Deepwater Horizon Spill Dispersant Persists in the Environment for Four Years

The 2010 Deepwater Horizon oil spill in the Gulf of Mexico was tragic for thousands. About 210 million gallons of oil gushed from the blown out well into the ocean. In an attempt to prevent this oil from fouling beaches and marshes, British Petroleum (BP) applied 1.84 million gallons of chemical dispersant to the oil. Now, though, researchers have found that this dispersant can persist in the environment for up to four years.

The dispersant compound in question is called DOSS, which decreases the size of oil droplets and hampers the formation of large oil slicks. In this case, the researchers examined samples collected from deep-sea corals and surrounding sediments as well as oil-soaked sand patties found on coastal beaches.

Previously, DOSS had only been analyzed in aqueous samples. Looking for traces in the sand patties was another matter. The researchers used sophisticated instruments to quantify the DOSS in samples.

"We found DOSS persisted in variable quantities in deep-sea coral communities six months after the spill and on Gulf of Mexico beaches 26 to 45 months after the spill," said Helen White, lead author of the new study, in a news release. "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."

Currently, researchers aren't sure what the presence of DOSS could mean for corals and other marine life, but it does point to the fact that this dispersant may need to be used with far more caution in the future.

"It's hard to stay because we don't know how toxic it might be. The EPA has determined what concentrations of DOSS may be harmful to marine life in the water, but the toxicity of DOOS 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."

That said, researchers stress the importance of future studies in order to better understand why dispersant compounds persist in the environment for so long and what impacts they might have on marine life.

The findings are published in the journal Environmental Science & Technology Letters.