Oil Spills
An oil spill can be defined as an accidental or deliberate dumping of oil or petroleum products into the ocean and its coastal waters, bays, and harbors, or onto land, or into rivers or lakes (Holum 1977). Between one and ten million metric tons (one metric ton is 1000 kilograms) of oil are put into the oceans every year. The oil is released, most often, in small yet consistent doses from tankers, industry, or on shore waste disposal (Boesh, Hersher, et al. 1974). Tanker spills cost the United States more than one hundred million dollars every year. Spill frequency increases proportionally with tonnage carried, in a linear manner. Non-tanker spills also increase linearly and account for thirty percent of all spills. The Atlantic area near Europe averages eight spills a year, the American area seven, and the Pacific two. Spills of more than ten thousand metric tons account for about two and a half percent of total spills, and spills above fifty thousand metric tons occur on average once a year. The average spill size is around seven thousand metric tons (Smets 1982). If left alone, oil spills will eventually break up naturally. The natural degradation is influenced by temperature, wind, wave action, the thickness of the oil, the degree of dispersion, and the oil 's tendency to form emulsions with water (Smith 1968). There are eight primary processes in the natural degradation of oil. The first step is spreading and motion. This step can be broken down into three smaller steps: gravity, viscous forces, and surface tension. Gravity initially spreads the oil into an even layer across the surface. Viscous forces then take over and account for even more spreading. The oil is finally spread into a monomolecular slick by the surface tension of the water. The second step of natural degradation is evaporation. The amount of evaporation that occurs is dependent on how far the oil slick has spread. There is a higher amount of evaporation when
References: Alvaro M, Fernandez S. 2001. Oiling of the Species. Times South Pacific 5 (2) :52-53. Beer T. 1983. Environmental Oceanography. New York: Pergamon Press. p. 161-165, 244, 249. Boesch D., Hershner C., Milgram J. 1974. Oil Spills and the Marine Environment. Cambridge, MA: Ballinger Publication Comp Boilema A, Cairns J. 1984. Restoration of Habitats Impacted By Oil Spills. Boston: Butterworth Publishers Dorfman A. 2001. A Sticky Situation. Time for Kids 6 (2) :4-5. Duffus J. 1980. Environmental Toxicology. New York: Halsted Press. p. Garrett W. 1975. The Tropospheric Transport of Pollutants and Other Substances to the Oceans. Washington DC: National Academy of Sciences. p. 169-180. Holum J. 1977. Topics and Terms in Environmental Problems. New York: John Wiley and Sons. p. 443-449 Smets H Smith J.E. 1968. Torrey Canyon Pollution and Marine Life. Cambridge, Great Britain: University Printing House. 191p.