botkin and keller environmental science 5e chapter 25 ozone depletion

Botkin and KellerEnvironmental Science 5e

Chapter 25

Ozone Depletion

Botkin and KellerEnvironmental Science 5e

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

Botkin and KellerEnvironmental Science 5e

Botkin and KellerEnvironmental Science 5e

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

Botkin and KellerEnvironmental Science 5e

Botkin and KellerEnvironmental Science 5e

Measurement of Stratospheric Ozone

• Dobson Unit– Commonly used to measure the concentration

of ozone

Botkin and KellerEnvironmental Science 5e

Botkin and KellerEnvironmental Science 5e

Botkin and KellerEnvironmental Science 5e

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

Botkin and KellerEnvironmental Science 5e

Botkin and KellerEnvironmental Science 5e

Botkin and KellerEnvironmental Science 5e

Botkin and KellerEnvironmental Science 5e

Botkin and KellerEnvironmental Science 5e

Botkin and KellerEnvironmental Science 5e

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

Botkin and KellerEnvironmental Science 5e

Botkin and KellerEnvironmental Science 5e

Botkin and KellerEnvironmental Science 5e

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

• Short-Term Adaptation to Ozone Depletion