Oil spill

An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially marine areas, due to human activity, and is a form of pollution. The term is mostly used to describe marine oil spills, where oil is released into the ocean or coastal waters. Oil spills may be due to releases of crude oil from tankers, offshore platforms, drilling rigs and wells, as well as spills of refined petroleum products (such as gasoline, diesel) and their by-products, heavier fuels used by large ships such as bunker fuel, or the spill of any oily refuse or waste oil. Another significant route by which oil enters the marine environment is through natural oil seeps.^[1]

Oil spills can be controlled by chemical dispersion, combustion, mechanical containment, and/or adsorption. Spills may take weeks, months or even years to clean up.^[2]

Contents 1 Environmental effects 2 Cleanup and recovery 2.1 Prevention 3 Environmental Sensitivity Index (ESI) mapping 3.1 Shoreline type 3.2 Biological resources 3.3 Human-use resources 4 Estimating the volume of a spill 5 Largest oil spills 6 See also 7 References 8 Further reading

Environmental effects

The oil penetrates into the structure of the plumage of birds and animals, reducing its insulating ability, thus making the birds more vulnerable to temperature fluctuations and much less buoyant in the water. It also impairs or disables birds' flight abilities to forage and escape from predators. As they attempt to preen, birds typically ingest oil that covers their feathers, causing kidney damage, altered liver function, and digestive tract irritation. This and the limited foraging ability quickly causes dehydration and metabolic imbalances. Hormonal balance alteration including changes in luteinizing protein can also result in some birds exposed to petroleum.^[3]

Most birds affected by an oil spill die unless there is human intervention.^[4][5] Some studies have suggested that, even after cleaning, less than 1% of oil soaked birds survive.^[6], though it can also exceed 90% as in the case of the Treasure oil spill.^[7] Heavily furred 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 digestions. Because oil floats on top of water, less sunlight penetrates into the water, limiting the photosynthesis of marine plants and phytoplankton. This, as well as decreasing the fauna populations, affects the food chain in the ecosystem. There are three kinds of oil-consuming bacteria. Sulfate-reducing bacteria (SRB) and acid-producing bacteria are anaerobic, while general aerobic bacteria (GAB) are aerobic. These bacteria occur naturally and will act to remove oil from an ecosystem, and their biomass will tend to replace other populations in the food chain. Oil may also cause the death of an animal by entering the animal’s lungs or liver. The animal will then be poisoned by the oil. Oil also can kill an animal by blinding it, and leaving it defenseless.

Cleanup and recovery

Cleanup and recovery from an oil spill is difficult and depends upon many factors, including the type of oil spilled, the temperature of the water (affecting evaporation and biodegradation), and the types of shorelines and beaches involved.^[8]

Methods for cleaning up include:^[9]

• Bioremediation: use of microorganisms^[10] or biological agents^[11] to break down or remove oil.
• Bioremediation Accelerator: Oleophilic, hydrophobic chemical, containing no bacteria, which chemically and physically bonds to both soluble and insoluble hydrocarbons. The bioremediation accelerator acts as a herding agent in water and on the surface, floating molecules to the surface of the water, including solubles such as phenols and BTEX, forming gel-like agglomerations. Undetectable levels of hydrocarbons can be obtained in produced water and manageable water columns. By overspraying sheen with bioremediation accelerator, sheen is eliminated within minutes. Whether applied on land or on water, the nutrient-rich emulsion creates a bloom of local, indigenous, pre-existing, hydrocarbon-consuming bacteria. Those specific bacteria break down the hydrocarbons into water and carbon dioxide, with EPA tests showing 98% of alkanes biodegraded in 28 days; and aromatics being biodegraded 200 times faster than in nature they also sometimes use the hydrofireboom to clean the oil up by taking it away from most of the oil and burning it.^[12]
• Controlled burning can effectively reduce the amount of oil in water, if done properly.^[13] But it can only be done in low wind, and can cause air pollution.^[14]

• Dispersants act as detergents, clustering around oil globules and allowing them to be carried away in the water.^[15] This improves the surface aesthetically, and mobilizes the oil. Smaller oil droplets, scattered by currents, may cause less harm and may degrade more easily. But the dispersed oil droplets infiltrate into deeper water and can lethally contaminate coral. Recent research indicates that some dispersants are toxic to corals.^[16]
• Watch and wait: in some cases, natural attenuation of oil may be most appropriate, due to the invasive nature of facilitated methods of remediation, particularly in ecologically sensitive areas such as wetlands.^[17]
• Dredging: for oils dispersed with detergents and other oils denser than water.
• Skimming: Requires calm waters
• Solidifying: Solidifiers are composed of dry hydrophobic polymers that both adsorb and absorb. They clean up oil spills by changing the physical state of spilled oil from liquid to a semi-solid or a rubber-like material that floats on water. Solidifiers are insoluble in water, therefore the removal of the solidified oil is easy and the oil will not leach out. Solidifiers have been proven to be relatively non-toxic to aquatic and wild life and have been proven to suppress harmful vapors commonly associated with hydrocarbons such as Benzene, Xylene, Methyl Ethyl, Acetone and Naphtha. The reaction time for solidification of oil is controlled by the surf area or size of the polymer as well as the viscosity of the oil. Some solidifier product manufactures claim the solidified oil can be disposed of in landfills, recycled as an additive in asphalt or rubber products, or burned as a low ash fuel. A solidifier called C.I.Agent (manufactured by C.I.Agent Solutions of Louisville, Kentucky) is being used by BP in granular form as well as in Marine and Sheen Booms on Dauphin Island, AL and Fort Morgan, MS to aid in the Deepwater Horizon oil spill cleanup.
• Vacuum and centrifuge: oil can be sucked up along with the water, and then a centrifuge can be used to separate the oil from the water - allowing a tanker to be filled with near pure oil. Usually, the water is returned to the sea, making the process more efficient, but allowing small amounts of oil to go back as well. This issue has hampered the use of centrifuges due to a United States regulation limiting the amount of oil in water returned to the sea.^[18]

Equipment used includes:^[13]

• Booms: large floating barriers that round up oil and lift the oil off the water
• Skimmers: skim the oil
• Sorbents: large absorbents that absorb oil
• Chemical and biological agents: helps to break down the oil
• Vacuums: remove oil from beaches and water surface
• Shovels and other road equipments: typically used to clean up oil on beaches

Prevention

• Secondary containment - methods to prevent releases of oil or hydrocarbons into environment.
• Oil Spill Prevention Containment and Countermeasures (SPCC) program by the United States Environmental Protection Agency.
• Double-hulling - build double hulls into vessels, which reduces the risk and severity of a spill in case of a collision or grounding. Existing single-hull vessels can also be rebuilt to have a double hull.

Environmental Sensitivity Index (ESI) mapping

Environmental Sensitivity Index (ESI) maps are used to identify sensitive shoreline resources prior to an oil spill event in order to set priorities for protection and plan cleanup strategies.^[19][20] By planning spill response ahead of time, the impact on the environment can be minimized or prevented. Environmental sensitivity index maps are basically made up of information within the following three categories: shoreline type, and biological and human-use resources.^[21]

Shoreline type

Shoreline type is classified by rank depending on how easy the garet would be to clean up, how long the oil would persist, and how sensitive the shoreline is.^[22] The floating oil slicks put the shoreline at particular risk when they eventually come ashore, covering the substrate with oil. The differing substrates between shoreline types vary in their response to oiling, and influence the type of cleanup that will be required to effectively decontaminate the shoreline. In 1995, the US National Oceanic and Atmospheric Administration extended ESI maps to lakes, rivers, and estuary shoreline types.^[21] The exposure the shoreline has to wave energy and tides, substrate type, and slope of the shoreline are also taken into account – in addition to biological productivity and sensitivity. The productivity of the shoreline habitat is also taken into account when determining ESI ranking.^[23] Mangroves and marshes tend to have higher ESI rankings due to the potentially long-lasting and damaging effects of both the oil contamination and cleanup actions. Impermeable and exposed surfaces with high wave action are ranked lower due to the reflecting waves keeping oil from coming onshore, and the speed at which natural processes will remove the oil.

Biological resources

Habitats of plants and animals that may be at risk from oil spills are referred to as “elements” and are divided by functional group. Further classification divides each element into species groups with similar life histories and behaviors relative to their vulnerability to oil spills. There are eight element groups: Birds, Reptiles, Amphibians, Fish, Invertebrates, Habitats and Plants, Wetlands, and Marine Mammals and Terrestrial Mammals. Element groups are further divided into sub-groups, for example, the ‘marine mammals’ element group is divided into dolphins, manatees, pinnipeds (seals, sea lions & walruses), polar bears, sea otters and whales.^[21][23] Problems taken into consideration when ranking biological resources include the observance of a large number of individuals in a small area, whether special life stages occur ashore (nesting or molting), and whether there are species present that are threatened, endangered or rare.^[24]

Human-use resources

Human use resources are divided into four major classifications; archaeological importance or cultural resource site, high-use recreational areas or shoreline access points, important protected management areas, or resource origins.^[21][24] Some examples include airports, diving sites, popular beach sites, marinas, natural reserves or marine sanctuaries.

Estimating the volume of a spill

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.^[25]

	Film thickness			Quantity spread
Appearance	in	mm	nm	gal/sq mi	L/ha
Barely visible	0.0000015	0.0000380	38	25	0.370
Silvery sheen	0.0000030	0.0000760	76	50	0.730
First trace of color	0.0000060	0.0001500	150	100	1.500
Bright bands of color	0.0000120	0.0003000	300	200	2.900
Colors begin to dull	0.00004	0.0010000	1000	666	9.700
Colors are much darker	0.0000800	0.0020000	2000	1332	19.500

Oil spill model systems are used by industry and government to assist in planning and emergency decision making. Of critical importance for the skill of the oil spill model prediction is the adequate description of the wind and current fields. There is a worldwide oil spill modelling (WOSM) program.^[26] Tracking the scope of an oil spill may also involve verifying that hydrocarbons collected during an ongoing spill are derived from the active spill or some other source. This can involve sophisticated analytical chemistry focused on finger printing an oil source based on the complex mixture of substances present. Largely, these will be various hydrocarbons, among the most useful being polyaromatic hydrocarbons. In addition, both oxygen and nitrogen heterocyclic hydrocarbons, such as parent and alkyl homologues of carbazole, quinoline, and pyridine, are present in many crude oils. As a result, these compounds have great potential to supplement the existing suite of hydrocarbons targets to fine tune source tracking of petroleum spills. Such analysis can also be used to follow weathering and degradation of crude spills.^[27]

Largest oil spills

Oil spills of over 100,000 tons or 30 million US gallons, ordered by tons^[a]

Spill / Tanker	Location	Date	*Tons of crude oil (thousands)	Barrels (thousands)	US Gallons (thousands)	References
Kuwaiti oil fires [b]	Kuwait	01991-01-17January, 1991 - 01991-11-17November, 1991	&10000000000136000000000136,000-205,000	&100000000010000000000001,000,000-1,500,000	&1000000004200000000000042,000,000-63,000,000	[28]
Kuwaiti oil lakes [c]	Kuwait	01991-01-17January, 1991 - 01991-11-17November, 1991	&100000000000034090000003,409-6,818	&1000000000002500000000025,000-50,000	&100000000010500000000001,050,000-2,100,000	[29][30][31]
Lakeview Gusher	United States, Kern County, California	01910-05-14May 14, 1910 – 02012-09-17September, 1911	&100000000000012000000001,200	&100000000000090000000009,000	&10000000000378000000000378,000	[32]
Gulf War oil spill [d]	Iraq, Persian Gulf and Kuwait	01991-01-19January 19, 1991 - 01991-01-28January 28, 1991	&10000000000000818000000818–1,091	&100000000000060000000006,000–8,000	&10000000000252000000000252,000–336,000	[29][33][34]
Deepwater Horizon	United States, Gulf of Mexico	02010-04-20April 20, 2010 – 02010-07-15July 15, 2010	&10000000000000560000000560-585	&100000000000041000000004,100-4,900	&10000000000172000000000172,000-180,000	[35][36][37][38][39]
Ixtoc I	Mexico, Gulf of Mexico	01979-06-03June 3, 1979 – 01980-03-23March 23, 1980	&10000000000000454000000454–480	&100000000000033290000003,329–3,520	&10000000000139818000000139,818–147,840	[40][41][42]
Atlantic Empress / Aegean Captain	Trinidad and Tobago	01979-07-19July 19, 1979	&10000000000000287000000287	&100000000000021050000002,105	&1000000000008839600000088,396	[43][44][45]
Fergana Valley	Uzbekistan	01992-03-02March 2, 1992	&10000000000000285000000285	&100000000000020900000002,090	&1000000000008778000000087,780	[46]
Nowruz Field Platform	Iran, Persian Gulf	01983-02-04February 4, 1983	&10000000000000260000000260	&100000000000019070000001,907	&1000000000008008000000080,080	[47]
ABT Summer	Angola, 700 nmi (1,300 km; 810 mi) offshore	01991-05-28May 28, 1991	&10000000000000260000000260	&100000000000019070000001,907	&1000000000008008000000080,080	[43]
Castillo de Bellver	South Africa, Saldanha Bay	01983-08-06August 6, 1983	&10000000000000252000000252	&100000000000018480000001,848	&1000000000007761600000077,616	[43]
Amoco Cadiz	France, Brittany	01978-03-16March 16, 1978	&10000000000000223000000223	&100000000000016350000001,635	&1000000000006868400000068,684	[43][46][46][48][49]
MT Haven	Italy, Mediterranean Sea near Genoa	01991-04-11April 11, 1991	&10000000000000144000000144	&100000000000010560000001,056	&1000000000004435200000044,352	[43]
Odyssey	Canada, 700 nmi (1,300 km; 810 mi) off Nova Scotia	01988-11-10November 10, 1988	&10000000000000132000000132	&10000000000000968000000968	&1000000000004065600000040,656	[43]
Sea Star	Iran, Gulf of Oman	01972-12-19December 19, 1972	&10000000000000115000000115	&10000000000000843000000843	&1000000000003542000000035,420	[43][46]
Irenes Serenade	Greece, Pylos	01980-02-23February 23, 1980	&10000000000000100000000100	&10000000000000733000000733	&1000000000003080000000030,800	[43]
Urquiola	Spain, A Coruña	01976-05-12May 12, 1976	&10000000000000100000000100	&10000000000000733000000733	&1000000000003080000000030,800	[43]
Torrey Canyon	United Kingdom, Isles of Scilly	01967-03-18March 18, 1967	&1000000000000008000000080–119	&10000000000000587000000587–873	&1000000000002465400000024,654–36,666	[43][46]
Greenpoint oil spill	United States, Brooklyn, New York City	01940 1940 – 02012-02-171950s	&1000000000000005500000055– 97	&10000000000000400000000400–710	&1000000000001700000000017,000–30,000	[50]

^a One ton of crude oil is roughly equal to 308 US gallons or 7.33 barrels approx.; 1 oil barrel is equal to 35 imperial or 42 US gallons.
^b Estimates for the amount of oil burned in the Kuwaiti oil fires range from 500,000,000 barrels (79,000,000 m³) to nearly 2,000,000,000 barrels (320,000,000 m³). 732 wells were set ablaze, while many others were severely damaged and gushed uncontrolled for several months. The fires alone were estimated to consume approximately 6,000,000 barrels (950,000 m³) of oil per day at their peak. However, it is difficult to find reliable sources for the total amount of oil burned. The range of 1,000,000,000 barrels (160,000,000 m³) to 1,500,000,000 barrels (240,000,000 m³) given here represents frequently-cited figures, but better sources are needed.
^c Oil spilled from sabotaged fields in Kuwait during the 1991 Persian Gulf War pooled in approximately 300 oil lakes, estimated by the Kuwaiti Oil Minister to contain approximately 25,000,000 to 50,000,000 barrels (7,900,000 m³) of oil. According to the U.S. Geological Survey, this figure does not include the amount of oil absorbed by the ground, forming a layer of "tarcrete" over approximately five percent of the surface of Kuwait, fifty times the area occupied by the oil lakes.^[30]
d Estimates for the Gulf War oil spill range from 4,000,000 to 11,000,000 barrels (1,700,000 m³). The figure of 6,000,000 to 8,000,000 barrels (1,300,000 m³) is the range adopted by the U.S. Environmental Protection Agency and the United Nations in the immediate aftermath of the war, 1991–1993, and is still current, as cited by NOAA and The New York Times in 2010.^[51] This amount only includes oil discharged directly into the Persian Gulf by the retreating Iraqi forces from January 19 to 28, 1991. However, according to the U.N. report, oil from other sources not included in the official estimates continued to pour into the Persian Gulf through June, 1991. The amount of this oil was estimated to be at least several hundred thousand barrels, and may have factored into the estimates above 8,000,000 barrels (1,300,000 m³).

See also

Environmental issues with petroleum Environmental issues with shipping List of oil spills LNG spill Low-temperature thermal desorption

National Oil and Hazardous Substances Pollution Contingency Plan Ohmsett (Oil and Hazardous Materials Simulated Environmental Test Tank) Oil Pollution Act of 1990 (in the US) Oil well Penguin sweater

Project Deep Spill, the first intentional deepwater oil and gas spill Pseudomonas putida (used for degrading oil) S-200 (fertilizer) Spill containment Tarball

References

Further reading

• The World Almanac and Book of Facts, 2004
• Oil Spill Case Histories 1967-1991, NOAA/Hazardous Materials and Response Division, Seattle WA, 1992
• Nelson-Smith, Oil Pollution and Marine Ecology, Elek Scientific, London, 1972; Plenum, New York, 1973

Marine pollution Algal bloom Anoxic event Anoxic waters Aquatic toxicology Cultural eutrophication Cyanotoxin Environmental impact of shipping Eutrophication Fish diseases and parasites Fish kill Friendly Floatees Great Pacific Garbage Patch Hypoxia Invasive species Marine debris Mercury in fish Nonpoint source pollution North Atlantic Garbage Patch Nutrient pollution Ocean acidification Ocean deoxygenation Oil spill Particle Plastic particle water pollution Point source pollution Shutdown of thermohaline circulation Stormwater Surface runoff Upwelling Urban runoff Water pollution

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