WASHINGTON — Dispersants injected deep in the Gulf of Mexico to counter an oil gusher last spring seemed to keep some oil from fouling the water's surface, but the chemicals lingered underwater, raising concerns about long-term problems, a new study found.
The first extensive research into what happened to 770,000 gallons of dispersants used a mile deep near the busted BP well found a mixed bag of results. The new research appears in the journal Environmental Science & Technology and focused on the fate of the controversial chemicals rather than their toxicity.
Scientists at the Woods Hole Oceanographic Institution in Massachusetts found circumstantial evidence that the chemicals guided some oil into underwater currents, stopping it from bubbling up to the surface, where it would do more damage, said marine chemist Elizabeth Kujawinski.
That would be considered a good thing, keeping marshes and beaches from getting more tarred, Kujawinski said.
But she added, "the dispersant is sticking around," which is worrisome. The chemicals didn't seem to biodegrade the oil and gas as fast as basic chemistry would predict. Her study said the key chemicals in dispersants underwent "negligible or slow rates of biodegradation." Other studies have found that the oil – not the dispersant – broke apart quickly.
How fast chemicals degrade is important because of potential long-term damage from chronic contamination, she said.
And when it comes to the basic question of whether using the dispersants worked, Kujawinski said it is still too early to tell.
Larry McKinney, who directs a Gulf of Mexico research center at Texas A&M University in Corpus Christi, said the government's use of the chemicals was "successful in avoiding the most serious damage to wetlands marshes. That did work. But there's likely a price to be paid for that success."
A federal study last year found that in the short term, dispersant is no more dangerous to aquatic life than oil. However, the long-term effects to aquatic life remain unknown.
The new study illustrates how little scientists know about using dispersants in deep water, said Florida State University marine scientist Ian MacDonald.