Dispersants are chemicals that are applied directly to an oil slick. The key components of chemical dispersants are surface active agents called surfactants (also known as detergents). Chemical dispersants assist with breaking up the slick into small droplets ranging in size from a few micrometers to a few millimeters.
Chemical dispersants can do this because they contain molecules that are both water compatible and oil compatible. The molecules align themselves around the oil droplets as the droplets break away from the slick. This action prevents the coalescence (reforming or joining) of oil droplets so the oil can no longer form a slick on the water surface, and it reduces the adherence of the oil to solid particles (sand) and hard surfaces (seawalls and boat hulls).
Chemical dispersants remove the oil from the surface of the water and into the water column. Once in the water column, the oil is diluted to less harmful levels, and eventually is used as a food by bacteria. Birds, marine mammals, turtles and Florida's sensitive coast are protected when oil is removed from the water surface. Chemical dispersants do not cause the oil to sink but remain in suspension in the water column.
Not any chemical dispersant may be used. Only chemical dispersants that are listed on the National Product Schedule (NCP) may be used to treat oil spills. Manufacturers who want to list their chemical dispersants on the NCP must complete specific tests demonstrating effectiveness of at least 45 percent, aquatic toxicity, and identify ingredients. The results of these tests are sent to the U.S. Environmental Protection Agency for evaluation.
Are chemical dispersants toxic? Yes, but the dispersants used today are generally not as toxic as the oil itself and, with adequate dilution, will not harm aquatic life. As an added precaution, chemical dispersants are not applied to shallow nearshore waters, mangrove areas, marshes, or waters over coral reefs and seagrass beds.
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Florida Department of Environmental Protection Office of Emergency Response 850-245-2010
September 24, 2019 - 11:22am
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The Florida Department of Environmental Protection is the state’s lead agency for environmental management and stewardship – protecting our air, water and land. The vision of the Florida Department of Environmental Protection is to create strong community partnerships, safeguard Florida’s natural resources and enhance its ecosystems.