Just when the Deepwater Horizon oil spill was beginning to seem like old news, a new study reveals that the chemical dispersants used against the oil are lingering longer than expected. What the long-term implications of that will be, exactly, is unclear, but it researchers say the chemicals are not degrading as rapidly as it was first believed.
About 771,000 gallons of dispersant was injected near the sea floor, directly into the oil flow. Researchers monitored one specific component of the dispersant, an anionic surfactant called dioctyl sodium sulfosuccinate, or DOSS, which made up about 10% of the total dispersant. Measuring DOSS at the time of the injection and again a couple of months after dispersant was applied, they found very little biodegradation of the chemical. It had, however, dispersed as the plume drifted away from the wellhead, so that instead of being present in parts per million when applied, it is now detected in the parts-per-billion range.
At these concentrations, DOSS is not toxic to coastal organisms like blue crab. But there has been no research on its effects on the deep sea ecosystem—on deepwater fish, corals, and other organisms—or on the effects of very long-term exposure. It’s possible that deep sea organisms might be either more or less sensitive than the coastal organisms on which studies have actually been done, and the authors of the study call for further research.
The study was published online in January in the American Chemical Society journal Environmental Science & Technology. You can read the abstract here and a summary of the study here.