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Experts: Most of Gulf of Mexico oil spill won't be cleaned up

Despite BP's efforts, only a small percentage of the oil from the Gulf of Mexico oil spill will be cleaned up, say experts.

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Some beaches didn't get cleaned up as much as others, and certain coastal environments (with particular types of sediments and patterns of water flow) tend to hold on to the oil for longer than others. While it can't be seen if you walk along the beach, digging down into the sediments at certain spots can lead to pools of oil that remain in much the same condition as when they first spilled.

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For instance, in 2001, 2003 and 2007, researchers dug over 12,000 pits at dozens of beach sites that had been covered in oil back in 1989. The team found black, oily liquid in over half of the holes dug in 2001.

This subsurface oil was "fingerprinted" back to the Exxon Valdez as the ultimate source (the star-crossed region also had an earthquake-caused oil spill back in 1964). This hidden oil contained the same proportions of polycyclic aromatic hydrocarbons in it as the Exxon Valdez oil collected right at the initial time of the spill. "There was no question we were looking at Exxon Valdez oil," Short, who led the three surveys, told Livescience.

The lingering oil estimate for affected Alaskan beaches stood at 21,000 gallons (80,000 liters) in 2004. This Exxon Valdez oil is decreasing at a rate of 0 to 4 percent per year according to the Exxon Valdez Oil Spill Trustee Council (EVOSTC) – though the lower rate is much more likely – meaning it will take decades or even centuries for the oil to disappear entirely.

Though the lingering oil has broken down, in some locations it remains almost as toxic to the environment as the freshly spilled variety, according to EVOSTC's Web site. (EVOSTC oversees restoration use of civil money to clean up the Sound.)

And even though this leftover oil is "just a teeny fraction of what was originally spilled," Esler said, certain species can still be exposed to it.

Esler and his colleagues used a biomarker that indicates exposure to hydrocarbons (of which oil is one) to look at the potential exposure of harlequin ducks, a particularly vulnerable species, in the area affected by the spill. They found that these ducks were coming into contact with the spilled oil even 20 years after the incident.

Take-home

The findings suggest that oil spills can have an impact on the environment for much longer than previously thought, even decades later.

In the case of the Gulf spill, the oil won't last as long if it stays in open ocean — there it will either evaporate or congeal into clumps and sink to the ocean floor, Esler explained. But if it reaches the coast, it could encounter the types of environments where it can stick around for a long time.

Given the number of places where oil spills have happened and oil has remained even after clean-up efforts, "it's not unreasonable" to think that oil could remain for some time if reaches the Gulf coast, Esler said in a telephone interview Thursday.

The situation at Prince William Sound isn't all bad though, as it seems some species are out of the woods in terms of exposure threats and "there are lots of hints that things are getting better," Esler said.

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