Gulf spill study shows long-term toxic effect of dispersants

WASHINGTON - A new study from the Woods Hole Oceanographic Institution examines the impact the deep-water residue of oil and dispersant-which some say has its own toxic effects-might have had on environment and marine life in the Gulf.

Last year, nearly 800,000 gallons of chemical dispersant were injected directly into the oil and gas flow in an attempt to break up the oil droplets.

“We don’t know if the dispersant broke up the oil,” said Elizabeth B. Kujawinski

“We found that it didn’t go away, and that was somewhat surprising.”

Kujawinski and her colleagues found one of the dispersant’s key components, called DOSS (dioctyl sodium sulfosuccinate), was present in May and June-in parts-per-million concentrations-in the plume from the spill more than 3,000 feet deep.

According to the team, the concentrations of DOSS indicate that little or no biodegradation of the dispersant substance had occurred.

They found further evidence that the substance did not mix with the 1.4 million gallons of dispersant applied at the ocean surface and appeared to have become trapped in deepwater plumes of oil and natural gas reported previously by other WHOI scientists and members of this research team.

The team also found a striking relationship between DOSS levels and levels of methane, which further supports their assertion that DOSS became trapped in the subsurface.

David Valentine of UC Santa Barbara and a co-investigator in the study, said, “The results indicate that an important component of the chemical dispersant injected into the oil in the deep ocean remained there, and resisted rapid biodegradation.”

“This knowledge will ultimately help us to understand the efficacy of the dispersant application, as well as the biological effects.”

Kujawinski cautioned that “we can’t be alarmist” about the possible implications of the lingering dispersant. Concentrations considered “toxic” are at least 1,000 times greater than those observed by Kujawinski and her colleagues, she said.

“The decision to use chemical dispersants at the sea floor was a classic choice between bad and worse,” Valentine said.

“And while we have provided needed insight into the fate and transport of the dispersant we still don’t know just how serious the threat is; the deep ocean is a sensitive ecosystem unaccustomed to chemical irruptions like this, and there is a lot we don’t understand about this cold, dark world.”

“The good news is that the dispersant stayed in the deep ocean after it was first applied,” Kujawinski says. “The bad news is that it stayed in the deep ocean and did not degrade.”

The study appears online Jan. 26 in the American Chemical Society (ACS) journal Environmental Science and Technology. (ANI)