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Chapter 26
Ozone Depletion
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 ultravioletradiation from the sun
• A pollutant when present in the loweratmosphere
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
Measurement of StratosphericOzone
• Dobson Unit– Commonly used to measure the concentration
of ozone
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
Polar Stratospheric Clouds
• Clouds that form in the stratosphere during thepolar winter
• Polar Vortex
– Artic air masses that in the winter become isolatedfrom the rest of the atmosphere and circulate about thepole
– Rotates counterclockwise because of the rotation of theearth in the Southern Hemisphere
Management Issues
• Key issue is whether ozone depletion isnatural or human-induced
• Montreal Protocol• Collection and Reuse of CFCs• Substitutes for CFCs
– HFCs and HCFCs• Short-Term Adaptation to Ozone Depletion