Paula Dittrick
OGJ Senior Staff Writer
HOUSTON, Aug. 4 -- Early observations and preliminary research results show most of the oil spilled from the Macondo well is biodegrading quickly, but more research and analysis is needed to determine long-term effects on marine life, a federal science report said.
The National Oceanic and Atmospheric Administration and the US Department of the Interior released a report Aug. 4 outlining measurement methods and best estimates of what happened to the spilled oil. US Environmental Protection Agency scientists also were involved.
More than 25 government and independent scientists contributed to the calculation methods or the calculations. BP PLC, operator of the Macondo well, was not part of the team.
About 33% of the total oil released during the spill was captured or mitigated by burning, skimming, chemical dispersion, and direct recovery from the wellhead. An additional 25% evaporated or naturally dissolved, and 16% was dispersed naturally into microscopic droplets.
The residual amount, estimated at 26%, is either on or just below the water’s surface as residue and weathered tar balls, has washed ashore, or been collected from the shore, or is buried in sand and sediments, the report said.
Dispersed and residual oil remains in the system until it degrades through numerous natural processes, the report said, adding that early indications are that the oil is degrading quickly.
The calculations are based on an estimated 4.9 million bbl of oil released into the gulf. That estimate was released Aug. 2 by the government's Flow Rate Technical Group.
Jane Lubchenco, NOAA administrator, said, "Less oil on the surface does not mean that there isn't oil still in the water column or that our beaches and marshes aren't still at risk. Knowing generally what happened to the oil helps us better understand areas of risk and likely impacts."
It is well known that the warm gulf contains natural bacteria capable of breaking down oil. Other favorable conditions in the gulf are its nutrient and oxygen levels. Scientists also noted that oil enter the gulf through natural seeps.
The oil budget calculations are based on direct measurements wherever possible and the best available scientific estimates where measurements were not possible, the science report said. The numbers for direct recovery and burns were measured directly and reported in daily operational reports.
The skimming numbers were also based on daily reported estimates. The rest of the numbers were based on previous scientific findings, best available information, and a broad range of scientific expertise. These estimates will continue to be refined, Lubchenco said.
Contact Paula Dittrick at [email protected].
US Government Accountability Office.
