An oil spill is a 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. Oil spills include 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, and heavier fuels used by large ships such as bunker fuel, or the spill of any oily refuse or waste oil. Spills may take months or even years to clean up.

Oil also enters the marine environment from natural oil seeps. Most human-made oil pollution comes from land-based activity, but public attention and regulation has tended to focus most sharply on seagoing oil tankers.

The oil penetrates up the structure of the plumage of birds, 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 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 cause dehydration and metabolic imbalances.

Hormonal balance alteration including changes in luteinizing protein can also result in some birds exposed to petroleum. Most birds affected by an oil spill die unless there is human intervention. 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 bacterial. Sulfate Reducing Bacteria (SRB) and Acid Producing Bacteria are aerobic, 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.

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.

Recovering the oil is difficult and depends upon many factors, including the type of oil spilled, the temperature of the water (in warmer waters, some oil may evaporate), and the types of shorelines and beaches involved.

Methods for cleaning up include:

  Bioremediation: use of microorganisms or biological agents 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 soluble such as phenols and BTEX, forming gel-like agglomerations. Undetectable levels of hydrocarbons can be obtained in produced water and manageable water columns. By over spraying 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.

  Controlled burning can effectively reduce the amount of oil in water, if done properly.  But it can only be done in low wind, and can cause air pollution.

  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.

  Dredging: for oils dispersed with detergents and other oils denser than water.

  Skimming: Requires calm waters

  Solidifying.

  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, while the water is returned to the sea. Returning the water to the sea is the key, as otherwise the water, along with the oil, would need to be transported away from the spill - and the process becomes very inefficient. This method of using a centrifuge is, where allowed, an extremely efficient, and quick way to remove even the largest of oil spills. However, a regulation in the U.S., forcing any water returned to the sea to be 15 ppm or less in oil stops the whole process from being legal in the U.S. which applies to the current oil spill in the Gulf of Mexico. If is was happening off the coast of Holland instead - it would be getting quickly cleaned up, pretty much just as fast as the oil was gushing out of the well. As of June 27, 2010, the centrifuge machines developed by Costner and purchased by BP (32 of them on order, 20 delivered), are being deployed very slowly - to not at all, again due to this totally unneeded regulation.

Equipment used includes:

  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

  Seafood Sensory Training- in an effort to detect oil in seafood, inspectors and regulators are being trained to to sniff out seafood tainted by oil in the Gulf of Mexico and make sure the product reaching consumers is safe to eat.

  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.