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  • Dick writes about Earth and planetary science for Science magazine.
 

Mother Nature Having Her Way With Gulf Oil

4 August 2010 1:27 pm
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Fully three-quarters of the estimated 4.9 million barrels of oil that spewed from BP's Macondo well in the Gulf of Mexico bypassed efforts to collect it or burn it off, according to a government report released Wednesday morning. The bulk of the spill evaporated, dissolved into seawater, drifted onto beaches, or remains dispersed beneath the surface. Offshore, at least, it is rapidly being broken down by oil-eating microbes.

Only a third of the spilled oil was removed or chemically dispersed. Catching it at the wellhead prevented 17% from entering the environment. Burning at the surface removed 5%, and skimming caught 3%. The controversial use of dispersants to emulsify the oil and therefore accelerate its natural degradation managed to disperse 8% of the oil. That made for a total of 33% of the oil that was dealt with by responders.

Natural processes removed or dispersed about 41% of the spilled oil, according to the report. A quarter evaporated into the atmosphere or dissolved in seawater. Sixteen percent dispersed into microscopic droplets as it blasted from the wellhead. That left 26% on the surface as sheen or tarballs, washed ashore, or buried in shoreline sand and sediments. The 50% of the spill that remains in the gulf or on the shore, the report emphasizes, is being degraded naturally. NOAA has graphed these figures in a pie chart

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