By Janet Raloff
Nearly 3 million liters (some 771,000 gallons) of a chemical dispersant ejected into oil and gas from BP’s Deepwater Horizon oil spill last spring and summer lingered until at least September, a new study shows. The chemicals moved in concert with plumes of oil deep beneath the Gulf of Mexico’s surface.
David Valentine of the University of California, Santa Barbara and his colleagues periodically sampled plume water that flowed at depths of 1,000 meters or more between May and September 2010. They shipped these samples to chemist Elizabeth Kujawinski at the Woods Hole Oceanographic Institution in Massachusetts and her colleagues for analysis.
With rare exception, they report online January 26 in Environmental Science & Technology, the dispersant did not degrade but instead moved with the plumes until they were lost to dilution in the Gulf’s depths.
“If the dispersant worked, it should have been associated with the liquid oil — that is, moving off laterally into the deepwater plume. Which is where we found it — and the only place,” Kujawinski says. “We did not see it below the plume or even sloughing off the top of it.”