Oil from the 1989 Exxon Valdez spill persists in an only slightly weathered form below the surface at some beaches along the Gulf of Alaska after 16 years and may persist for decades, researchers have concluded in a new report. It is scheduled for publication in the Feb. 15 issue of the ACS' Environmental Science & Technology, a semi-monthly journal.
The National Oceanic and Atmospheric Administration's Jeffrey W. Short and colleagues analyzed subsurface oil at 10 beaches, selected at random from among oil-contaminated areas included in their 2001 and 2005 studies.
Earlier research demonstrated that buried oil could retain toxic components for years if buried in anoxic (oxygen-depleted) sediments where little decomposition from weathering occurs. The new study identified a different mechanism in which oil can be preserved in sediments that do contain oxygen. The oil persists because it exists in a thick, emulsified form sometimes termed "oil mousse" that resists weathering.
"Such persistence can pose a contact hazard to inter-tidally foraging sea otters, sea ducks, and shorebirds, create a chronic source of low-level contamination, discourage subsistence in a region where use is heavy and degrade the wilderness character of protected lands," the researchers conclude.
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