Page 34: of Marine News Magazine (September 2011)

Much of the oil that entered Gulf of Mexico waters from BP's wellhead last year has disappeared from view, though unknown amounts remain near the ocean floor, scientists say. Marshes in a few coastal areas are saturated with oil, however, and cleanup work continues in those spots. Still, remnants of the spill ? tarballs and mats in the surf and an occasional sheen on the water ? have posed no real threat to navigation this summer. NOAA U SESA BUDGETTOEXPLAIN DISAPPEARANCE A share of the spilled oil vanished on its own, without the help of chemical dispersants and skimmers that were used to get rid of it in mid-2010. Last November, the National Oceanic and Atmospheric Administration revised its budget of what happened to BP's spilled oil, and estimated that 23% of it evaporated or dissolved, 17% was directly recovered at the site, 16% was chemi- cally dispersed, 13% dispersed naturally, 5% was burned at sea and 3% was skimmed. Another 23% was classifiedas having disappeared by ?other? means. When asked about evaporation, Doug Helton, NOAA Seattle-based environmental scientist and Incident Operations Coordinator for the agency's Office of Response and Restoration, said ?Hydrocarbon chemicals can dissolve in water. Before oil from the BP well reached the sea surface, some fraction of it had dissolved in the water column, and some of the oil that reached the surface evaporated.? The Macondo well spewed oil into the Gulf from 5,000 feet below the surface. Helton said that various types of oil behave differently. Louisiana's light, sweet crude dissolved in warm Gulf water faster than, for instance, the heavy crude in the 1989 Exxon Valdez accident in Alaska. ?If gasoline in a lawn mower spills onto a driveway, you don't see it the 34MNSeptember 2011GOM Environmental Update BP's Spilled Oil Has Mostly Vanished But Marsh Cleaning Continues ? by Susan BuchananSkimmer in action.(Courtesy U.S. Coast Guard)MN#9 (32-49):MN 2011 Layouts 9/6/2011 12:17 PM Page 34