A chemical analysis indicates that the source of oil sheens recently found floating at the ocean's surface near the site of the Gulf of Mexico Deepwater Horizon oil spill is pockets of oil trapped within the wreckage of the sunken rig.
First reported to the U.S. Coast Guard by multinational oil and gas company BP in September 2012, the oil sheens raised public concern that the Macondo well, which was capped in July 2010, might be leaking.
However, both the Macondo well and the natural oil seeps common to the Gulf of Mexico were confidently ruled out, according to researchers from the University of California Santa Barbara (UCSB) and the Woods Hole Oceanographic Institution (WHOI).
The results are published this week in the journal Environmental Science & Technology.
"Silver linings in the dark cloud of the Deepwater Horizon spill are very hard to come by," says Don Rice, program director in the National Science Foundation's (NSF) Division of Ocean Sciences, which funded the research.
"Among the precious few are the lessons we've learned about the marine biogeochemistry of petroleum mixtures. This team has demonstrated convincingly that we can also use what we have learned for forensic purposes."
The researchers used a recently patented method to fingerprint the chemical makeup of the oil sheens, and to estimate the location of the source based on the extent to which gasoline-like compounds evaporated from the sheens.
"The results demonstrate a recently developed geochemical analytical method and may have real-world implications in environmental management strategies for future contamination incidents," says Deborah Aruguete, program director in NSF's Division of Earth Sciences, which co-funded the research.
Because every oil sample contains chemical clues pointing to the reservoir it came from, scientists can compare it to other samples to determine if they share a common source.
"This appears to be a slow leak from the wreckage of the rig, not another catastrophic discharge from a deep oil reservoir," says geochemist David Valentine of UCSB.
"Continued oil discharge to the Gulf of Mexico from the wreckage of the Deepwater Horizon rig is not a good thing, but there is some comfort that the amount of leakage is limited to the pockets of oil trapped within the wreckage of the rig."
Read the full story at PhysOrg>>
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