Gulf oil spill: Tests confirm oil is light grade

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Experts working to control the Gulf of Mexico oil slick got one piece of good news Tuesday: Tests on new samples appear to show that the material is typical Louisiana sweet crude, a light oil that can be either burned or readily dispersed.

Such oil is highly prized because it contains a high percentage of volatile components that can be used for producing gasoline and other industrial chemicals.

A preliminary test Friday on the first sample from the slick performed by environmental scientist Edward B. Overton of Louisiana State University appeared to show that the oil contained a higher-than-expected concentration of asphalt and other nonvolatile components.

Such materials are extremely resistant to degradation in the environment, which is why they are used to construct roads. They also are resistant to burning and extremely difficult to clean up once they reach the shore.


But Overton now thinks that the first sample he received may have been contaminated. “I was alarmed, but now I am a lot less alarmed,” he said Tuesday. “But we still don’t know much about it. We need 40 to 50 samples,” not the four or five that they already have.

A thin layer of oil floating on the surface of water reflects more light than the water itself, creating a rainbow effect when viewed at the proper angle. It is thus called a sheen, much like shiny hair is said to have a sheen. A heavy layer of oil tends to be less reflective than a thinner layer. The more the oil spreads from the wellhead, the thinner it becomes.

-- Thomas H. Maugh II