Four Years After Deepwater Horizon Spill, Tar Balls Continue to Wash Up on Shore

Researchers have analyzed oil-soaked sand patties near the Gulf of Mexico to track oil from the spill.

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National Journal
Marina Koren
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Marina Koren
June 13, 2014, 11:02 a.m.

In salt marshes along the Gulf of Mex­ico, everything’s still com­ing up oil.

Four years after an ex­plo­sion on a BP-op­er­ated Deep­wa­ter Ho­ri­zon drilling rig spewed 210 mil­lion gal­lons of oil in­to the wa­ter, the sub­stance con­tin­ues to wash ashore in the form of tar balls, or oil-soaked sand pat­ties.

How do we know this oil is from this par­tic­u­lar spill? Sci­ent­ists at the Woods Hole Ocean­o­graph­ic In­sti­tu­tion and Bi­gelow Labor­at­ory for Ocean Sci­ences in Maine have de­veloped a tech­nique that can de­tect oil from spe­cif­ic spills years after they hap­pen and re­veal how that oil has changed over time in the sea. Every oil reser­voir has its own spe­cif­ic amounts of bio­mark­ers, which are mo­lecu­lar fossils that sci­ent­ists can use for identi­fy­ing the source of spills, like hu­man fin­ger­prints.

Re­search­ers were able to con­nect the bio­mark­ers found in oil-filled sand clumps, col­lec­ted over a 28-month peri­od, that washed up on shore from the Gulf of Mex­ico near the Deep­wa­ter Ho­ri­zon spill in 2010. Some had de­graded since then, which oc­curs after pro­longed ex­pos­ure to the nat­ur­al en­vir­on­ment.

“These bio­mark­ers are not as re­si­li­ent as once thought, and they may provide a fu­ture win­dow in­to de­term­in­ing how much, and how quickly, these oil com­pon­ents may linger in the en­vir­on­ment when ex­posed to air, sun­light, and the ele­ments,” said Chris Reddy, a sci­ent­ist at the Woods Hole Ocean­o­graph­ic In­sti­tu­tion and a coau­thor of the sand-patty study, pub­lished in the journ­al En­vir­on­ment­al Sci­ence & Tech­no­logy on Thursday.

This kind of tech­nique gives sci­ent­ists an idea of what hap­pens to oil once it hits the high seas — and stays there. Much of the oil from the 2010 spill has either de­graded, evap­or­ated, or been re­moved by hu­mans, and when it reaches shore these days, it doesn’t come in its usu­al li­quid form. “Al­though some Ma­condo [well] ma­ter­i­al does con­tin­ue to be iden­ti­fied, the amounts and fre­quen­cies are much lower than be­fore, which is why it is im­port­ant to dis­tin­guish it from oily ma­ter­i­al from oth­er sources, in­clud­ing the many nat­ur­al seeps in the Gulf,” BP spokes­man Jason Ry­an told Na­tion­al Journ­al.

However, ex­perts say that at least 60 per­cent of oil from the spill re­mains un­ac­coun­ted for in the ocean.

This story has been up­dated.

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