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Mr. Science explains where the oil goes

More Scientific Reality Show Data About the Gulf Spilled Oil

It is hard to do science in sound bites. And newspaper environmental writers don’t win prizes telling good news. So here is a little more about what is really happening to the oil in the Gulf – and there has always been lots of it.

Back on June 20 we here at South East Shipping News explained why oil and water cannot mix. We should have explained that is why kerosene-based dispersants are used to reduce the oil molecules to their smallest sizes, making them easier for microbes to eat or for the sun’s rays to oxidize. Here we go again.

Oil and water

Any substance that carries a net electrical charge, including both ionic compounds and polar covalent molecules can dissolve in water. But oil is a nonpolar molecule. Because there is no net electrical charge across an oil molecule, it is not attracted to water molecules and therefore does not dissolve in water.

Oil floats on or in the water where the effects of marine bacteria and the intense radiation of the sun or the oxidizing effects of sea water break down the carbon bonds, ultimately recycling the oil by biodegradation.

This is why the thousands of small leaks that occur each year from the 4,000 commercial oil platforms operating in the Gulf have no significant impact on the shore and none below the water.

This is also why the 1,500 documented natural seafloor seeps in the Gulf have no significant impact even though they leak about 15 million gallons of oil every year. That is 357,140 barrels-a-year or about 1,000 barrels a day.

Oxygen is an oxidizer

The latest estimates say about 150 million gallons of oil have spilled into the Gulf from the Horizon. Estimates vary, but something like 50 to 100 million gallons of that oil are now dispersed into the water. Bacteria are supposed to "break down" that oil. What does that mean?

It means they will oxidize the oil.

As engineer Iain McClatchie explains it, on average, oil has two hydrogen atoms to one carbon atom. CH2 + 1.5O2 => CO2 + H2O, so consuming 14 grams of oil requires 48 grams of oxygen. So, that means that consuming e.g. 50 million gallons of oil requires 150,000 metric tons of oxygen.

The oxygen concentration of the sea is around 7 mg/kg. So, 150,000 metric tons of oxygen is all the oxygen in 22 cubic kilometers of seawater. 22 cubic kilometers in the Gulf of Mexico is approximately one drop in a 5 gallon bucket.

Bottom line: there is plenty of oxygen, even at depth, to oxidize all the oil spilled.


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