Burning Off BP Oil Spill Sent 700 Tons of Soot Aloft

BOULDER, Colorado, September 20, 2011 (ENS) – During BP’s three-month-long, five million barrel oil spill last year in the Gulf of Mexico, an estimated one of every 20 barrels of spilled oil was deliberately burned off.

The unified federal response team used controlled burns to remove oil from the open water in an effort to minimize impacts to the shoreline and marine and other wildlife, but burning off the oil fouled the air.

The black smoke that rose from the water’s surface during the controlled burns pumped more than 1.4 million pounds (700 tons) of black carbon pollution, or soot, into the atmosphere, according to new research by researchers at the National Oceanic and Atmospheric Administration’s Cooperative Institute for Research in Environmental Sciences in Boulder, Colorado.

A controlled burn of oil from the Deepwater Horizon/BP oil spill sends towers of fire hundreds of feet into the air over the Gulf of Mexico, June 9, 2010. (Photo by Petty Officer First Class John Masson courtesy USCG)

This amount is roughly equal to the total black carbon emissions normally released by all ships that travel the Gulf of Mexico during a nine-week period, the scientists said.

“Scientists have wanted to know more about how much black carbon pollution comes from controlled burning and the physical and chemical properties of that pollution. Now we know a lot more,” said lead author Anne Perring, a scientist with CIRES and the Chemical Sciences Division of NOAA’s Earth System Research Laboratory in Boulder.

Black carbon is the most light-absorbing airborne particle in the atmosphere and the reason for the black color in the smoky plumes that rise from the surface oil fires. Black carbon can cause warming of the atmosphere by absorbing light.

The study found that the hot soot plumes from the controlled burns reached much higher into the atmosphere than ship emissions normally rise, potentially prolonging the amount of time the black carbon can remain in the atmosphere. The scienitsts said that will affect where the black carbon ends up.

“The size and makeup of the black carbon particles determine how fast the particles are removed from the atmosphere by various processes, which ultimately affects their impact on climate,” says Perring.

Larger particles are removed from the atmosphere more quickly and thus have smaller climate impacts.

Those same properties of black carbon are important for assessing human health impacts. Prolonged exposure to breathing black carbon particles from burning sources is known to cause human health effects.

The polycyclic aromatic hydrocarbons, PAHs, in soot are known mutagens and are classified as a “known human carcinogen” by the International Agency for Research on Cancer.

Perring and her colleagues found that of the oil that was burned, four percent of the mass was released as black carbon, an important metric rarely observed during cleanup of an oceanic oil spill, which could help guide future decision-making.

The researchers also found that the average size of the black carbon particles was much larger than that emitted from other sources in the Gulf region, and that the emitted particles produced were almost all black carbon, unlike other sources such as forest fires that tend to produce other particles along with black carbon.

The new paper, “Characteristics of Black Carbon Aerosol from a Surface Oil Burn During the Deepwater Horizon Oil Spill,” has 15 co-authors from NOAA’s two facilities – the Earth System Research Lab and the Cooperative Institute for Research in Environmental Sciences. It can be found on the “Geophysical Research Letters” website.

For more information about the federal response to the Deepwater Horizon oil spill and ongoing restoration efforts in the Gulf of Mexico, click here.

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