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OZONE!

OZONE!. “Good up high, Bad nearby”. Stratospheric. Tropospheric. Interesting characteristics of O 3. Highly poisonous, strong odor, irritant, colorless gas (We’ll study health effects in the spring .) Chemically much more active than O 2 Beneficial uses: Purify water

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OZONE!

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  1. OZONE! “Good up high, Bad nearby”

  2. Stratospheric Tropospheric

  3. Interesting characteristics of O3 • Highly poisonous, strong odor, irritant, colorless gas (We’ll study health effects in the spring.) • Chemically much more active than O2 • Beneficial uses: • Purify water • Sterilize air • Bleaching certain foods (flour)

  4. Reminder about stratospheric formation O2 + UV light  2O 2O + 2O2  2O3

  5. Why we care • Ozone layer blocks 95-99% of the incoming UV light • UV light disrupts, destroys complex molecules (life)  human health (mainly cataracts and cancer), animal health, lots of crop damage • What’s causing the damage to the layer?

  6. Amazing CFC’s • Easily liquified! • Relatively inert! • Non-toxic! • Non-combustible! • Refrigerants, propellants, used in making styrofoam, industrial solvents (also “halons” which can contain bromine for fire retardants) • Because of their inertness, diffuse slowly, unchanged into stratosphere

  7. Troposphere: • Thinnest layer, 80% mass, almost all H2O • .04 ppm O3 • Stratosphere: 10 ppm O3

  8. Why is ozone thinning seasonal? During sunless winter, polar stratospheric clouds (PSC’s) form within vortex This special cloud surface is ideal for “chlorine reserve compounds” (CFC’s, HCl, ClONO2)

  9. Main Reactions CF2Cl2 + UV light  cleaves Cl Cl + O3  ClO + O2 ClO + O  Cl + O2 What is the “role” Cl is playing in these reactions?

  10. Cl acts as “catalyst” not reactant • Catalyst - alters the rate of a reaction, essentially “unchanged”, and so can react over and over again. • One molecule of chlorine can potentially degrade over 100,000 molecules of ozone before it is removed from the stratosphere or becomes part of an inactive compound!

  11. Timeline • Mid-70’s recognized problem • Manufacturer’s resistance (CFC’s useful!) • 1987 Montreal Protocol banned product internationally (phased out) • But CFC’s are stable, insoluble in H2O, so may be 2070 before ozone completely restored IF no additional threats are introduced.

  12. http://www.theozonehole.com/2012ozonehole.htm

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