Oil Spills

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Oil Spills

Introduction

Oil spills refer to the release of oil (liquid petroleum hydrocarbon) onto land or into water. The release can be accidental and due to human activity; the most well-known example is the loss of crude oil, a processed oil product such as gasoline or diesel fuel from a tanker following an accident near a seacoast or coast of a large freshwater river or lake.

More commonly, oil spills are the result of the leakage of oil or oily liquid from ships during their normal operation, and from runoff of oily wastes from the land into the water. Oil spills can also occur naturally and are the result of the seepage of oil from a seafloor deposit.

The environmental consequences of an oil spill can be devastating. Animals and birds are killed if they ingest the oil, and the oily coating on the fur or feathers can prove to be lethal. Also, the oily fouling of coastal beaches and vegetation can take months to remove, and can disrupt normal ecological functions for years.

Clean-up efforts have been aided by the use of microorganisms that have naturally adapted to use the hydrocarbons in an oil spill as a food source. As well, microbes can be genetically manipulated to be capable of digesting the pollutant, although the use of these genetically modified organisms in a natural environment is not usually done. However, if the oil spill can be collected and the fouled material transported to a secure site, use of the genetically modified bacteria can be useful.

Historical Background and Scientific Foundations

Oil spills caused by human error or accident have occurred ever since oil has been recovered from the ground and from the sea. Oil recovery is a complex process that involves drilling down into the ground or below the seabed to deposits, and—unless the oil formation is under great pressure that can push the oil to the surface—pumping the oil to the surface.

A century ago, oil production was more of a domestic issue, with seagoing transport of oil confined to small quantities carried aboard sailing ships. By the 1970s, however, with the demand for oil growing in countries including the United States, crude and processed oil was being loaded onto large tankers for transport all over the globe. The capacity of the tankers grew. In 2008, “supertankers” that stretch up to 1,770 ft (540 m) in length—almost the distance of six football fields—can hold up to two million barrels of oil.

From the time shipping began, it has been a hazardous practice. Storms, mechanical failure, and other calamities have caused countless shipping accidents. When this happens to an oil transport ship, the result can be an environmental disaster.

There have been hundreds of large ship-related oil spills since the beginning of the 1970s. The following are just a few noteworthy examples. In March 1972, the tanker Torrey Canyon ran aground off the coast of Cornwall in England and spilled nearly 120,000 tonnes of oil (one tonne is 1,000 kilograms or over 2,200 pounds). In 1976, the Argo Merchant ran aground off Nantucket in the United States, and spilled 25,000 tonnes of oil. The resulting film of oil on the surface of the water (an oil slick) was 100 mi (160 km) long and more than 50 mi (80 km) wide. Two years later, over 136,000 tonnes of crude oil were spilled onto more than 100 mi (160 km) of coastline near Portsall, France, when the tanker Amoco Cadiz ran aground.

In February 1983, a rupture at the Nowruz oil field in the Persian Gulf caused the release of 260,000 tonnes of oil. In August of the same year, the tanker Castillo de Bellver caught fire off the coast of South Africa, spilling

WORDS TO KNOW

BIOREMEDIATION: The use of living organisms to help repair damage such as that caused by oil spills.

ECOSYSTEM: The community of individuals and the physical components of the environment in a certain area.

GROUNDWATER: Fresh water that is present in an underground location.

POLLUTION: Physical, chemical or biological changes that adversely affect the environment.

252,000 tonnes of oil. In 1990, the tanker American Trader gashed its hull and the resulting oil spill off the coast of southern California created a 15-mi (24-km) long slick that contaminated the Boca Chica nature reserve. In the 1991 Persian Gulf War, a massive amount of oil was spilled from refinery terminals, anchored tankers, and oil wells during the Iraqi invasion of Kuwait. Estimates of the amount of oil that was spilled range up to 780,000 tonnes. In 1999, the Erika broke up in stormy seas off the Atlantic coast of France; the resulting slick polluted over 100 mi (160 km) of coastline. Finally in this brief list, a 2004 spill from the Terra Nova, an oil drilling platform in the Atlantic Ocean off the Canadian province of Newfoundland, killed up to 100,000 seabirds.

Oil spills can involve what is termed crude oil. The planet’s crude oil was made millions of years ago by the decay of plants and animals that settled onto seabeds. This decay formed deposits of crude oil, which today is recovered as a black liquid (oil that is contained in sandy formations in northern Alberta, Canada, is near molasseslike in consistency, and has to be recovered using very sophisticated and energy-intensive techniques). Crude oil is also known as petroleum. Tankers are one of the transportation routes used to transfer the crude oil to a facility called an oil refinery, where components including gasoline are separated in the process of refining and collected.

Both crude and refined oil are composed of molecules called hydrocarbons. These are sticklike molecules built of linked carbon atoms containing attached hydrogen molecules. This structure makes hydrocarbon virtually unable to dissolve in water; such compounds are termed “hydrophobic” (“water hating”). Because of its hydrophobic property, spilled oil will tend float on the surface of fresh and marine water, creating the oil slick.

As the slick is washed ashore by waves, the thick oil coats rocks, vegetation, sand, and living creatures that it contacts. The effects on wildlife can be disastrous. When oil coats a bird’s feathers, for example, it destroys the feather’s normal ability to repel water and retain air between the layer of feathers and the skin. As a result, the bird losses its ability to regulate its body temperature and dies of hypothermia, or drowns from the loss of buoyancy and the weight of the oil. Death can also result from poisoning, as the bird ingests oil in its attempt to clean itself. Birds that are poisoned but survive may have damage to organs including the liver, kidneys, and intestines, and may have difficulty in breeding. Females can become less capable of laying eggs.

Thus, an oil spill may not only affect bird populations immediately, but can disrupt population numbers for years afterward. Plants and animals can also be harmed or killed.

A frequent sight after an oil spill has fouled a coastline is the army of people attempting to clean up the spill. They may spray steam onto the spill, which can heat the oily coat and make it easier to wash off. As well, chemicals termed dispersants can be applied that cluster

IN CONTEXT: THE EXXON VALDEZ OIL SPILL, AN INFAMOUS AND LASTING LEGACY

Just after midnight on March 24, 1989, the fully loaded oil tanker Exxon Valdez, sailing from the port of Valdez, Alaska, and carrying just over 53 million gallons (200.6 million liters) of oil, hit the Bligh Reef in Prince William Sound, Alaska, at top speed. Nearly 11 million gallons (41.6 million liters) of oil were spilled into the Sound’s waters and fragile ecosystem.

Driven by winds and currents, the spill ultimately stretched 460 mi (740 km) and affected 1,300 mi (2,100 km) of shoreline. It is estimated that 250,000 seabirds, 2,800 sea otters, and 300 harbor seals were killed by the oil spill. In addition, 250 bald eagles and at least 22 Orca whales were killed. Billions of salmon and herring eggs were also destroyed.

Following the accident, the U.S. National Transportation Safety Board conducted an investigation into the causes. They found five events contributed to the grounding of the ship. First, the third mate, Gregory T. Cousins, did not maneuver the ship properly, probably because he was tired. Second, the ship’s captain, Joseph J. Hazelwood, did not provide an appropriate navigation watch. In his criminal trial, Hazelwood was found not guilty of operating a vessel while intoxicated, but guilty of negligent discharge of oil. Third, the Exxon Shipping Company was negligent in its supervision of Hazelwood and his crew. Fourth, the U.S. Coast Guard failed to adequately monitor the shipping traffic. Finally, the ship should have had a more effective pilot and escort service.

The event is considered one of the worst environmental disasters in U.S. history. It happened in an ecologically rich habitat, with rugged and inaccessible coastlines. Results from studies of the area affected by the oil spill showed that for at least twelve years, oil attributed to the spill could easily be found in the area. Surveys of beaches, for example, found significant amounts of oil below the surface in areas affected by the oil spills.

around the oil and form droplets that enclose the oil molecules. The dispersed oil needs to be collected before it washes back into the water. Other means of cleaning up spills include skimming the slick off the water’s surface and confining a slick inside a plastic ring known as a boom.

Clean up of an oil spill can be difficult, time consuming, and expensive. As an example, the 1989 spill from the Exxon Valdez tanker released enough oil to fill almost 125 Olympic-sized swimming pools. The slick, which fouled over 1,000 mi (1,600 km) of Alaskan coastline, took four summers to clean up. The clean-up involved 10,000 workers and 1,000 boats. Exxon’s bill for the clean-up was approximately $2.1 billion.

Impacts and Issues

The environmental consequences of oil spills cannot be understated. Environments and the wildlife in those environments can be affected for decades. For example, the Exxon Valdez spill fouled Alaska’s Prince William Sound, a productive fishery and area teeming with birds and wildlife. Studies conducted nearly 15 years later still demonstrated environmental damage. As of 2008, the region has essentially returned to the pre-spill state, but the damage lasted almost 20 years.

In the United States, the consequences of major oil spills that occurred in Pennsylvania in 1988 and the Exxon Valdez disaster spurred Congress to amend the Clean Water Act by passage of the Oil Pollution Act of 1990. This legislation improved the ability of the Environmental Protection Agency (EPA) and Coast Guard to response to spills and to prevent spills.

The response to the Exxon Valdez spill involved the use of bacteria that could use the oil hydrocarbons as food. This strategy had not been tried before, due to environmental concerns over the use of bacteria in a natural setting. The results, especially the application of a fertilizer spray to accelerate the bacterial breakdown of the hydrocarbons, were promising enough to spur the technology to become incorporated as a response option by the EPA, and spawned the new industry of bioremediation.

Remediation of oil spills has become an unfortunate legacy of the world’s dependence on fossil fuel. According to the EPA, even with more stringent shipping regulations and improved ship hull design, nearly 14,000 oil spills occur in freshwater and marine coastal waters every year.