19.ozone.depletion.10

19.ozone.depletion.10 - Refrigerators and Ozone Depletion...

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Unformatted text preview: Refrigerators and Ozone Depletion Structure of the Atmosphere Ozone in the Troposphere and Stratosphere Ozone Depletion Health/Environmental Effects Summary and Conclusions Sunlight and the Electromagnetic Spectrum Shorter wavelengths contain more energy UV. Ozone filters wavelengths below 290 nm. The Ozone Layer Absorbs Harmful UV Rays Filtering is protective for all life forms. Ozone in the Troposphere Undesirable Produced by electric motors and reactions between NOx and volatile organic chemicals. Sources of NOx include engines and other combustion. Sources of VOCs include engine exhaust and green plants. Ozone in the Stratosphere Desirable Ozone filters UV, converting it to less dangerous IR. Ozone Layer and the Atmosphere Normally temperature and pressure are directly related. Altitude is usually accompanied by a drop in pressure. However, ozone in the stratosphere reverses the trend. The Chlorofluorocarbons Refrigerants air conditioners and refrigerators. Spray propellants aerosol cans. Plastic foam blowing "styrofoam." Ozone-Depleting Chemicals Over Time Chain-Reaction Ozone Destruction by Nitric Oxide NO in the stratosphere can deplete ozone. Chain-Reaction Ozone Destruction by Freons Chlorine radical in the stratosphere can also deplete ozone. Ozone Depletion Most Severe at the Poles Arctic Ozone Averages Since 1979 Why the Poles? Chlorine radical is reactivated by ice crystals. Important Milestones in Ozone Depletion 1930 First production of CFCs by Frigidaire for refrigerators. 3 1974 Rowland (UCI) and Molina (UK) publish O hypothesis. 1978 EPA bans CFC use in spray-can propellants by 1979. 1985 UK researchers discover Antarctic ozone hole. 1987 Montreal Protocol targets 50% cut in CFC use by 1999. 1988 Dupont agrees with CFC role and ceases Reduced Ozone Causes Increased UV Exposure Reduced ozone permits increased UV reaching the earth's surface (of shorter wavelengths). UV is Highest at the Poles DNA Damage UV light has sufficient energy to break the bonds between DNA bases resulting in deleterious mutations. The Lower the Wavelength the Greater the Damag New H-Containing Freons are Better Why? They contain at least one H-atom in their structures. They are destroyed by hydroxyl radical in troposphere. Original Freons Discontinued in 1995 Use of the original freons was discontinued in 1995 in developed nations. However, they can still be acquired for repairs of older refrigerators and air conditioners. Conclusions The stratospheric ozone layer filters damaging UV radiation. Ozone depletion is most severe at the poles. Ozone is depleted by both freons and nitric oxide. Depletion is via a destructive chain-reaction process. Reduced ozone causes increased UV exposure. UV causes genetic damage and various other problems. ...
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19.ozone.depletion.10 - Refrigerators and Ozone Depletion...

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