of the sample from the water column to the instruments. While sample transport methods are available (e.g. pumps and discreet sampling), they introduce time lags in the data acquisition process. These lags can be a source of error when the data is post analyzed and is not conducive to real-time monitoring efforts, creating significant logistical problems and dispersion (smearing) of the sample stream. Another limitation of the currently-used equipment is that it requires much attention to manually record GPS data which is later used to determine the spatial distribution of an oil plume. Recent developments of in-situ fluorometric instrumentation promise to simplify problems associated with the deployment of ex-situ instrumentation (e.g. insuring that pumps are primed) in boat-based field applications. This study first compares the performance of two in-situ fluorometers in a simulated oil and dispersant application at the Shoreline Environmental Research Facility at Texas A&M University in Corpus Christi, Texas. The fluorometers were the WETStar and the ECP-FL3 (both by WETLabs, Inc.). To address issues related to data collection from a GPS and a fluorometer, a system was developed that simultaneously merges data from both instruments into a single file and presents the data real-time as a color-coded ship track. The applicability of this system was tested and evaluated during a spill response exercise conducted by the Texas General Land Office and the U.S. Coast Guard in Galveston Bay, Texas, U.S.A

Abstract
Metabolic effects of low-level exposure of Atlantic salmon (Salmo salar) to the water accommodated fraction (WAF) of crude oil and to dispersed crude oil were studied. Aerobic enzymes citrate synthase and cytochrome C oxidase, and anaerobic enzyme lactate dehydrogenase were measured in gills during a 4-day exposure to low concentrations of dispersed Bass Strait crude oil and WAF, and during the following 8 days of depuration in clean seawater. Relative to pre-exposure levels, citrate synthase and lactate dehydrogenase exhibited a significant inhibition of activity during exposure to the WAF of crude oil, and to dispersed crude oil, while activity of cytochrome C oxidase remained unchanged. Citrate synthase activities returned to pre-exposure levels after 4 days following termination of exposure for the WAF-exposed fish, and after 2 days for the dispersed-oil-exposed fish. After the termination of exposure to both treatments, lactate dehydrogenase activity remained low relative to levels measured prior to exposure, which indicated that the activity of this enzyme may be a sensitive medium to long-term biomarker of exposure to petroleum-contaminated water bodies

Abstract
Immature Atlantic salmon (Salmo salar) were exposed to water accommodated fraction (WAF) of Bass Strait crude oil or to Corexit 9527- dispersed crude oil for 6 days, followed by a depuration period of 29 days. Serum sorbitol dehydrogenase (SDH) levels, indicator of liver damages, remained low during the experiment. Hepatic EROD activity was induced within 2 days following the onset of the exposure in both treatments, and persisted for 2-4 and 4-6 days after transfer to clean sea water in the WAF and dispersed oil treatment, respectively. Naphthalene-type metabolites, determined by fixed-wavelength fluorescence detection, appeared in the bile of the fish with 2 days' delay compared to EROD induction. In both treatments, EROD activity induction and levels of naphthalene-type metabolites in the bile were significantly related. The biliary levels of naphthalene-type metabolites were over 15 times higher in fish exposed to dispersed crude oil relative to fish exposed to the WAF of Bass Strait crude oil. BaP-type metabolites appeared only in the bile of the fish exposed to the WAF, possibly due to BaP-type compounds remaining associated with the dispersant in the water column or to an inhibition of Phase II detoxification enzymes by the dispersant. Bile metabolites as determined by fixed-wavelength fluorescence and EROD induction appear to be sensitive and complementary biomarkers of exposure to PAH

Abstract
On 14 March 2001, the M/V GENMAR HECTOR was oiled on both the superstructure and hull after a transfer line broke during an unexpected storm event with winds gusting to 70 mph. In addition to the tanker vessel, seven other vessels, as well as floating docks and barges, were oiled at the waterline. The crude oil rapidly weathered to the point that conventional cleanup techniques were ineffective at removing residual oil from the vessels so that they could be released from the port area. Members of the Regional Response Team were convened and the use of National Contingency Plan listed surface-washing agents that had the effect of “lifting and floating” remobilized oil was approved. Using the guidance of the Regional Response Team, a test was conducted to evaluate conventional and chemically-enhanced washing techniques. It was found that pretreatment with PES-51 followed by a high pressure, hot water wash resulted in the desired cleanup level, which was, essentially, the complete removal of oil and oil stain. PES-51 was selected for this application because of its availability and the minimal contact time required before flushing. The cleaning and demobilization of oiled vessels was greatly enhanced by using a surface-washing agent

Abstract
The paper is a comprehensive report on the efforts made to limit the pollution effects of the Santa Barbara oil spill of Jan 28, 1969. The use of polyelectrolytes and dispersants is reviewed. Application techniques and their effectiveness are discussed. The role of the Federal Water Quality Administration in the occurrence is included. Containment of the oil slide with a boom was unsuccessful. An attempt was made to use booms to protect the shore line, but heavy seas prevented their use. After the beaches were inundated with oil, cleanup efforts were started with a peak labor force of 1,000 men. Over 30,000 tons (27,000 metric tons) of storm debris were cleaned up. A system of containment for undersea seepage is described. A complete equipment list and progress report is included in the paper

Abstract
The method of studying algal metabolism by analyses of dissolved O2 and its diel changes, correlated to concentrations of oils and dispersed oil is used in this investigation. Fucus vesiculosus L. was placed in tubs of sea water mounted on a raft with the water bodies almost submerged, so that the temperature of the tubs followed the ambient water temperature. O2 analyses were carried out every 3rd hr with a battery-operated polarographic O2 meter. Oil and oil emulsions were added and O2 recordings made. The algae were dried at 105 °C for 7 days and all calculations reproduced per g algae dry weight. Results show an increase in community respiration with increasing concentration of both oil and oil emulsion. Gross primary production, however, decreases immediately with fairly low concentrations of emulsified oil (100 or 560 ppm), but it requires a concentration of 1000 ppm of oil alone to produce this effect. It was found, too, that recovery after 14 days of exposure to oil concentrations of 1000 ppm was possible but emulsified oil was much more harmful. In the Baltic where the water is cold and there is no tidal movement, high conncentrations of oil are likely to be reached, and such areas should therefore be cleaned by mechanical means and not with emulsifiers

Abstract
Two algal species, one sensitive to dispersant EPN-5 (mono and hybrid cultivated Anacystis nidulans and a resistant species (mono and hybrid cultivated Synechocystis aquatilis) were exposed to the dispersant at concentrations of 0.1 and 0.2 g/l for 24 days. Concentrations at 0.2 g/l were lethal for both species. Concentrations at 0.1 g/l did not inhibit growth of the hybrid A. nidulans in the manner the mono-cultured species was impacted. The hybrid cultured form of S. aquatilis experienced immediate lethality, without a secondary resurgent growth that was evidenced in the mono-cultured segment of the species. Results support the observation of mutual influence of algae during hybrid cultivation

Abstract
Adaptation of S. aquatilis and A. nidulans to this dispersant depended on both the time of the contact of algae with it and its concentration. S. aquatilis adapted even to the lethal concentration DN-75 after preliminary growth in the medium with toxic concentrations of dispersant. A. nidulans adapted to toxic concentration DN-75 after preliminary growth in the medium with atoxic concentrations of dispersant. Data suggest that there is probably physiological adaptation of blue-green algae S. aquatilis and A. nidulans to dispersant besides the selection of the resistant forms in the initial population of algal cells already capable of growing in the presence of toxic concentrations of D-75

Abstract
S. aquatilis and A. variabilis were used to test the effects of oil, oil products, and dispersants. Of 12 pairs of oil/dispersant and oil product/dispersant mixtures, six showed a decrease in toxic effect of the petroleum product when compared to product alone

Abstract
This paper examines selected aspects of dispersant usage from a practical point of view and with reference to the experience gained from oil spill incidents around the world. The factors to be considered when deciding what, if any, response should be employed in the event of an oil spillage are discussed and the importance of well-prepared contingency plans are stressed. Environmental considerations are of obvious importance in deciding whether or not dispersants should be used but it is explained that ultimately the decision will not depend upon the priorities for protection and the unique circumstances of each incident. It is emphasized that the effective use of dispersants from vessels and aircraft depends upon good initial evaluation of the response required and continual control of the whole operation. Aerial surveillance is essential to continually reevaluate and direct the response in an ever-changing situation. It is concluded that dispersants, applied correctly and after a detailed consideration of the particular circumstances of the incident, have a role to play in combating oil spillage at sea and can prevent or reduce damage to coastal resources and amenities. They should be regarded, however, only as one of the many courses of action open to cleanup controllers and not as a panacea for all ills

Abstract
The degradation of hydrocarbons by marine microorganisms is discussed in relation to the use of suitable non-toxic dispersants to accelerate this decomposition. The role of temp, aeration and nutritive elements in facilitating decomposition is also considered. An experiment is described which assesses the effect of several dispersants on ecosystems containing pollutant by analysing the hydrocarbons remaining at the end of the experiment, also measuring the photosynthesis, which occurred, and evaluating the residual toxicity. Results obtained show that most commercial surface active agents increase the initial inhibition of photosynthesis observed with crude oil and also stop the natural microbial colonization of the petroleum fractions. Experimental products, which were mixtures of true dispersants and fertilizers were found to be greatly favourable to plankton (O2 source) and degrading bacteria