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Oil Spills for Dummies

by Deborah Blum So, at a Sunday news briefing, British Petroleum's CEO, Tony Hayward, announced that there are no underwater plumes of oil resulting from the April accident at the company's Deepwater Horizon rig in the Gulf of Mexico.

Why? Well, first BP's testing hasn't found any such evidence. And second, Hayward reminds us that, you know, oil floats. Or if we didn't get that: "Oil has a specific gravity that's about half that of water. It wants to get to the surface because of the difference in specific gravity."

Let's give the man this: there is definitely oil floating on the surface waters of the Gulf of Mexico. Actually - as this photo featured on MSNBC demonstrates - it's kind of hard to miss"

But also let's look past the Oil Spills For Dummies approach regarding those underwater plumes. Because Hayward, as it turns out, refused to give any information about the BP water analysis that found no evidence of oil plumes beneath the surface.

This despite the fact that independent researchers from at least four universities have identified underwater plumes of oil using research boats, submersible vehicles, and even sending divers into the plumes. The University of South Florida reported a plume of near transparent, oil-infused water stretching some 20 miles from the site of the oil ring. Similar results have been reported by the researchers from the University of Georgia, the University of Missippippi, and Louisiana State University.

Although maybe he was just trying counter the sense of depression that seems to be resulting from those encountering underwater plumes? "Every fish and invertebrate contacting the oil is probably dying. I have no doubt about that," Prosanta Chakrabarty, a Louisiana State University fish biologist, told the Associated Press.

If so, it would have been helpful if he would been a little more careful of his facts - or at least made the assumption that we were smart enough to vet them. Because as it turns out, deep water physics tell us that oil leaks coming from about a mile below the surface - as with the Deepwater Horizon - actually don't come so readily to the surface.

That's because at greater depths, under greater pressure, water acquires greater density. In fact, this increased density of water can achieve a kind of equality with the naturally buoyant hydrocarbons in oil. Scientists call this a neutral buoyancy state and what it means is that instead of floating to the surface, the pressures exerted in deep water cause the oil to mix instead into subsurface waters.

But beyond the physics of deep water spills, BP itself may also be creating these underwater plumes by its heavy use of chemical dispersants to break up the slick of oil on the surface. As countless studies show, as dispersants break the oil into tiny particles, those the fragments tend to sink below the surface where - if all goes to plan - they are engulfed by oil-digesting microbes and degraded into more harmless materials.

As one industry group, the International Tankers Association, states: "If dispersion is successful, a characteristic brown plume will spread slowly down from the water surface a few minutes after treatment."

The creation of dispersed oil plumes isn't exactly a secret to our government either. For instance, here's a handy document created by our own National Oceanic and Atmospheric Administration (NOAA): The Dispersant Application Observer Job Aid. And - surprise - it includes includes photo after photo of plumes created by spraying disperant onto surface oil.

None of these are as stark as the photo of oil oozing across the wave-tossed surface of the Gulf. In fact, the image provided by the tanker association is rather beautiful:

But you can see in it the white cloud of dispersant, which has not touched oil, in the water and the shadowy plumes forming under the darker oil slicked on the surface, where the dispersant has done its job. And you do have to wonder, don't you? At least, I wonder how dumb Mr. Hayward thinks we are.

Of course, he also declared that the fisherman reporting illnesses after cleaning duty in the Gulf were just suffering from food poisoning. Hands up if you believe that one.

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Tagged in: Gulf Oil Spil



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