chapter18

S replace incandescent light bulbs with fluorescent

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Unformatted text preview: ess of protective ozone layer in stratosphere process most effective at low temperatures and in presence of sunlight ozone holes therefore near poles; seasonal changes ozone destruction most severe in early spring decline first noticed in 1980s ozone hole caused by human action alone; no natural process known to destroy ozone layer 27
 o o o o o o o o o chlorofluorocarbons (CFCs) attack and destroy ozone molecules in stratosphere sunlight breaks down CFCs; Cl recombines with one of the oxygen atoms of O3 CFCs have very long lifetime so can destroy ozone over a long time it has been conjectured that the ozone hole will likely increase before the ozone layer recovers, despite recent efforts to reduce CFC input Montreal Protocol established in 1987: CFC phased out by 1996 by 140 countries, incl. U.S. unlike Kyoto, Montreal was ratified by many because the (sole) human cause of CFC production was more obvious effects from CFC reduction not expected to be effective before 2025 in 2006, the Antarctic ozone hole was the largest ever another problem: other halocarbons - like hydrochloro-flourocarbons (HCFC) replaced CFCs. These are less destructive to the ozone layer but are nevertheless greenhouse gases. These will be phased out by 2030. HFCs (hydroflourocarbons) are also greenhouse gases but their lifetime in the atmosphere is significantly shorter than CFCs and HCFCs. NB: the ozone hole does not contribute to global warming/global warming and the ozone hole are two phenomena that are not related. Ozone absorbs in the infrared (IR) part of the spectrum, but much more so in the ultraviolet (UV) part. The ozone hole lets more UV light to Earth's surface which does not directly warm the planet. Figure 18.x A house in Los Angeles tented for termite fumigation. (source: Wikipedia) Until 2000, an often used fumigant to eradicate termites from homes was methyl bromide (or bromomethane, CH3Br). Like nearly every other fumigant used in this business, it is toxic and cumbersome preparations include the removal of all foods, toiletry and clothing as well as plants and animals from the homes. Methyl bromide depletes the ozone layer and so was phase out after the Montreal Protocol. It has since been replaced in termite control by sulfuryl fluoride (SO2F2). The problem with this agent, however, is that it is a ...
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This document was uploaded on 11/21/2013.

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