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Abstract Oil spill response strategies are designed to minimize environmental impacts tothe extent possible. Each response option must be evaluated for operationallimitations (e.g., sea state), potential effectiveness, environmental impactsof the response option itself, and applicability under various oil spillscenarios (e.g., size and location of the spill) in addition to health andsafety of the responders. Although mechanical recovery is often favored for its ability to directlyremove oil from the environment, it has long been recognized that for largeoffshore spills this technology has significant limitations. In addition toknown operational limits in the presence of currents and waves, thedynamic-nature of offshore oil slicks, i.e., rapid spreading and movement, hasresulted in mechanical recovery only treating a small fraction of spilled oilin the past. Because of these limitations, the oil and gas industry has workedto develop alternative response tools that can be used in addition tomechanical recovery to more effectively treat large offshore oil spills. This paper provides a review of the primary oil spill response options, adetailed discussion that addresses misperceptions and misunderstandings aboutdispersants and their use, and a description of dispersant use during theDeepwater Horizon incident including the important health and safety aspects ofsubsea dispersant injection. The information provided will support the use ofdispersants as a primary response tool for large offshore oil spills when thegoal is to minimize environmental harm. Introduction The primary goal of any oil spill response operation should be to minimizeenvironmental harm. Although one expectation may be the complete physicalcontainment and removal of oil from the environment, this is often not possible(especially with large offshore spills) due to physical limitations ofmechanical recovery systems. In fact, recovery operations during previousoffshore spills only collected a small fraction of the spilled oil even underideal conditions (ITOPF Handbook, 2010). The Deepwater Horizon incident was noexception, with estimates indicating that only 3% of the oil was mechanicallyrecovered (NOAA Oil Budget, 2010). Relying solely on mechanical responsemeasures for large offshore spills may, therefore, result in less effectiveprotection of the environment. Recognition of the significant limitations of mechanical recovery has led todevelopment of alternative response tools—one of which is oil spilldispersants. Oil spill dispersants facilitate removal of oil from theenvironment by enhancing the natural biodegradation process. Dispersantsrapidly break up a surface slick into micron-sized droplets that move into thewater column. This provides naturally occurring oil degrading bacteria greateraccess to the oil by creating a dilute mixture of oil-in-water rather than athick surface accumulation. Fortunately, oil degrading bacteria are present inall marine environments, having evolved to degrade oil released by naturalseeps (Margesin and Schinner, 2001; Prince and Clark, 2004). Dispersed oil rapidly dilutes (French McCay and Payne, 2001; French McCay etal., 2006; McAuliffe et al., 1980; Cormack and Nichols, 1977; Daling andIndrebo, 1996), and concentrations above known toxicity thresholds do notpersist for more than a few hours after effective dispersant application. Thusthe potential for acute impacts to the environment from dispersed oil islimited in duration and space. In contrast, a surface slick has the potentialto impact marine mammals and birds for many days and strand on sensitiveshorelines. The most sensitive areas in many marine environments are marinemarshes and swamps. These areas can take years to decades to recover (Sell etal., 1993) once impacted by surface slicks.
Abstract Oil spill dispersants (OSD) are known to be efficient tools needed to clean and disperse many oil spills. Dispersants are used to disperse oil and prevent them from reaching the shorelines. There are two major concerns in the use of dispersants on our environment. Their toxicity, because the synergistic toxicity effects of these chemicals is of great concern as different chemicals that combine together in the same effluent can have toxic effects even when each of the individual chemicals is known to be non-toxic. Also their biodegradability, as every product whose final fate is in our environment should biodegrade quickly in order to avoid irreparable damage and disruption of the natural ecosystem. This work reviewed literature on oil spill dispersants from 1994–2014 focusing on their toxicity and biodegradability. From the review, many researchers however reported that dispersed oil is more toxic than the crude oil while very few were able to show that the dispersed oil was less toxic or equal in toxicity to the crude oil. They also showed that the dispersant increased the concentration of PAHs in the water column, this some accredited to be the cause of the increased toxicity. The effect of the toxicity on the various organs of the organism was noted as some recorded lesions on the gills of fish, drop in heart rate and so on. Many studies proved that dispersants do actually increase the biodegradability although to some it was restricted to some components of the crude oil. Some researchers however showed that the dispersant reduced the biodegradability of the crude oil. Also noted was the fact that various crude oils reacted differently when mixed with a dispersant and aquatic organisms reacted differently to different combinations of the dispersed oil. Temperature was shown to play a role in rate of biodegradability. More work needs to be done here in Nigeria to determine the cumulative impact oil spill dispersants have on the different organisms in the ecosystem when mixed with our various crude oils. Since the window of opportunity for use of a dispersant after an oil spill is recorded to be between hours to 2 days, this will aid timely decision making on the use of dispersants in our waters.
The biological damage that resulted from the use of `dispersants' during the `Torrey Canyon' oil spill (1967) indicated that the early dispersants were highly toxic and, perhaps. caused more damage than the oil alone. Despite subsequent improvements in the formulation of dispersants considerable apprehension at their use has persisted. with a number of governments placing severe restrictions on their use.
This apprehension is based largely on concerns about the toxicity of dispersants and consequently this has been much researched. Unfortunately, interpretation of some of the resulting data is difficult This is due to the lack of uniformity in experimental procedures, and also to difficulties in using toxicity data to procedures, and also to difficulties in using toxicity data to determine the effect that dispersants and oil may have on coastal or inshore communities.
There is little information on the effect, and behaviour, of dispersed oil in the marine environment and this is particularly true when we consider long term effects and community recovery.
This paper reviews the information that is available from field and laboratory studies and challenges the validity of some entrenched attitudes to dispersants. Decisions regarding dispersant use must be made in consideration of a range of priorities and protection of one sensitive habitat may entail additional risk to another. Site specific priorities must by identified and options for dispersion considered with reference to all possible spill control strategies.
The `Torrey Canyon' oil spill of 1967, in many ways, set our attitudes towards oil as a pollutant and in particular, spill management and cleanup. Oil on the high seas was widely perceived as a major environmental threat, and a series of well perceived as a major environmental threat, and a series of well publicized `disasters' since then have ensured that crude oil has publicized `disasters' since then have ensured that crude oil has maintained its status as the premier marine pollutant
Partly due to this public exposure, much research has been Partly due to this public exposure, much research has been undertaken on the behaviour, fate, effects and management of oil, both at sea and onshore, and substantial information now exists. In addition, the industry has developed a number of spill prevention measure, procedures, equipment, training and response facilities.
Despite this, spills still occur and management strategies fail, resulting in the, oiling of coastlines and wildlife. On each occasion. contingency plans.
equipment and personnel are examined, faults allocated, and improvements, made wherever possible. Critical assessment certainly occurred after the `Torrey Canyon' incident and one of the most scrutinised aspects was the use of chemical `dispersants' for coastal cleanup. Whenever these were used, biological damage was increased and, chemically cleaned coastlines reportedly. recovered much more slowly than did those that were left alone.
It is important that, whenever possible, these priorities are established before a spill occurs and that contingency plans allow the rapid use of dispersants. if their use is required, through pre-approval. pre-approval. P. 501
Lessard, R.R. (Exxon Research & Engineering Company) | DeMarco, G. (Exxon Research & Engineering Company) | Fiocco, R.J. (Exxon Research & Engineering Company) | Lunel, T. (National Environmental Technology Centre) | Lewis, A. (National Environmental Technology Centre)
Abstract The focus of industry and government activities with respect to oil spills is on prevention. Despite best prevention efforts, however, some spills will occur and industry and government must be fully prepared to respond. After 30 years of studies and practical experience, there is now a definitive body of evidence that the use of dispersants to counter the effects of an oil spill can result in lower overall environmental impact than relying on other countermeasures, and for many large spills, it is often the only practical at-sea response technique. This conclusion is supported by numerous international organizations. A number of countries, including the U.S. have recently become more pro-active in supporting and advocating dispersant use. One major reason for this support has been the development of new dispersants with increased capability and improved toxicity characteristics. This paper focuses on new capability to disperse heavy and/or weathered oils such as bunkers. It summarizes the mechanism by which dispersants work, lists their advantages and reviews the results of recent large-scale field tests in the North Sea which conclusively demonstrated the capability of new products to disperse heavy and weathered oils.