The oil stopped spilling from the Deepwater Horizon wellhead months ago, but the Gulf of Mexico’s environmental saga continues. Researchers have investigated the chemicals used to disperse the oil flow in the first place, and found that these “dispersants” didn’t disperse. The effects of this massive chemistry experiment, however, are still unknown.
“The dispersants got stuck in deep water layers around 3,000 feet [915 meters] and below,” said study leader David Valentine, a microbial geochemist at the University of California, Santa Barbara…. “We were seeing it three months after the well had been capped. We found that all of that dispersant added at depth stayed in the deepwater plumes. Not only did it stay, but it didn’t get rapidly biodegraded as many people had predicted.” [National Geographic]
In total, the response team pumped over 800,000 gallons of dispersants into the oil flow; dispersants break down oil into smaller droplets that can degrade more quickly. But the impact of the dispersants themselves has been up for debate. For the new study, scientists tracked the dispersants by following one of its ingredients: dioctyl sodium sulfosuccinate (DOSS).
What do you get when you mix oil and dispersants? A mixture that doesn’t seem to be more toxic than oil alone, the EPA said yesterday. Their statement came after a second round of testing eight oil dispersants.
The EPA tested the response of two sensitive Gulf species, the mysid shrimp and a small fish called the inland silverside, which they exposed to mixtures of dispersants plus oil and to oil alone.
The results indicate that the eight dispersants tested are similar to one another based on standard toxicity tests on sensitive aquatic organisms found in the Gulf. These results confirm that the dispersant used in response to the oil spill in the Gulf, Corexit 9500A, is generally no more or less toxic than the other available alternatives. [EPA statement]