On the surface, it appears that the dispersants used to break up the 200 million gallons of oil spilled following the Deepwater Horizon explosion of 2010 did their job.
(From Gainesville.com / by Jeff Schweers) — But a team of researchers from the University of Florida and three other universities detected that a residual “ghost signature” of oil still remained two years after the spill and after other researchers found no discernible trace of hydrocarbons in the Gulf of Mexico.
“It’s really helpful to see how long these chemicals persist,” said Thomas Bianchi, who holds the Jon and Beverly Thompson Endowed Chair of Geological Sciences at UF. The findings were published in the August issue of Environmental Science and Technology.
Whether those traces are harmful in the long term will be the focus of a future study, he said.
The Deepwater Horizon explosion killed 11 workers and discharged millions of gallons of oil and gas from a depth of 5,000 feet, spreading over 491 miles of coastline. In the six months following the spill, some 8,000 birds, fish and other wildlife were found dead.
Scientists have been conducting research for years to determine the full extent of the damage caused by the spill. Much of that research has been funded by BP, the National Oceanic Atmospheric Administration and the Gulf of Mexico Research Initiative.
Funded by BP and the GMRI, Bianchi and his colleagues analyzed water samples taken from 900 to 1,100 meters deep in 2012 and found a leftover residue that had blended into the natural carbon pool. Until then, all the analysis using standard methods had found no evidence of hydrocarbons.
“Basically, the contaminants can be degraded into a form we no longer recognize and transferred into the natural surroundings,” he said. “Classic hydrocarbons … are not what we’re finding.”
Instead, they found degraded fluorescent compounds using fluorometers, shining a light on the samples in a lab to pick up flashes of luminescence.
“Many molecules fluoresce, like benzene,” Bianchi explained. They have a ring structure that comes from hydrocarbons, he said, which enabled them to “dust” for the chemical fingerprints that showed evidence of hydrocarbons in the samples.
BP is working to develop a map of the background level of naturally occurring molecules, he said.
More work is necessary to determine if the residue poses a danger to the environment and to Gulf wildlife, Bianchi said. He said he wants to use ultra-high resolution spectrometry to analyze the details of the compound for potential dangers.
“The real takeaway here is that once you no longer detect dangerous chemicals you don’t close the books and move on,” Bianchi said. “Those residual ghost signatures remain.”
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