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A beach after an oil spill
An oil spill is the release of a liquid petroleum hydrocarbon into the environment due to human activity, and is a form of pollution. The term often refers to marine oil spills, where oil is released into the ocean or coastal waters. The oil may be a variety of materials, including crude oil, refined petroleum products (such as gasoline or diesel fuel) or by-products, ships\' bunkers, oily refuse or oil mixed in waste. Spills take months or even years to clean up.
Oil is also released into the environment from natural geologic seeps on the sea floor. http://seeps.geol.ucsb.edu/ Most man-made oil pollution comes from land-based activity, but public attention and regulation has tended to focus most sharply on seagoing oil tankers. [1]
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Studies of the Exxon Valdez oil spill have shown that the environmental damage caused by oil spills can be greater than was previously thought. Petroleum-based hydrocarbons can negatively impact marine life at concentrations as low as one part per billion.Long-Term Ecosystem Response to the Exxon Valdez Oil Spill, Science, v.302, 19 December 2003, pp.2082-2085
Birds killed as a result of oil from the Exxon Valdez spill
The lighter fractions of oil, such as benzene and toluene, are highly toxic, but are also volatile and evaporate quickly.[citation needed] Heavier components of crude oil, such as polycyclic aromatic hydrocarbons (PAHs) appear to cause the most damage. While they are less toxic than the lighter volatiles, they persist in the environment much longer. A heavy oil spill can also blanket estuaries and shoreline ecosystems such as salt marshes and tidal pools, preventing gas exchange and blocking light. The oil can mix deeply into pebble, shingle or sandy beaches, where it may remain for months or years.
Seabirds are severely affected by spills. The oil penetrates and opens up the structure of their plumage, reducing its insulating ability, and so making the birds more vulnerable to temperature fluctuations and much less buoyant in the water. It also impairs birds\' flight abilities, making it difficult or impossible to forage and escape from predators. As they attempt to preen, birds typically ingest oil that coats their feathers, causing kidney damage, altered liver function, and digestive tract irritation. This and the limited foraging ability quickly causes dehydration and metabolic imbalances. Most birds affected by an oil spill die unless there is human intervention.Dunnet, G., Crisp, D., Conan, G., Bourne, W. (1982) "Oil Pollution and Seabird Populations [and Discussion]" Philosophical Transactions of the Royal Society of London. B 297(1087): 413–427Untold Seabird Mortality due to Marine Oil Pollution, Elements Online Environmental Magazine.
Marine mammals exposed to oil spills are affected in similar ways as seabirds. Oil coats the fur of Sea otters and seals, reducing its insulation abilities and leading to body temperature fluctuations and hypothermia. Ingestion of the oil causes dehydration and impaired digestion.
Volunteers cleaning up the aftermath of the Prestige oil spill
a One tonne of crude oil is roughly equal to 308 US gallons, or 7.33 barrels.
By observing the thickness of the film of oil and its appearance on the surface of the water, it is possible to estimate the quantity of oil spilled. If the surface area of the spill is also known, the total volume of the oil can be calculated.Metcalf & Eddy. Wastewater Engineering, Treatment and Reuse. 4th ed. New York: McGraw-Hill, 2003. 98.
| Film Thickness | Quantity Spread | |||
|---|---|---|---|---|
| Appearance | in | mm | gal/sq mi | L/ha |
| Barely visible | 0.0000015 | 0.0000380 | 25 | 0.370 |
| Silvery sheen | 0.0000030 | 0.0000760 | 50 | 0.730 |
| First trace of color | 0.0000060 | 0.0001500 | 100 | 1.500 |
| Bright bands of color | 0.0000120 | 0.0003000 | 200 | 2.900 |
| Colors begin to dull | 0.0000400 | 0.0010000 | 666 | 9.700 |
| Colors are much darker | 0.0000800 | 0.0020000 | 1332 | 19.500 |
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This section needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (December 2007) |
A sheen is usually dispersed (but not cleaned up) with detergents which makes oil settle to the bottom. Oils that are denser than water, such as Polychlorinated biphenyls (PCBs), can be more difficult to clean as they make the seabed toxic.
Clean-up efforts after Exxon Valdez oil spill.
Methods for cleaning up include:
Equipment used includesEmergency Response: Responding to Oil Spills. Office of Response and Restoration. National Oceanic and Atmospheric Administration (2007-06-20).:
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