oil spill
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What is an oil spill?
An oil spill is the release of petroleum into the environment, typically the ocean, due to accidents in oil extraction or transportation. These events can release vast quantities of oil, leading to severe environmental damage, including polluted coastlines, contaminated fisheries, and harm to wildlife. Major causes include equipment failure, human error, and acts of sabotage. Notable incidents include the Deepwater Horizon spill in the Gulf of Mexico and the Persian Gulf War oil spill. Cleanup efforts often involve dispersants, booms, and manual removal, but the long-term ecological impacts can be devastating.
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How can oil spills happen?
Oil spills can occur due to various reasons, primarily related to the extraction and transportation of petroleum. These incidents can stem from accidents involving supertankers, such as collisions or structural failures, leading to the release of large quantities of oil into the water. Leaks can also originate from offshore drilling operations, like the Deepwater Horizon disaster, where equipment failure or explosions can cause significant spills. Furthermore, damage to pipelines, whether from corrosion or external factors like construction, can result in oil seeping into the environment. Industrial activities and natural seepage from the ocean floor also contribute to the overall problem of oil pollution.
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What are the main effects of oil spills on the environment?
Oil spills have devastating effects on marine ecosystems. They can lead to the death of birds, mammals, and sea turtles, often from ingesting oil or losing their ability to regulate body temperature. For instance, the Deepwater Horizon spill resulted in significant bird mortality, with estimates suggesting up to 800,000 deaths.
Marine life can also suffer from lung and adrenal disorders linked to oil exposure, impacting fertility and overall health. Even fish larvae can develop heart defects due to contaminants. Furthermore, oil pollution harms essential components of the food web, such as phytoplankton and zooplankton, and can create dead zones where aquatic life cannot survive due to a lack of oxygen.
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How do oil spills harm sea animals and plants?
Oil spills cause significant harm to sea animals and plants. Birds, mammals, and sea turtles can become coated in oil, leading to death from ingesting it or from the substance interfering with their body temperature regulation. For instance, the Deepwater Horizon spill is estimated to have killed up to 800,000 birds.
Marine mammals like dolphins can suffer from lung and adrenal disorders linked to oil exposure, and fertility rates can be severely impacted. Fish larvae exposed to oil by-products may develop heart defects. Additionally, oil spills can create dead zones where oxygen is depleted, making survival impossible for aquatic life. Coral reproduction can also be hindered by oil and dispersants, and microorganisms vital to the marine food web can be killed.
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What methods are used to clean up oil spills?
Methods for cleaning up oil spills include the use of dispersants, which emulsify the oil, allowing bacteria to metabolize it more easily. Booms can be deployed to corral slicks, and the contained oil can then be siphoned off or burned. For shorelines, oil can be manually removed. Bioremediation, the treatment of pollutants using microorganisms like bacteria to break down undesirable substances, is also a method used for oil spills. In some cases, animals affected by oil spills are taken to rehabilitation centers for cleaning and medical evaluation before being released.
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What can people do to prevent oil spills in the future?
To prevent future oil spills, it is crucial to address the primary causes, which often stem from poor communication, inadequate worker training, lax enforcement of safety policies, improper equipment, and management that prioritizes rules over risk assessment. Implementing state-of-the-art digital management systems, known as digital oil fields (DOF), can significantly reduce human exposure to hazards by enabling remote monitoring and control of operations. Enhanced safety measures during production, including robust blowout preventers and continuous remote surveillance, are essential for early detection of issues. Furthermore, rigorous maintenance schedules for pipelines and transport vessels, along with strict adherence to local and international regulations, are vital steps in minimizing the risk of spills.
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oil spill, leakage of petroleum onto the surface of a large body of water. Oceanic oil spills became a major environmental problem in the 1960s, chiefly as a result of intensified petroleum exploration and production on continental shelves and the use of supertankers capable of transporting more than 500,000 metric tons of oil. Spectacular oil spills from wrecked or damaged supertankers are now rare because of stringent shipping and environmental regulations. Nevertheless, thousands of minor and several major oil spills related to well discharges and tanker operations are reported each year, with the total quantity of oil released annually into the world’s oceans exceeding one million metric tons. The unintentional or negligent release of used gasoline solvents and crankcase lubricants by industries and individuals greatly aggravates the overall environmental problem. Combined with natural seepage from the ocean floor, these sources add oil to the world’s waterways at the rate of 3.5 million to 6 million metric tons a year.
Oil-spill damage
The costs of oil spills are considerable in both economic and ecological terms. Oil on ocean surfaces is harmful to many forms of aquatic life because it prevents sufficient amounts of sunlight from penetrating the surface, and it also reduces the level of dissolved oxygen. Crude oil ruins the insulating and waterproofing properties of feathers and fur, and thus oil-coated birds and marine mammals may die from hypothermia. Moreover, ingested oil can be toxic to affected animals, and damage to their habitat and reproductive rate may slow the long-term recovery of animal populations from the short-term damage caused by the spill itself. Damage to plant life can be considerable as well; saltwater marshes and mangroves are two notable shore ecosystems that frequently suffer from oil spills. If beaches and populated shorelines are fouled, tourism and commerce may be severely affected, as may power plants and other utilities that either draw on or discharge into seawater at the shore. One of the industries most affected by oil spills is fishing. Major oil spills are frequently followed by the immediate suspension of commercial fishing, at the least to prevent damage to vessels and equipment but also to prevent the catch and sale of fish or shellfish that may be contaminated.
The immediate environmental effects of oil spills have been readily identified, but their long-term impact on the ecological system of an affected area is more difficult to assess. The cost of paying compensation to individuals and communities damaged by oil spills has been a major incentive to reduce the chances of such events taking place in the future.
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Oil-spill cleanup
As yet, no thoroughly satisfactory method has been developed for cleaning up major oil spills, though the spectacular spills of the last decades of the 20th century called forth great improvements in technology and in the management of coordinated responses. Essentially, responses to oil spills seek to contain the oil and remove enough of it so that economic activity can resume and the natural recovery processes of the marine environment can take over. Floating booms can be placed around the source of the spill or at entrances to channels and harbours to reduce the spreading of an oil slick over the sea surface. Skimming, a technique that, like the use of booms, is most effective in calm waters, involves various mechanisms that physically separate the oil from the water and place the oil into collection tanks. Another approach is to use various sorbents (e.g., straw, volcanic ash, and shavings of polyester-derived plastic) that absorb the oil from the water. Where appropriate, chemical surfactants and solvents may be spread over a slick in order to accelerate its natural dispersion into the sea. Onshore removal of oil that has penetrated sandy beaches and coated rocky shores is a laborious affair, frequently involving small armies of workers wielding hand tools or operating heavy construction-type equipment to scrape up contaminated debris and haul it away.
Largest oil-tanker spills in history
Two enormously important oil-tanker spills that took place in European waters were the Torrey Canyon disaster off Cornwall, England, in 1967 (119,000 metric tons of crude oil were spilled) and the Amoco Cadiz disaster off Brittany, France, in 1978 (223,000 metric tons of crude oil and ship fuel were spilled). Both events led to lasting changes in the regulation of shipping and in the organization of responses to ecological emergencies such as oil spills. In North America the Exxon Valdez oil spill of 1989 in Prince William Sound, Alaska, caused great ecological and economic damage, though it ranks well below the largest oil-tanker spills in history if measured by the amount of oil spilled (37,000 metric tons).
The largest oil-tanker spills in history are listed in the table.
| rank | ship name | year | location | spill size (metric tons) | damage |
|---|---|---|---|---|---|
| *Source of ranking and spill sizes: International Tanker Owners Pollution Federation. Sources of notes on damage: International Tanker Owners Pollution Federation; Centre of Documentation, Research and Experimentation on Accidental Water Pollution; and U.S. National Oceanic and Atmospheric Administration. | |||||
| 1 | Atlantic Empress | 1979 | off Tobago, West Indies | 287,000 | After a collision with another tanker, the Atlantic Empress caught fire and was towed 300 nautical miles out to sea, where it sank. Although its entire load of crude oil was lost, only minor ecological damage was reported on some island coastlines. |
| 2 | ABT Summer | 1991 | off Angola, southwestern Africa | 260,000 | Some 700 nautical miles off Angola, this tanker caught fire and sank with the loss of five crewmen. Its load of crude oil was lost, but no ecological damage was reported. |
| 3 | Castillo de Bellver | 1983 | off Saldanha Bay, South Africa | 252,000 | The Castillo de Bellver caught fire, broke in two, and sank. Its load of crude oil was dispersed by winds and currents. Only minor damage to wildlife and coastlines was reported. |
| 4 | Amoco Cadiz | 1978 | off Brittany, France | 223,000 | Suffering a failure of steering, the Amoco Cadiz grounded and broke in two. Its entire load of crude oil and ship fuel spilled, contaminating more than 300 km of Breton coastline and killing tens of thousands of birds and marine animals. Thousands of workers cleaned beaches and marshes in one of the largest oil-spill responses ever. |
| 5 | Haven | 1991 | Genoa, Italy | 144,000 | The Haven caught fire and broke apart. Some crude oil was recovered at sea, but some 100 km of coastline in Italy and France had to be cleaned mechanically. |
| 6 | Odyssey | 1988 | en route to Nova Scotia, Canada | 132,000 | Loaded with crude oil, the Odyssey broke in two and sank in the Atlantic Ocean 700 nautical miles from its destination. Because of the distance from land, no ecological damage was reported. |
| 7 | Torrey Canyon | 1967 | Isles of Scilly, off Cornwall, England | 119,000 | The Torrey Canyon ran aground and lost its entire load of crude oil, polluting coastlines in Cornwall as well as in the Channel Islands and in Brittany, France. Powerful solvents used in an attempt to disperse oil slicks were later determined to be more harmful to the environment than the spilled oil was. |
| 8 | Sea Star | 1972 | Gulf of Oman | 115,000 | The Sea Star, loaded with crude oil, collided with another tanker, burned, and sank with the loss of 12 crew members. No ecological damage was reported. |
| 9 | Irenes Serenade | 1980 | Bay of Navarino, Greece | 100,000 | This tanker caught fire while refueling at the port of Pylos and sank. Some spilled crude oil and ship fuel was salvaged on the sea surface, but some drifted ashore and had to be cleaned by hundreds of workers onshore and in small boats. |
| 10 | Urquiola | 1976 | La Coruña, Spain | 100,000 | Loaded with crude oil, the Urquiola ran aground in port and burned, with the loss of its captain. Some oil was salvaged from the vessel, recovered from the sea surface, or dispersed by a heavy application of chemicals, but much nearby coastline was coated with oil and debris and was only partly cleaned. |
| 11 | Hawaiian Patriot | 1977 | en route to Honolulu, Hawaii, U.S. | 95,000 | The Hawaiian Patriot cracked in a storm and then burned and sank 300 nautical miles from its destination, with the loss of a crew member. Ocean currents dissipated the spilled crude oil. |
| 12 | Independenţa | 1979 | near Istanbul, Turkey | 95,000 | The Independenţa struck another ship and burned at the southern end of the Bosporus, with the loss of 43 crew members. Most of the spilled crude oil burned, though some surrounding shorelines and beaches on the Sea of Marmara were fouled. |
| 13 | Jakob Maersk | 1975 | near Porto, Portugal | 88,000 | On entering the port of Leixões, the Jakob Maersk ran aground and burned, with the loss of seven crew members. Most of its spilled crude oil either burned or was contained and skimmed from the sea surface. Some drifted onto nearby beaches, which had to be cleaned mechanically and with dispersants. |
| 14 | Braer | 1993 | Shetland Islands, Scotland | 85,000 | Suffering engine failure in a storm, the Braer grounded at Sumburgh Head and broke up. High seas dispersed most of the spilled crude oil and ship fuel, but nearby salmon farms suffered large losses of stock. |
| 15 | Khark 5 | 1989 | off the Atlantic coast of Morocco | 80,000 | En route to the Netherlands, the Khark 5 caught fire briefly some 400 miles north of the Canary Islands and 120 nautical miles off the Atlantic coast of Morocco. One-quarter of its load of crude oil spilled; most of this was dispersed by wind and wave action, though some was reported to have reached beaches near Casablanca, where it was cleaned up manually. |
| 16 | Aegean Sea | 1992 | La Coruña, Spain | 74,000 | Entering port in rough weather, this tanker grounded, broke in two, and burned briefly. Most of its load of crude oil spilled. Wave and wind action dispersed part of the spill, but some 300 km of shoreline was polluted, and fishery in the area was temporarily suspended. |
| 17 | Sea Empress | 1996 | Milford Haven, Wales | 72,000 | On entering port, the Sea Empress grounded and spilled half its load of crude oil before being refloated. Much of the spill evaporated, was dispersed, or was recovered from the sea surface. An effective response was mounted to clean some 200 km of polluted shoreline. |
| 18 | Nova | 1985 | off Kharg Island, Gulf of Iran | 70,000 | |
| 19 | Katina P | 1992 | near Maputo, Mozambique, southeastern Africa | 66,700 | Damaged in a storm, the Katina P was grounded just offshore and spilled fuel oil from a hole in its hull. Most of the spill dispersed, but nearby mangroves were polluted, and shorelines were cleaned manually. |
| 20 | Prestige | 2002 | off Galicia, Spain | 63,000 | After suffering hull damage in severe weather, the Prestige was towed 130 nautical miles out to sea, where it sank. Much of the spilled load of heavy fuel oil was closely tracked and recovered at sea, and affected coastlines of northern Spain and western France were cleaned in well-coordinated responses. |