Ozone depletion
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Ozone Depletion. Ozone. O 3 is an unstable molecule formed when O 2 is split by UV making 2 O atoms which then recombine with O 2 in atm to reform O 3 Ozone layer = high concentration of ozone in the lower stratosphere with maximum concentration at ~25 km altitude

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Ozone Depletion

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Ozone depletion

Ozone Depletion


Ozone

Ozone

  • O3 is an unstable molecule

    • formed when O2 is split by UV making 2 O atoms which then recombine with O2 in atm to reform O3

  • Ozone layer = high concentration of ozone in the lower stratosphere

    • with maximum concentration at ~25 km altitude

    • 12 ppm concentrations effectively block incoming damaging ultraviolet radiation

      • naturally shields life from

        UV’s harmful effects


The ozone hole

Not really hole; more of a thinning

Defined as concentrations of <200 ppb (<200 DU)

1 ppb of O3 = 1 Dobson unit (DU)

Ozone “hole” over Antarctica each spring (Sept.-Nov.)

Thinning since 1980s

levels over Antarctica had declined by 40-60%

Depletion also in Arctic & globally

Lets in more UV radiation

The Ozone “Hole”


Ozone depletion1

Ozone Depletion

  • Ozone layer in stratosphere damaged by Ozone Depleting Chemicals (ODCs)

    • Halons

      • fire extinguishers

    • Carbon tetrachloride

      • solvent

    • Methyl chloroform

      • cleaning solvent & propellant

    • ***CFCs (cholorfluorocarbons)


Ozone depletion

CFCs

  • cheap to produce

  • very stable, nonflammable, & noncorrosive

    • lasting up to 200 years in the atmosphere

  • Freons, used in aerosol sprays, ACs, & solvents

    • 1 million metric tons/year were produced

  • Releases chlorine atoms that split ozone

    • A single chlorine atom removes about 100,000 O3 molecules before it is taken out of operation by other substances

  • In 1988 CFCs were no longer manufactured.

    • Nevertheless, by 1988 some 320,000 metric tons of CFCs were used worldwide.

  • Many countries have recently passed laws banning nonessential use of these chemicals.


How to protect the ozone

How to Protect the Ozone

  • Stop producing ODCs

    • Substitutes are available for almost all CFCs

      • Hydrocholorfluorocarbons (HCFCs)

      • Hydrofluorocarbons (HFCs)

      • Helium

      • Hydrocarbons (HCs)


What s being done to reduce o 3 depletion

What’s Being Done to Reduce O3 Depletion?

  • 1987 Montreal Protocol on Substances that Deplete the Ozone Layer

    • Landmark international agreement

      • Effective January 1, 1989

        • Five revisions

          • 1990 (London), 1992 (Copenhagen), 1995 (Vienna), 1997 (Montreal), 1999 (Beijing)

    • Meeting of 36 nations to cut emissions of CFC’s

      • Aimed to reduce emissions by 35% from 1989-2000 eventually eliminate all ODCs by 2006

        • Based on success of treaty ozone levels expected to return to normal around 2050

      • Also halons, carbon tetrachloride, & methyl chloroform


The montreal protocol is a success

The Montreal Protocol is a Success

  • Today, production & use of ODCs has ↓ 95%

    • The ozone layer is beginning to recover

  • Considered biggest enviro. success story

    • Policymakers included industry in helping to solve the problem

    • Implementation of the plan allowed an adaptive management strategy that changed strategies in response to new scientific data, technological advances, & economic figures

  • The Montreal Protocol can serve as a model for international environmental cooperation


Clean air act

Clean Air Act

  • Motor Vehicle Air Conditioning

    • CFC’s have been used as a coolant in motor vehicles

    • Scientists wanted to make sure existing CFC is used efficiently and not wasted

    • This Act lists provisions for new machines to make sure they meet standards for emissions

  • Product Labeling

    • Establishing label requirements for products manufactured with Class I ODCs

    • Labeling of Class II substances required by 2015

    • Made to make public aware of Ozone depletion due to use


Challenges still face us

Challenges Still Face Us

  • CFCs will remain in the stratosphere for a long time

  • Nations can ask for exemptions to the ban


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