The Ozone Layer

The Ozone Layer

1. The Ozone layer is in a layer called the Statosphere

   • Ozone molecules are called O3
     • The Ozone Layer is constantly being replaced
   • Ozone is formed when UV Radiation from the Sun hits oxygen molecules
   • If the right amount of UV Radiation is absorbed by an oxygen molecule, the oxygen molecule splits into separate atoms or free radicals
     • The free radicals then combine with other oxygen molecules to form Ozone moleciules
       • O + O --> O2 + O --> O3
     • O + hv --> O + O
       • Where hv is a quantum of UV Radiation
     • UV Radiation can also reverse the formation of Ozone
       • O3 + hv --> O2 + O

2. The Ozone Layer protects the Earth

   • The UV Radiation from the Sun is made up of different frequencies
     • These frequencies are grouped into 3 band
       • UVA UVB UVC
         • UVC has the highest frequency and the most energy
         • UVB can damage the DNA in cells and cause skin cancer
       • We need UV radiation to make Vitamin D
     • The Ozone layer removes all the high energy UVC Radiation and about 90% of UVB
       • These types of UV Radiation are harmful to humans and most other life on Earth

3. The Ozone Layer is Breaking Down

   • In the 1970s and the 1980s, scientists discovered that the ozone layer about Antarctica was getting thinner
     • These holes in the Ozone layer are bad because the allow more harmful UVB Radiation to reach the Earth
       • CFCs absorb UV Radiation and split to form chlorine free radicals
         • These free radicals destroy ozone molecules and are then regenerated to destroy more ozone
           • One Chlorine atom can destroy 10,000 ozone molecules before it can form a stable compound
         • CFCs are non toxic, non-flammable and chemically inert
       • NO free radicals from nitrogen oxides destroy ozone too
         • Nitrogen oxides are produced by car and aircraft engines AND thunderstorms
       • The reactions can be represented by these equations, where R represents either Cl or NO
         • R + O3 --> RO + O2
           • RO + O --> R + O2
             • Formed when UV breaks down O2
         • The overall reaction is O3 + O --> 2O2

4. What is Being done to Slow down the Depletion of the Ozone Layer?

   • The Montreal Protocol
     • The Montreal Protocol sets out guildlines for developed and developing countries for all the major ozone depleting substances, including CFCs, halons and less damaging transitional chemicals such as HCFCs.
       • The Montreal Protocol targets 96 chemicals in thousands of applications across more than 240 industrial sectors.
         • Other Ways to Reduced Greenhouse Gas Emmision
           • Governments are successfully using a wide range of policies and measures to address climate change, including regulations and standards, taxes and charges, tradable permits, voluntary agreements, subsidies, financial incentives, research and development programs
     • The Protocol has been further admended - London 1990, Copenhagen 1992, Vienna 1995, Montreal 1997 and Beijing 1999
       • Which have brought forward phase out schedules and added new ozone depleting substances to the list of substances controlled under the Montreal Protocol.
         • CFCs have then been banned
           • They were found in:
             • Hairspray
             • Coolants for Pridges
             • Air Conditioning Systems
         • Since the Montreal Protocol came into effect, the atmospheric concentrations of the most important chlorofluorocarbons and related chlorinated hydrocarbons have either leveled off or decreased
           • Halon concentrations have continued to increase, as the halons presently stored in fire extinguishers are released, but their rate of increase has slowed and their abundances are expected to begin to decline by about 2020.
             • The Montreal Protocol has often been called the most successful international environmental agreement to date
         • Halon concentrations have continued to increase, as the halons presently stored in fire extinguishers are released, but their rate of increase has slowed and their abundances are expected to begin to decline by about 2020.

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