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small noaa logo Home | Emergency Response | Responding to Oil Spills
IntroductionWhyHowConstraints & ResultsImpactsWhere & Summary

Dispersants: A Guided Tour

People responding to an oil spill may use several kinds of "countermeasures" intended to reduce the harm caused by the spill. Dispersants are one kind of countermeasure. Here's a basic explanation of what they are and how they work.

an airplane applying dispersant to an oil slick

What are dispersants?

Once oil has spilled, people use oil spill countermeasures to try to reduce the adverse effects of spilled oil on the environment. Dispersants are one kind of countermeasure. They are chemicals that are applied directly to the spilled oil in order to remove it from the water surface, where oil can be especially harmful. In the photo above, an airplane is applying dispersant to an oil slick.

When dispersants are applied to surface oil slicks, they act to break up the slicks and move the oil, in the form of tiny droplets, from the water surface down into the water column (the volume of water extending from the surface to the bottom).

The diagram below shows how dispersants work:

  1. First, the dispersant is applied to the water surface.
  2. Next, molecules of the dispersant attach to the oil, causing it to break into droplets.
  3. Wave action and turbulence then disperse the oil-dispersant mixture into the water column, so that
  4. the oil that had been concentrated at the surface is diluted within the water column

Diagram of four panels showing oil floating on surface of water in beaker, dispersant added to oil, energy added by shaking beaker, and oil dispesant mixture results

IntroductionWhyHowConstraints & ResultsImpactsWhere & Summary
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