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 spills have significant long-term effects. These effects can be broken down into the long-term recovery of an ecosystem, chronic pollution, and persistent contamination of ecosystems. In the recovery of an ecosystem, organisms that have been depopulated, have to reproduce. This is a slow process. At times, when a dominant species has been removed, others can gain an advantage through atypical survival of their young, and rearrange the order of the ecosystem. Marine communities have a more rapid rate of succession than land communities such as forests, but it still takes several years. The amount of time needed for total recovery depends on the structural complexity of the system and the degree of damage that was done. Persistent contamination or chronic pollution severely hinders and slows an ecosystem's ability to recover. Chronic pollution occurs when an environment is exposed to the persistent, continuous release of petroleum from refineries, petrochemical plants, oil ports, and other waste discharges. Burning is biologically innocuous. Wicking agents or oxidants often need to be used so that the oil will burn better. This is only feasible on small, contained oil slicks. Chemical dispersal is more of a cosmetic treatment than an overall clean up, because more often than not, it injects oil more solidly into the ecosystem rather than removing it. Chemical dispersal should only be used in extreme cases such as fire hazards and the restoration of important amenities. Steam cleaning exterminates intertidal life and does more harm than good. The general consensus is that physical removal and absorbents are the most reliable non-destructive methods (Boesch, Hershner, et al 1974). The next step is direct sea to air exchange. Wave-produced spray transfers hydrocarbons to the air in the same way salt is transferred (Beer 1983). There is a constant cycle of hydrocarbons between the sea and the air, but these are more localized along tanker routes, and coastal areas (Garrett 1975). Emulsification is the fourth step in the natural degradation process. Insoluble components of the oil emulsify with the ocean water and are described as oil in water or water in oil emulsions, depending on the ratio of one to another (Beer 1983). Emulsions can contain up to eighty percent water. As the mass of the oil in the emulsions decreases through evaporation, the specific gravity or density increases, which makes the emulsions more likely to sink (Smith 1968). Using absorbents is the favored method in North America. Straw is applied to soak up the oil. There is a slight ecological impact because the dried straw and oil deposits are more persistent than oil alone in intertidal areas. Peat moss and synthetic absorbents such as oleophilic plastic polymers are also used, but they increase the problem of the persistence of non-biodegradable absorbent material. Bird death tolls from oil spills are recorded for the animals that reach the shore. It is believed that this accounts for roughly five to fifteen percent of the actual bird mortalities from oil spills. Diving sea birds have inordinate mortalities from oil spills. Other birds, such as seagulls and shearwaters, appear to avoid oil slicks on the water. One reason for the difference in mortality may be that when the diving birds resurface, they come up under an oil slick. The primary effect of oil on birds is the fouling of feathers, which disrupts insulation and buoyancy. This causes them to sink, drown, or lose body heat. Birds can also inges
Some common words found in the essay are:
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