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Ozone Depletion

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Chapter 26 Ozone Depletion Ozone The Basics A form of oxygen in which three atoms of oxygen occur together (O3) Chemically active and has a short average lifetime ... – PowerPoint PPT presentation

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Title: Ozone Depletion


1
Chapter 26
  • Ozone Depletion

2
OzoneThe Basics
  • A form of oxygen in which three atoms of oxygen
    occur together (O3)
  • 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
  • Rememberozone is a secondary pollutant.

3
Structure of Atmosphere Ozone Concentration
4
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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 because O3 absorbs it
  • Ultraviolet C
  • Shortest wavelength/ Most energetic

6
Part of the EMS showing UV radiation with
wavelengths between 0.01 and 0.4 um.
7
Measurement of Stratospheric Ozone
  • Dobson Unit
  • Commonly used to measure the concentration of
    ozone
  • 1 DU is to 1 ppb O3
  • Measurements of O3 began in 1970

8
Production of ozone in the Stratosphere.
9
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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 that depletes ozone
  • More UV radiation reaches lower atmosphere

11
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12
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

13
Hydrochlorid acid and chlorine nitrate are found
on the edges of polar stratospheric clouds
forming HCL ClONO2 ? Cl2 HNO3
14
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

15
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