Analyzing samples from the Macondo well and those they collected from the plume in June 2010 aboard the research vessel Endeavor, the researchers found that BTEX represented about 2 percent of the oil that came out of the well, but "nearly 100 percent of what was in the plume," Reddy said.
"A small, selective group of compounds took a right-hand turn" after exiting the well and formed the 3,000-foot-deep plume, he added.
This raises a number of questions, he said, including, "Why are those chemical there in those concentrations? Why are they so abundant in the water?"
The answers have to do with the tendency of those chemicals that "like" to dissolve in water to migrate to the plume, Reddy said.
Unlike other substances emanating from the well that degrade or evaporate in the water or at the surface, the compounds in the plume showed little evidence of biodegrading when the researchers examined the plume in June 2010.
"[O]il and gas experienced a significant residence time in the water column with no opportunity for the release of volatile species into the atmosphere," the researchers reported.
"Hence water-soluble petroleum compounds dissolved into the water column to a much greater extent than is typically observed for surface spills."
"We needed to have an 'end-member' sample, so that we could compare how nature affected the hydrocarbons as they left the riser pipe," Reddy said.
"So this story is really about, 'From pipe to plume: what chemicals got off the elevator to the surface and migrated to the plume.'"
The findings have "direct implications for the ecotoxicological impact of plumes," Reddy said. "Now that we know the compounds were there for a certain time, we need to look at what
|Contact: Cheryl Dybas|
National Science Foundation