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Report on Comparison of Ecosystem Exposure Resulting from Various Response Scenarios Including Tested Software and User's Guide2004 Research Abstracts - Table of Contents National Exposure Research Laboratory - FY04 Research AbstractScientific Problem and Policy IssuesOil spills can cause widespread environmental contamination and damage to shorelines, wildlife and resources. There is a universal desire to minimize this damage through various response approaches. One approach is to use chemical dispersing agents–dispersants--to prevent shoreline and wildlife oiling. The chemical dispersing agent, which consists of mixtures containing surfactants, has the ability to facilitate breakup of an oil slick into droplets that can be dispersed into the water column. The disadvantage of dispersants is that the oil and dispersant may then contaminate the water column and cause harmful effects on fish and other aquatic organisms. Part of the decision-making process regarding dispersant use should include a scientifically defensible assessment of the impact of dispersants. Application of models is limited, however, due to limited data being collected during oil spill responses. Thus, models can provide some insight into oil slick and dispersant behavior, but it is unlikely that all required data will be collected to support their usage. This means that careful evaluation of the uncertainties inherent in use of oil spill models is required, and this uncertainty needs to be factored into the decision-making process. Research ApproachThe impact of dispersants on oil spills is assessed through use of an extensible model development platform (MDP) developed for this project. The MDP consists of graphical user interface components, object-oriented numerical solvers, and a hierarchy of models and data for oil spills. The object-oriented approach was selected, because some features of oil spills align naturally with object-oriented programming - the common splitting of oil slicks into small patches behave in similar ways. Such behavior is ideally suited to the "object" paradigm of this kind of programming. A side benefit is that the models, data and graphical user interfaces can be combined to build the hierarchy of applications. The resulting model is called the EPA Object-Oriented Oil Spill (ERO3S) model. Along with development of the model, there were unmet data needs concerning the behavior of dispersants and the properties and composition of certain crude oils. The project therefore included development of these data to support use of the model. Because the commonly used dispersant formulations are proprietary, the best way to include their interaction with spilled oil is through empirical relationships. These were developed using a new testing protocol developed by ORD for the Oil Spill program. This protocol uses a baffled flask test (BFT) that was adopted for this work. ERO3S contains five separate models, built from a collection of model components and data: 1) empirical dispersant data evaluation, 2) an analytical dispersant model for the laboratory test, 3) a single oil spreading/dispersant application model, 4) a patchy oil slick model that uses components of items 1 and 3, and 5) an uncertainty calculation that incorporates features of items 1, 3, and 4. Each product supporting the development of the model was subjected to peer review prior to publication. Results and ImpactsThe ERO3S model is intended for use by on-scene coordinators and oil spill response planners. Feedback from use of the first version of the model is being gathered and used for revision and enhancement of the model. The benefit of developing an EPA model is that the Agency will have access to a public-domain model wherein all assumptions and limitations of the model are transparent to the Agency. Research Collabortation and Research ProductsThe oil spill modeling has been an in-house, Federal effort that has been augmented by collaboration with outside research groups. These included Environment Canada Emergencies Science and Technology Division, and the University of Cincinnati Department of Civil and Environmental Engineering.
Future ResearchDevelopment of oil spill modeling will continue with emphasis on the multicomponent nature of the oil, transport of dissolved species and droplets and coupling of the model with additional models and data on bathymetry and climatic data. Future development will be coordinated and shaped by interaction with EPA on-scene coordinators and oil spill response planners in the EPA Regional offices. An Internet presentation of the model and its supporting data is in preparation. Contacts for Additional InformationQuestions and inquiries can be directed to:
James W. Weaver, Ph.D. Federal funding for this research was administered under EPA contract numbers 1D-5859-NAFX, 68-W-01-032, and 69-C-00-159. Support for the internal portion of this project was provided through the U.S. EPA's Office of Research and Development, National Exposure Research Laboratory, Ecosystems Research Division. 2004 Research Abstracts - Table of Contents
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