Assignment 5 - 1. Stratospheric Ozone a. Stratospheric...

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1. Stratospheric Ozone a. Stratospheric Ozone is important to humans because it prevents harmful UV radiation from reaching the surface of the earth. UVB and UVC radiation are very harmful to humans causing sunburn, skin cancer, genetic mutations and other disorders. The ozone absorption coefficient for the dangerous varieties of UV are very high so very few photons make it to the surface so unless we are exposed to the sun for a very long time we are basically safe from the bad UV. b. A catalyst is a substance that increases the rate of a chemical reaction but is itself unchanged by the reaction. An example of a catalytic cycle is the nitrogen catalytic cycle. In the nitrogen catalytic cycle NO acts as a catalyst. In the first reaction of the cycle nitric oxide reacts with ozone, forming nitrogen dioxide and molecular oxygen. In the second reaction of the cycle nitrogen dioxide reacts with atomic oxygen, reforming nitric oxide and producing a second O 2 molecule. So at the end of the cycle the NO is reformed, essentially unchanged by the reaction. c. The gradual depletion of ozone occurred due to the release of freons which were developed in the 1930s as blowing agents and refrigerants. As freons were released into the atmosphere they did not react in within the troposphere or the lower stratosphere. Once the freons reached the upper stratosphere they are photolyzed by short-wavelength UV radiation, which breaks the molecules apart and releases their chlorine as atomic Cl. The Cl then proceeds to destroy ozone through the chlorine catalytic cycle resulting in ozone depletion. d.
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This note was uploaded on 02/09/2009 for the course ATM S 10568 taught by Professor Lyattjaegle during the Fall '08 term at University of Washington.

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Assignment 5 - 1. Stratospheric Ozone a. Stratospheric...

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