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Реферат: Oil Degrading Microbes Bioremediation Essay Research Paper

Название: Oil Degrading Microbes Bioremediation Essay Research Paper
Раздел: Топики по английскому языку
Тип: реферат Добавлен 14:45:14 01 ноября 2010 Похожие работы
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Oil Degrading Microbes: Bioremediation Essay, Research Paper

During recent years, the public has become increasingly aware of the hazards of oil spills. Photographs and vivid descriptions of oil-soaked birds floundering on oil covered shores have become routine coverage by the news and media.Oil spillage has become an increasing problem with the advent of offshore drilling and the transport of petroleum in large tankers. The extent and effects of oil pollution are of great concern to the world today. A recent study estimated that the amount of oil spilled into the ocean is between five to ten million tons annually. The major sources include: cargo tanker washings at sea, waste oil pumping at sea, in-port oil losses, tanker accidents, exploration losses and, motor oil. The Fate of Spilled Oil According to a well-known axiom that water and oil don t mix, it might be expected that spilled oil would float around until it was washed ashore. However, his is not the case. A single gallon of oil can spread enough to cover up to four acres of water. As soon as oil is spilled in a marine environment, changes begin to occur. Within days 25% of the oil spilled is lost through evaporation. The remaining oil goes through an emulsification process that leads to the formation of a very thick and heavy material, which sinks to the bottom of the ocean. This material adheres to almost all objects it encounters. Microorganisms and photo-oxidation degrade oil that survives the emulsification process. After three months, 15% of the original oil volume remains. This is in the form of dense black lumps, which end up on shores. If a substantial oil spill took place close to shore, rather than at sea, the effects would be different because there wouldn t be sufficient time for the process described above to affect the total amount of oil involved. Thus, a sticky film of oil would cover any solid surface that came in contact with the oil. Short and Long Term Effects of Oil Pollution Short-term effects receive the most publicity because they are immediately obvious. The long-term effects become apparent after much research.Short-term effects of oil spills include:(1) Reduction of light transmission, which hampers marine plants and protist growth by reducing the rate of photosynthesis.(2) Reduction in dissolved oxygen.(3) Damage to marine birds. Swimming and diving birds covered with oil can drown or become handicapped. Eventually, oil soaked birds will die as a result of exposure in cold water or their inability to get food.(4) Toxic effects to marine environment. Crude oil is a complex mixture, made up of various compounds. Certain crude oils are toxic to marine life and humans. Such compounds include: benzene, toluene, xylene, naphtalene and phenanthrene. Within days of an oil spill, a massive destruction of aquatic life can occur. The species affected include a wide range of fish, shellfish, worms, crabs, microcrustaceous and other invertebrates.

Long-term effects of oil spills: Chemical messengers in seawater mediate many important biological processes that are important to the survival of the organism. For example, many marine organisms rely on chemical messengers for processes such as finding food. The oil compounds interfere with such processes by blocking the taste receptors of organisms or by mimicking the natural stimuli which cause disastrous effects on the survival of some marine organisms. Certain crude oil fractions are quite chemically stable, and once incorporated into a particular organism, they can pass through the food chain and even reach marine organisms that are harvested for human consumption. Recent reports have shown that the oil can serve as a concentration medium for poisons such as pesticides that can reach marine organisms and humans in concentrations much higher than otherwise.Countermeasures for oil spills: Since the principal cause of oil spills is human error, efforts should be directed towards prevention of oil spills. However, some accidents will still take place in spite of any prevention method. Then what do we do?Presently, mechanical methods to clean up oil spills include the following:(1) The use of skimmers to remove oil from the surface of the water. (2) The use of booms or barriers to contain the oil slick which is to be skimmed off the surface. (3) The use of chemical dispersants, detergents and solvents.(4) Burning of the oil has been attempted but it does not undergo complete combustion and unburned black smoke contains toxic components. BioremediationPerhaps the best, most environmentally safe prospect for the clean up of oil spills is the use of oil hungry microorganisms. Bioremediation is a microbial clean up approach that can be used to degrade petroleum products as well as a number of hazardous pollutants. This biological technique involves the seeding and fertilization of an oil spill with a high concentration of microorganisms called petrophiles which biologically degrade oil and convert it into masses of food and non-toxic living cells. This cell mass is assimilated up through the aquatic food chain. Within days of treatment, changes to the oil composition and appearance can be observed. The treated oil slick begins to break up and turn into a yellowish substance that eventually diminishes in size. This substance consists of some remaining smaller sized oil fractions intermixed with the microbial mass that will eventually be consumed by higher forms of marine life.

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