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Oil Spill Dispersants: Efficacy and Effects
process is even more critical for nearshore spills where oil can quickly threaten highly sensitive resources.
Oil spills occur under a very wide range of conditions; thus decisions about appropriate response strategies have to be made for each event. Even for spills that meet pre-approval guidelines for dispersant use, the Federal On-Scene Coordinator (FOSC) has to make a series of decisions to determine whether or not dispersants would be effective and appropriate. Where dispersant use is not pre-approved, many more decisions must be made and the decision-making process becomes that much more difficult. One of the primary objectives of this study was to identify gaps in the information needed to support decisionmaking regarding appropriate use of dispersants. The decision-making framework used most frequently in the United States, and shown in Figure 2-4 in Chapter 2, is used to organize and prioritize the recommendations made in Chapters 3, 4, and 5. Many of the recommendations are relevant to more than one question in the decision-making process, but each recommendation is matched to the question it most strongly supports.
In response to the statement of task, the committee reviewed and evaluated existing information and ongoing research regarding the efficacy and effects of dispersants as an oil spill response technique. The statement of task specifically directed the committee to address “how laboratory and mesoscale experiments could inform potential controlled field trials and what experimental methods are most appropriate for such tests.” All experiments, whether conducted at the bench-top or field scale, represent an attempt to measure or otherwise quantify the contribution of one variable among many that interact to dictate a specific outcome. Depending on the scale of the experiment, many variables may need to be held constant so that the change in outcome can be mapped against variation in a single variable of interest. Unfortunately, this simplification, if not taken under consideration, can reduce the realism of tests to the point that the results are of limited application to real world situations. For example, when bench-top tests are conducted, temperature, salinity, and other natural variables are set and held constant to compare the effectiveness of different dispersants and oil combinations. At the other end of the spectrum, when field tests are carried out, researchers have very limited control over environmental conditions, thus each test result is specific to a narrow set of environmental conditions. If the test is conducted under conditions typical of most spills, some extrapolation is possible; however, spills occur over such a wide range of settings that a relatively large number of tests at a variety of geographic locations would be necessary to identify the range of settings in which the dispersants would be effective. Even if this were possible, many of the most important variables (e.g., concentration of dissolved phase constituents or dispersed oil droplets)