One untested hypothesis in oil spill response is that “chemical dispersants do not work effectively in cold water”. This is due to the general misconception that cold water inhibits dispersant effectiveness (DE) and the lack of experimental data to indicate otherwise. To address this issue, the U.S. Minerals Management Service (MMS) funded and conducted two series of dispersant experiments in very cold water at Ohmsett – The National Oil Spill Response Test facility, located in Leonardo, New Jersey from February-March 2006 and January-March 2007. Four Alaskan crude oils Alaska North Slope (ANS), Endicott, Northstar and Pt. McIntyre and two dispersants Corexit 9500 and Corexit 952 7 were used in the test series. The crude oils were tested fresh, weathered by removal of light ends using air sparging and weathered by placing the oils in the tank in both breaking wave conditions and non-breaking wave conditions. Results from the 2006 and 2007 Ohmsett test series demonstrated that both Corexit 9500 and Corexit 9527 dispersants were more than 90% effective in dispersing the fresh and weathered crude oils tested. This verified the results from laboratory and small-scale experiments. MMS believes that results from these test series will assist government regulators and responders in making science based decisions on the use of dispersants as a response tool for oil spills in the Arctic. The results from the 2006 and 2007 Ohmsett dispersant effectiveness test series dispel the thought that chemical dispersants cannot be effective in cold water.

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