10 May 2010

10 Biggest Oil Spills in History + How Oil Breaks Down in H2O

If the Deepwater Horizon spill in the Gulf of Mexico continues for another month, it may match the Exxon Valdez oil spill of 12 million gallons. But the Exxon Valdez spill does not even make it onto the top 10 list of historical oil spills. And while natural oil seeps spill far more oil every year than the total of all human caused oil spills, nature finds a way to clean up after herself. In fact, nature even cleans up after human-caused oil spills.

1. Gulf War, 1991
Location: Kuwait
Gallons: 240 to 336 million

2. Ixtoc 1 Oil Well, 1979
Location: Bay of Campeche, Mexico
Gallons: 140 million

3. Atlantic Empress, 1979
Location: Trinidad and Tobago, West Indies
Gallons: 88.3 million

4. Fergana Valley, 1992
Location: Uzbekistan
Gallons: 87.7 million

5. Nowruz Oil Field, 1983
Location: Persian Gulf
Gallons: 80 million

6. ABT Summer, 1991
Location: Off the coast of Angola
Gallons: 80 million

7. Castillo de Bellver, 1983
Location: Off Saldanha Bay, South Africa
Gallons: 78.5 million

8. Amoco Cadiz, 1978
Location: Off Brittany, France
Gallons: 68.7 million

9. Odyssey Oil Spill, 1988
Location: 700 nautical miles off the coast of Nova Scotia, Canada
Gallons: 43 million

10. M/T Haven Tanker, 1991
Location: Genoa, Italy
Gallons: 42 million


Here's how nature cleans up after a human oil spill or a natural oil seep:
As soon as oil hits water, the ocean begins its deconstruction. In fact, the marine environment handles oil much like a human body handles alcohol: destroying, metabolizing and depositing the excessive compounds —in oil's case, hydrocarbons—then transforming the compounds into safer substances, says Stanislav Patin, chairman of the Aquatic Toxicology Committee under the Russian Academy of Sciences and international expert on marine pollution.

...The day after it enters the water, chemicals in the oil begin to transform, both at the water's surface and farther into the water column. Trace elements lurking in water can speed or slow the process while the sun fuels the breakdown, decomposing even the most complex of oil's components over time. The warmer the water temperature and the more sun exposure, the faster the oil breaks down.

During the first few days after a spill, between 20 to 40 percent of oil's mass turns into gases, and the slick loses most of its water-soluble hydrocarbons—what's left are the more viscous compounds that slow down the oil's spread across the water.

...Between 10 and 30 percent of the oil is absorbed by sediments and suspended materials and deposited on the bottom of the sea. This generally occurs in coastal zones and shallow waters where water mixes readily and more particles float. Usually, oil drifts in the same direction as the wind, though storms and water turbulence can speed up the spread of the oil. This movement in turn can degrade parts of the oil into separate fragments that spread far away from the initial spill. As these fragments move further offshore and into deeper areas, sediment absorption becomes a much slower process. While sediments latch onto oil components, so do filter feeders and plankton. Planktonic organisms absorb the oil/water mix and dump it at the bottom of the ocean when they excrete other metabolites. Once at the bottom, though, the decomposition rate of the oil halts almost completely because of lack of oxygen, and heavy oil fragments can be preserved inside sediments for years....after a time—with weathering, feasting micro-organisms and solar decomposition—the water self-purifies, as intermediate compounds gradually disappear and water and carbon dioxide reform.... _PM
At the bottom of the food chain, oil-metabolising bacteria thrive on the nasty gunky stuff. Nature has billions of years' experience dealing with oil seeps and natural spills. Oil spills do not leave a permanent trace, because oil is food for many micro-organisms.

Just as CO2 is quickly gobbled up by vast numbers of ocean bacteria, so are hydrocarbons of all types cleared from the oceans and coastlines by bacterial oil gobblers.

Humans will lend a hand, of course. Once the oil gush from the seafloor is stopped, mopping-up efforts will proceed rapidly. Oil will be burned, vacuumed, sopped up with hair-filled panty hose and more futuristic materials such as aerogel. Special bacterial solutions will be added to shorelines to speed up degradation of onshore oil.

But it is nature herself who takes care of most of the problem -- as she has for billions of years.


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