deepwater horizon
July 17, 2014

Oil Dispersant Still Found In The Gulf Of Mexico Four Years After Deepwater Horizon Spill

Brett Smith for - Your Universe Online

When the Deepwater Horizon released about 210 million gallons of oil into the Gulf of Mexico in 2010, 1.84 million gallons of chemical dispersants were pumped into the Gulf to break up the oil and eliminate oil slicks across the surface of the water.

Now, researchers from Haverford College and Woods Hole Oceanographic Institution (WHOI) have found evidence that the chemical dispersant used, called DOSS, is still in the Gulf ecosystem four years later, according to a new report in the journal Environmental Science & Technology Letters.

The new study is based on analyses of deep-sea corals and sediments gathered in Dec. 2010 – as well as oil-drenched sand patties seen on coastal beaches since July 2010.

“We found DOSS persisted in variable quantities in deep-sea coral communities 6 months after the spill and on Gulf of Mexico beaches 26 to 45 months after the spill,” said study author Helen White, an assistant professor of chemistry with Haverford College. “These results indicate that the dispersant, which was thought to undergo rapid degradation in the water column, remains associated with oil in the environment and can persist for around four years.”

The results of the new study are consistent with those found as a result of earlier research conducted by study author Elizabeth Kujawinski, a marine chemist at WHOI.

“The deep sea is cold and dark and the degradation of dispersant components happens much more slowly under these conditions,” Kujawinski said. “The interesting thing is that the sand patties we’re finding on beaches four years after the spill have DOSS in them. That was somewhat unexpected.”

WHOI researchers have been tracking Gulf beaches for oiled samples since the time of the spill. The work is part of an endeavor to get as much information on the geographical and temporal dispersal of the patties.

In the study, researchers designed a technique to isolate the DOSS from the sand patties. Before this research, dispersant was only examined in aqueous samples. In the lab at WHOI, scientists used advanced instruments to measure the DOSS in samples gathered from environments recognized to contain oil left over from the 2010 oil spill.

“The amounts we detected are quite small, but we’re finding this compound in locations where we expected the dispersants to disappear, either by dissolving in water or by being degraded by bacteria,” Kujawinski said.

The study team said they could only speculate on the long-term effects DOSS persistence has on marine life or for frequent beach goers.

“The EPA has determined what concentrations of DOSS may be harmful to marine life in the water, but the toxicity of DOSS in solid (non-aqueous) forms like sediments or sand patties is not known,” said White. “We know that if you measure ‘x’ amount of this compound in ‘y’ amount of water, that’s toxic. But you can’t compare those numbers to what we’ve found in the sand patties because we’re looking at this compound in a mixture of sand and oil.”

The researchers said future work should focus on learning why DOSS persists in coastal environments – where temperatures are relatively high year-round and there is significant exposure to radiation from the sun.

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