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Ozone Depletion.docx

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Department
Life Sciences
Course
LIFESCI 2H03
Professor
Luc Bernier
Semester
Winter

Description
March 14 , 2013 Life Sci 2H03: Environmental Life Sciences Ozone Depletion Ozone Depletion - ozone layer is not as thick over Antarctica as a result of processes that lead to its destruction - the sun is a source of energy that drives the processes seen on Earth - energy reaches the Earth in form of radiation - X-ray, gamma rays are intercepted at high altitudes, carry the most energy - Visible light and ultraviolet radiation reach the Earth’s surface - UV contain a lot of energy and are intercepted by the ozone layer - Significant reduction in the amount of UV radiation reaching Earth’s surface due to being screened out by the ozone The Ozone Layer - troposphere: closet to the ground surface, where the weather processes are happening, storms, hurricanes, as altitude increases there is an increase in ozone - altitude peak concentration varies:  near the equator: 30km  polar regions: 15km - 90% of the ozone is in the stratosphere - ozone in the troposphere is associated with pollution - how do we measure concentration: based using balloon systems - measure thickness - can also be measured by satellites - DU: volume in which we are measuring the ozone, all the ozone over a certain area compressed down to 0 C and 1 atm pressure - Looking at column depth - Low ozone: lower DU, thick layer high DU - UVA:  Least energetic UV radiation  Not affected by stratospheric O 3  Not as problematic  Longest wavelength - UVB:  Most harmful form of UV radiation if it passes through ozone layer  This is the ozone problem - UVC:  Most energetic UV radiation  Strongly absorbed in the atmosphere Potential Impacts of UV Reaching Surface - UVC is strongly absorbed - UVA will lead to aging of the cells - UVB carries more energy and causes burning - UVC would lead to more problems yet we do not see them as they are absorbed by the ozone - Chapman mechanism: renewal of ozone Chapman Mechanism - O 2plits into 2O molecules Declining Ozone Levels - from 1980-mid1980 drop in ozone measured over Antarctica where the ozone layer is closest to the ground as temperature and pressure - sharp decline since the 1970s CFCs and the Ozone Layer: The L
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