ozone

ozone formula

Ozone was formed when plants produced oxygen gas

O=O

Which was then split by uv-b radiation into 2 oxygen free radicals

O₂ →UV→ O^*+ O^*

And one of the free radicals joined up with another oxygen molecule

O₂ + O^* 🡪 O₃

UV then splits ozone into oxygen and an oxygen free radical again

O₃→UV→ O₂ + O^*

Both these reactions occur simultaneously in the ozone layer, so it can be written as one equation which is in dynamic equilibrium:

name and use of each Ozone Depleting Substances (ODSs)

Name	Use
CFC-11 & CFC-12	Plastic foam, refrigerant, aerosol propellant
Halons	Fire extinguishers
Carbon tetrachloride	Pesticides, synthetic rubber
Trichloroethane	Solvent for cleaning metals

ozone in the different parts of the atmosphere

in the troposphere - is highly toxic, and it is a dangerous pollutant

in the stratosphere it is critical to allow life to survive on Earth

Ozone Depletion –
Rowland-Molina Hypothesis

• UV splits up the CFC leaving a free radical Cl:

CCl₂F_{2 ^→} Cl^{* ₊ *}CClF₂

• This destroys ozone:

Cl^{* ₊} O₃ → ClO^{* ₊} O₂

• This destroys oxygen free radicals which means that new ozone cannot be formed from them:

  ClO^{* ₊} O^{* _→} Cl^{* ₊} O₂

Effects of ozone depletion

• human health - eye cataracts / mutations in DNA

• damage to plants - photosynthesis is less effective, and plants become susceptible to diseases

• damage to marine organisms.

Data Collection

• Ground based measurements 

• Aerial/Satellite Surveys 

Why ozone depletion has been greatest over Antarctica

• air is trapped due to polar vortex winds

• very low temperatures (-80)

• stratospheric clouds begin to form

• ice particles in the clouds catalyse ozone depletion as they have large surface areas

The restoration of the ozone layer

Main features of the Montreal Protocol (on Substances that Deplete the Ozone Layer) (1987):

• use of alternative processes

• use of alternative materials

• collection and disposal of CFCs and other ozone-depleting substances (ODSs).