1. Chapter 26 Ozone Depletion

2. Ozone A form of oxygen in which three atoms of oxygen occur together. Chemically active and has a short average lifetime in the atmosphere Forms a natural layer high in the atmosphere that protects us from harmful ultraviolet radiation from the sun A pollutant when present in the lower atmosphere

5. Ultraviolet Radiation and Ozone Ozone Shield: Stratospheric ozone layer that absorbs ultraviolet radiation Ultraviolet A: –Longest length, least energetic –Can cause some damage to living cells –Transmitted to earth Ultraviolet B: –Intermediate wavelength –Cause of Ozone Problem Ultraviolet C: –Shortest wavelength/ Most energetic

7. Measurement of Stratospheric Ozone Dobson Unit –Commonly used to measure the concentration of ozone

10. Ozone Depletion and CFCs Ozone depleted due to emission of CFCs CFCs are stable and have a long residence time in the atmosphere In stratosphere, release chlorine and enter into catalytic chain reaction- depletes ozone More UV radiation reaches lower atmosphere

15. Polar Stratospheric Clouds Clouds that form in the stratosphere during the polar winter Polar Vortex –Artic air masses that in the winter become isolated from the rest of the atmosphere and circulate about the pole –Rotates counterclockwise because of the rotation of the earth in the Southern Hemisphere

18. Management Issues Key issue is whether ozone depletion is natural or human-induced Montreal Protocol Collection and Reuse of CFCs Substitutes for CFCs –HFCs and HCFCs Evidence that replacements are also causing a problem