Dispersants Bibliography

Abstract
The monitoring of oil concentrations in the water column during a dispersant operation carried out at the Sea Empress incident has clearly demonstrated that, although a monitoring program should not be viewed as a prerequisite to response (since the spill site may be too remote to allow monitoring to be set up for the start of the response operation), if monitoring is planned as part of the response, it enables operations to be executed efficiently. The estimates put forward in this paper indicate that the targeted use of dispersants probably prevented 57,000 to 110,000 tons of emulsion from impacting the shoreline and potentially resulting in greatly increased impacts on sea birds, coastal waders, intertidal vertebrates and invertebrates, and amenity areas. The paper shows that these benefits outweighed the potential disadvantages associated with elevated oil concentrations in the water column. The Sea Empress is the first incident that has been monitored in a timely fashion in sufficient detail. The monitoring program demonstrated that the use of dispersants resulted in a net environmental benefit at the Sea Empress incident

Abstract
The North Sea field tests described in this paper have provided a quantitative data set on dispersant efficiency that can be used to calibrate laboratory dispersant test. Comparisons of efficiency figures from the EXDET, IFP, Swirling Flask, and WSL test with the field dispersant efficiency figures indicate that the WSL test comes closest to replicating the observed dispersion, in terms of both the percentage of oil dispersed and the oil droplet size of the dispersion. This paper, with the accompanying presentation in the Sea Empress session of the conference, demonstrates that a combination of quantitative field tests and the WSL test can be used to guide responders in decisions of whether to use dispersants in response to an oil spill. The WSL test and the field trials indicated that dispersants were likely to be effective against both the Forties Blend crude oil and the weathered oil. These predications were confirmed by the successful dispersant operation of the Sea Empress incident

Abstract
The use of oil spill dispersants can, in some circumstances, be an effective response measure that reduces the overall environmental or economic damage caused by oil spills. In recent years, there have been some developments in dispersant formulation and in situ monitoring techniques which have led to an increase in the potential "time window" for dispersant use and also an increase in the number of oil types where dispersant treatment is considered a possibility. Perhaps more importantly, a more realistic understanding of the capabilities and limitations of oil spill dispersants combined with in situ monitoring methods for assessing the different potential impact of oil spills, has led to more informed decision-making about dispersant use. This paper considers recent technological developments that have been made relating to dispersant use, addresses the issues and identifies areas where further effort is needed

Abstract
This note describes elements of the counter-pollution response to the 72,000 t (19 million gallons) of Forties Blend and 370 t of Heavy Fuel Oil (HFO) spilt during the Sea Empress incident in Milford Haven (U.K.). It is estimated that the successful dispersant operation at the Sea Empress incident prevented 57,000-110,000 t of emulsion impacting the South Wales coastline. Had the volume of oil beaching been around 130,000 t, rather than the 10,000-15,000 t that actually came ashore, then the impact on sea birds, coastal waders, intertidal invertebrates and amenity areas would have been much greater. No significant effects to the marine environment have been attributed to the dispersed oil concentrations, which were observed to dilute rapidly to below 1 ppm. Therefore, the Sea Empress incident has demonstrated how a targeted dispersant response can provide a net environmental benefit in responding to an oil spill

Abstract
Small concentrations of Tween 80 were found to cause a decrease in mating success of G. duebeni. Tween 80 interfered with receptors on the antennae of the male, blocking a chemical cue that normally results in synchronized mating with the suitable phase of ecdysis in the female

Abstract
Initial experiences with oil spill dispersants were less than positive somewhat due to the fact that dispersants began their evolution as chemical substances that were perhaps more toxic than the oil that they were intended to disperse. Through time, however, dispersants were formulated to become less toxic. Beginning with caution, testing and evaluation through the U.S. national science community, then through public workshops and hearings, the U.S. began the process of integrating dispersant usage into its repertory of response technologies

Abstract
The present report provides a basis for direct comparison of the susceptibility of fish to alkylphenol and alcohol ethoxylates of various EO chain lengths. It is obvious from the data provided that susceptibility of bluegill to nonionic surfactants (both types) increases with decreasing EO chain length. Also it appears that bluegill are no more susceptible, and, in fact, are probably less susceptible to the acute effects of alkylphenol ethoxylates than of alcohol ethoxylates

Abstract
We used photosynthetic activity (measured as chlorophyll a fluorescence) and photosynthetic pigment concentrations to assess the effect of pulsed exposures of aged crude oil (Champion Crude), dispersant (VDC) and an oil + dispersant mixture on the seagrass Zostera capricorni Aschers in laboratory and field experiments, using custom-made chambers. Samples were exposed for 10 h to 0.25% and 0.1% concentrations of aged crude oil and dispersant as well as mixtures of 0.25% oil + 0.05% dispersant and 0.1% oil + 0.02% dispersant. During this time and for the subsequent four day recovery period, the maximum and effective quantum yields of photosystem II (Fv/Fm and ΔF/Fm’ respectively) were measured. In the laboratory experiments, both values declined in response to oil exposure and remained low during the recovery period. Dispersant exposure caused a decline in both values during the recovery period, while the mixture of aged crude oil + dispersant had little impact on both quantum yields. In situ samples were less sensitive than laboratory samples, showing no photosynthetic impact due to dispersant and oil + dispersant mixture. Despite an initial decline in ΔF/Fm’, in situ oil-exposed samples recovered by the end of the experiment. Chlorophyll pigment analysis showed only limited ongoing impact in both laboratory and field situations. This study suggests that laboratory experiments may overestimate the ongoing impact of petrochemicals on seagrass whilst the dispersant VDC can reduce the impact of oil on seagrass photosynthesis

Abstract
A research project is described in which a previously described effectiveness test for chemical oil spill dispersants was further developed and standardized. The principle of the test is that known volumes of dispersant and crude oil are contacted on the surface of seawater in a laboratory-scale vessel in which there is a circulating air current that imparts a swirling wave action to the water. This flow geometry is believed to simulate ocean surface conditions better than tests that involve shaking, stirring, or pumping as turbulence-generating mechanisms. From the results of a series of tests at various dispersant-to-oil ratios, the ratios that affect the dispersion of 50 and 75 percent of the original amount of oil added to the water surface are calculated and used as an indication of dispersant effectiveness. The corresponding percent of the oil that remains dispersed after settling is also deduced. The results of a series of tests using two crude oils, Murban (light) and La Rosa (heavy), and 17 dispersants are presented. These results show a wide range in the dispersant-to-oil ratio necessary to achieve 50- to 75-percent dispersion. Five products failed to achieve 50-percent dispersion of both crude oils at a dispersant-to-oil ratio of 0.2, which is highly regarded as the practical upper limit of dispersant dosage. There was a group of highly effective dispersants requiring a dispersant-to-oil ratio of only 0.005 to 0.007 to accomplish 50-percent dispersion. The test method can discriminate between two dispersant products with effectiveness which differ by approximately 10 percent. The implications of these experimental results are discussed

Abstract
Equations were created to describe the unsteady state diffusion of chemically dispersed oil in the water column. The equations create profiles accounting for concentrations of dispersed oil (volume) by time and depth, with a minimum number of adjustable parameters. The equations could be used to estimate lethal and sublethal effects to organisms in the upper water column

Abstract
Three key issues must be addressed when deciding on the desirability of using chemical dispersants for mitigating the adverse effects of oil spills: (1) how effective a given dosage of dispersant will be on a given oil slick; (2) how the dispersed oil and dispersant diffuse into the water column, dissolve, volatilize, degrade, and interact with suspended and bottom sediments; and (3) what effects the dissolved and particulate oil and dispersant will have on water column and benthic biota. It is essential that the first two areas (physical and chemical studies) relate closely to the third (biological aspects) in order that bioassay exposure (in terms of concentration of dispersant, classes of and individual hydrocarbons, and duration) addressing the toxicity issue be realistic. Here, we review the current status of a research program which addresses these issues. Under the program, attempts are being made to quantify dispersant effectiveness (including consideration of effectiveness testing using the Mackay-Nadeau-Steelman system for oils which have evaporated and/or formed water-in-oil emulsions to various extents), water column diffusion, and partitioning of specific hydrocarbons among water, oil, and suspended sediment as well as into the atmosphere. A procedure is described which has been used to quantify the acute toxicity of dispersants to copepods and which is being extended to apply also to the toxic contributions of dissolved and particulate oil. Hopefully, by assembling quantitative expressions for effectiveness, behavior, and toxicity, those situations in which dispersion is desirable can be better identified

Abstract
Recent developments in effectiveness testing of dispersants are discussed, with emphasis on the Mackay-Nadeau-Steelman laboratory test. A novel flume test system is described in which an attempt is made in the laboratory to simulate a sea test involving continuous application by boat. Some recent findings of test programs are discussed and a detailed mechanism proposed for the dispersion process. It is proposed that a mathematical model be sought to express effectiveness as a function of the volumes of oil, water, and dispersant, oil viscosity, water salinity, and application method. It is suggested that this model could form the basis of a procedure for correlating effectiveness and linking laboratory tests to application conditions at sea

Abstract
The effectiveness of dispersants in the laboratory and at sea is described. Some of the factors influencing effectiveness are: chemical composition of dispersants and oil, ratios of oil to dispersant, and physical properties affecting the ability of dispersants to mix at the surface and in the water column when applied to a spill. The need to quantify dispersant effectiveness at sea is stressed; areas that should be investigated further include how much to apply given the thickness of a slick, understanding the effect of weathering, and the physical processes of the sea at the surface

Abstract
Results are presented from two projects focusing on the behavior of oil spills on ocean surfaces. One study investigated aspects of the process of chemical dispersion of oil spills by observing and quantifying processes that occur when droplets of dispersant land on a slick and induce dispersion. Another investigation looked at factors that lead to an oil slick breaking up into discrete droplets on the ocean surface, how droplets may combine to form larger oil pans or pancakes, and how these droplets and pans of various sizes tend to become submerged and undetected

Abstract
A small scale laboratory system is described in which known amounts of oil and dispersant are introduced on a water surface at a controlled temperature and turbulence and the dispersion behavior observed. Turbulence is provided by circulating an air current over the oil-water surface, thus simulating, to some extent, natural wave action and avoiding the atypical turbulence introduced by mechanical agitation devices. Oil adherence to solid surfaces is minimized. The apparatus is believed to particularly suitable for observing the effectiveness and behavior of dispersants under conditions where little or no artificial turbulence is provided. The design and performance of the apparatus is described and some results presented in which turbulence, oil-to-dispersant ratio, and temperature are varied. The system is suitable for close observation of the dispersion process and subsequent emulsified oil behavior. The advantages and disadvantages of the system are outlined and the possibility of relating sea state to conditions in the apparatus are discussed

Abstract
A laboratory experimental program was conducted in which the aims were to investigate quantitatively the factors which influence the effectiveness of chemical dispersants (1) when applied to oil under various open sea conditions, and (2) in modifying the behavior of oil advancing on a shoreline. Open sea conditions were simulated in a previously-devised dispersant effectiveness test apparatus. The effectiveness of a dispersant was shown to be profoundly influenced by turbulence level. An approach also was made to relating the turbulence level in the apparatus to natural environmental conditions. A simulated shoreline, impacted by waves from a wave generator, was used to examined the behavior of crude oil and No. 6 fuel oil on the shorelines with and without dispersant additions. Wave action caused sand beaches to “filter” dispersed oil from the water column, resulting in enhanced, but possible reversible, oil penetration. Larger oil particles were observed to capture sand particles and sink. Implications of the results are that in many situations the use of dispersants on oil advancing on shores or even on the shoreline itself could prove advantageous

Abstract
A study is described in which the effectiveness of Corexit 9527 on Alaskan North Slope crude oil was assessed by conducting laboratory and wave basin tests. Three laboratory dispersant test systems were used: the MNS, Labofina and EXDET procedures. It was concluded that for the present purposes the EXDET system was most suitable, and it was used for subsequent tests. The dependence of effectiveness on dispersant to oil ratio, extent of weathering, temperature, water salinity, energy level and the presence of emulsified water (mousse) were determined. The results were used to guide a subsequent program of tests at the Esso Resources Canada Ltd. Wave Basin in Calgary in which the effectiveness was determined under breaking wave conditions. From the results a correlating equation was developed to express effectiveness as a function of dispersant to oil ratio and delay time between dispersant application and the onset of breaking waves. Significant quantities of oil were dispersed under breaking wave conditions, even at what are conventionally regarded as low dispersant to oil ratios. The implications of the results for assessing the actual and potential extent of chemical dispersion following the Exxon Valdez spill in March 1989 are discussed. Assuming that the dispersion efficiencies from the wave basin could have been achieved at the incident, it is believed that because of the onset of the storm with breaking wave conditions some 60 hours after the grounding, approximately 38% of the spilled oil could have been dispersed had available dispersants been applied to the spilled oil in the days following the grounding

Abstract
The substance present in extracts of Marthasterias glacialis (L.) which induces avoidance reactions in Buccinum undatum (L.), Chlamys opercularis (L.), Pecten maximus (L.), Ophiothrix fragilis (Abildgaard) and Patella vulgata L. has been shown to be a steroid glycoside with surface-active properties. Such reactions may also be obtained with equally low amounts of synthetic non-ionic surface-active agents. Maintenance of Buccinum undatum in a sub-lethal concentration of one of these non-ionic surfactants caused damage or fatigue to chemoreceptor cells on the surface of the foot. The possible significance of these results to pollution studies is discussed

Abstract
For oil spills in the open sea, operational experience has found that conventional response techniques, such as mechanical recovery, tend to remove only a small fraction of oil during major spills, a recent exception being the Mississippi River spill in Louisiana [Spill Sci. Technol. Bull. 7 (2002) 155]. By contrast, the use of dispersants can enable significant fractions of oil to be removed from the sea surface by dispersing the oil into the water column. It is thought that once dispersed the oil can biodegrade in the water column, although there is little information on the mechanism and rate of biodegradation. Two studies were undertaken on dispersion, microbial colonisation and biodegradation of Forties crude and Alaskan North Slope (ANS) oils under simulated marine conditions. The study using the Forties crude lasted 27 days and was carried out in conditions simulating estuarine and coastal conditions in waters around the UK (15 °C and in the presence of nutrients, 1 mg N-NO3/l), while the ANS study simulated low temperature conditions typical of Prince William Sound (8 °C) and took place over 35 days. The results of both studies demonstrated microbial colonisation of oil droplets after 4 days, and the formation of neutrally buoyant clusters consisting of oil, bacteria, protozoa and nematodes. By day 16, the size of the clusters increased and they sank to the bottom of the microcosms, presumably because of a decrease in buoyancy due to oil biodegradation, however biodegradation of n-alkanes was confirmed only in the Forties study. No colonisation or biodegradation of oil was noted in the controls in which biological action was inhibited. Oil degrading bacteria proliferated in all biologically active microcosms. Without dispersant, the onset of colonisation was delayed, although microbial growth rates and population size in ANS were greater than observed with the Forties. This difference reflected the greater droplet number seen with ANS at 8 °C than with Forties crude at 15 °C. Although these studies differed by more than one variable, complicating comparison, the findings suggest that dispersion (natural or chemical) changes the impact of the oil on the marine environment, potentially having important implications for management of oil spills in relation to the policy of dispersant use in an oil spill event

Abstract
Using dispersants to mitigate oil spills has remained controversial, despite considerable testing, in both the laboratory and the field. One of the major concerns, which has not been satisfactorily resolved, is how effective various dispersants are on different oils over a range of environmental conditions. Laboratory experiments cannot accurately simulate the real world, while field experiments are difficult to monitor and control. To eliminate some of the problems previously encountered when testing dispersants, an experiment was conducted in a large (approximately 30 m x 55 m x 2.5 m deep) outdoor wave test basin. The main objective of the experiment was to test the action of Corexit 9527 on unweathered Issungnak crude oil in low energy, nonbreaking waves. Eight tests were conducted, four on control oil slicks and four on treated slicks. The oil was contained in a 4.6 m diameter boom with a l.85 m deep skirt. The boom was moored at one end of the test basin 6 m from a wave generator, which could generate waves up to 0.4 m high. At the opposite (shallow) end of the wave basin, a gravel beach absorbed the energy of the waves. For each test, the wave generator was run for about 4 hours, with a constant wave height (set from 10 to 28 cm) and period (l.6 s). During this time, water samples were drawn at regular intervals from various depths for measuring oil concentrations in the water column. The data indicated that, in 10 and 20 cm nonbreaking waves, dispersion of oil into the water column from an untreated oil slick was negligible. During all the experiments for treated slicks, concentrations of oil in the boom were dramatically higher than for untreated slicks. Even in quiescent conditions, concentrations as high as 4ppm were observed at 50 cm after 24 hours under a treated slick. Concentrations of up to 60 ppm were observed at 50 cm in the water column in 10 cm waves. Investigations of oil drop size showed that under the treated slicks the oil droplet diameters ranged from 1 µm to 8 µm diameter. Overall, the results showed that, even in low energy waves, there was a significant increase in dispersion from a surface slick of unweathered Issungnak oil when it was treated with Corexit 9527, and the oil in water emulsion formed was more stable than that from an untreated slick