The management of oil spills may require the use of a variety of controls, including booms, skimmers, and dispersing agents. The key to effectively combating an oil spill and preventing damage to the shoreline and the environment is the careful selection and use of the appropriate equipment. The conditions of the spill site, as well as the type of oil, are important. The conditions at sea, the water currents, and the wind also can have a profound effect upon spill control efforts.
How Oil Dispersants Work
When used correctly, dispersants can be an effective response to an oil spill. They may be able to rapidly remove large amounts of certain types of oil from the sea's surface. Through their action, dispersants help separate oil particles and prevent clumping, thus ultimately allowing these particles to more easily enter into the sea water. Then, micro-organisms that occur naturally in the marine environment can start the biodegrading process. These organisms can also delay the formation of persistent water-in-oil emulsions.
Heavier crude oil does not disperse as well as light to medium weight oils. Dispersants are most effective when applied immediately after a spill before the lightest materials in the oil have evaporated.
Environmental Factors that Affect Dispersants
- Salinity of water - most work best at a salinity level close to that of the ocean.
- Temperature of water - dispersants work best in warmer water.
- Conditions at sea - wave action must be strong enough to break up the oil slick.
Use by Foreign Countries
Some countries rely almost exclusively upon dispersing agents to control oil spills because rough, choppy conditions at sea make mechanical containment and cleanup quite difficult. Experts have found that wave energy will cause an oil slick to break up into small oil droplets that are rapidly diluted and then, subsequently, biodegraded by the marine microorganisms.
Use in the United States
Dispersants can not be used in freshwater according to EPA policy unless authorized by an On-Scene Coordinator, who sees its use as necessary to protect human health. They have not been used extensively in this country's waters because of possible long term environmental effects, difficulties with timely and effective application, on-going disagreements between scientists who are researching their effectiveness, the long term effects on the environment and issues of toxicity.
In the Exxon Valdez Oil Spill in Alaska, attempts were made to use a dispersant to clean up but were discontinued because there was not enough wave action to mix the dispersant with the oil in the water.
Dispersants should not be used on gasoline or diesel spills.
The Future of Dispersants
New technologies that improve the application of dispersants are being designed and their effectiveness is being tested in laboratories and on actual spills. The dispersants used today are less toxic than those used in the past; however, their long term effects on the environment are still unknown.
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