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Ozone (O3) in the Atmosphere

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Ozone (O3) in the Atmosphere The good, the bad, the mesospheric? In the Troposphere ( Bad Ozone ) Harmful pollutant Created in a reaction between nitrogen oxides ... – PowerPoint PPT presentation

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Title: Ozone (O3) in the Atmosphere


1
Ozone (O3) in the Atmosphere
  • The good, the bad, the mesospheric?

2
In the Troposphere (Bad Ozone)
  • Harmful pollutant
  • Created in a reaction betweennitrogen oxides
    (NOx), volatile organic compounds (VOCs) and
    sunlight
  • Highest concentrations in warm summer weather
  • Created in urban areas, blown hundreds of miles
    by the wind

Image Source cfpub.EPA.gov
3
Sources of NOx and VOCs?Human Pollution!
5 Other
5 Consumer Solvents
17 Fuel Combustion
45 Motor Vehicles
56 Motor Vehicles
22Utilities
50 Industrial/CommercialProcesses
Sources of NOx
Sources of VOCs
Image Source www.EPA.gov
4
Why should we care?
  • Breathing ozone can reduce lung function and
    create scar tissue in the lungs
  • Ozone damages vegetation
  • Harms ecosystems
  • Reduces agricultural yields

Image Source www.arcweb.archives.gov
5
In the Stratosphere (Good Ozone)
  • 99 of ozone is found here
  • Ozone layer is produced naturally
  • O2 UV radiation ? 2 OO O2 M ? O3 M
  • (M is inert, usually O2 or N2)
  • Also destroyed naturally
  • O3 UV radiation ? O O2
  • O O3 ? 2 O2

6
In the Stratosphere (Good Ozone)
  • Through these reactions, Ozone absorbs harmful
    radiation from sun (UVC and some UVB rays)
  • This protects plants and crops from
    damage,protects UV-sensitive marine life,
    andprotects humans from skin cancer
  • Also warms the stratosphere

7
What about the ozone hole?
  • In the Stratosphere
  • Human use of aerosol sprays and air conditioners
    has changed chemistry of the atmosphere
  • Chlorofluorocarbons (CFCs) contain chlorine (Cl)
    and bromine (Br)

Image Source ozonewatch.gsfc.nasa.gov
8
Cl destroys O3 in Stratosphere
  • CFCl3 UV radiation ? CFCl2 Cl
  • Chlorine is now free to react with O3

Image Source ozonewatch.gsfc.nasa.gov
9
Cl is a serial killer
  • Cl O3 ? ClO O2
  • ClO O3 ? Cl 2 O2
  • Ozone is destroyed, but Cl is unchanged
  • It lives to kill again!

Image Source ozonewatch.gsfc.nasa.gov
10
Why is the hole over Antarctica?
  • Very cold winters and surrounding oceans combine
    to create polar vortex of extremely cold air
  • Polar Stratospheric Clouds form
  • Droplets in clouds provide sites for chemical
    reactions that set the stage for ozone
    destruction when the sun comes out in the spring

Image Source ozonewatch.gsfc.nasa.gov
11
Is the O3 hole still a problem?
  • Global community agreed to phase out O3 depleting
    chemicals in 1987 (Montreal Protocol)
  • CFCs are long-lived in atmosphere O3 layer not
    expected to recover before 2050

Image Source ozonewatch.gsfc.nasa.gov
12
Ozone in the Mesosphere
  • 1 of atmospheric ozone is found here
  • Ozone is created each night and then destroyed
    each day
  • Seasonal variations?
  • Protects Stratospheric ozone layer?

13
Ozone in the MesosphereDiurnal Variations
  • O3 is created at night
  • O O2 M ? O3 M
  • (M is inert, usually O2 or N2)
  • And destroyed during the day
  • O O3 ? 2 O2
  • O3 H ? OH O2
  • O3 UV ? O O2

daylight
MOSAIC data
14
Ozone in the MesosphereSeasonal Variations
  • Water vapor and sunlight destroy O3
  • H2O UV radiation ? H OH
  • O3 H ? OH O2
  • More water vapor in mesosphere during winter and
    summer?

Summer
MOSAIC data
Winter
15
No Ozone in the Thermosphere
  • O atoms are too far apart to combine into O3
    molecules
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