IB ESS Topic 6.2: Stratospheric Ozone

Ozone - O3

a faintly blue-tinged odorless gas with the capacity to absorb ultraviolet radiation and convert it into heat energy.

- Dynamic equilibrium
- Balance between two ongoing processes
- UV radiation passing through the Earth's upper atmosphere is absorbed by the formation and destruction of ozone

Ultraviolet Radiation (UV)

- Damages human living tissues
- Increases the incidents of cataracts
- Mutation during cell division
- Skin cancer

UV radiation also affects other living organisms

- Damage to photosynthetic organisms
- Especially phytoplankton - basis of many aquatic food webs odel

Beneficial Effects of UV

- In animals stimulated the production of vitamin D
- Treats psoriasis and vitiligo (skin diseases)
- Steriliser, water purifier
- Forensics, lighting, lasers

Damage to the ozone

- CFCs
- HCFCs
- Halons
- Methyl bromide
- Nitrogen oxides (NO, NO2, N2O, NOx)

CFCs

- Usually very stable
- However, in the high stratosphere, the UV radiation breaks them down, releasing free chlorine atoms (very reactive)

Reducing ODS

Apply the 'replace, regulate & restore' model of pollution management

- Altering human activity producing pollution (replace)
- Regulate and reduce the pollutants at the point of emission
- Clean up & restoration

The Montreal Protocol 1987

UNEP (United Nations Environmental Programme):
- Key role in:
- Providing information
- Creating & evaluating international agreements
- Protection of stratospheric ozone

Montreal Protocol:
- International agreements on the reduction of ODS use
- National laws and regulations aimed at reducing consumption of ODS (CFCs in particular)

Why the Montreal Protocol is Important

- Best example of international cooperation on an environmental issue
- An example of the precautionary principle in science-based decision making
- Experts from many different fields coming together to research a problem and find solutions
- The first to recognise that different countries could phase-out ODS chemicals at different times depending on their economic status
- The first with regulations that were carefully monitored

Ozone-depleting Substances

Substances that cause the deterioration of the Earth's protection ozone layer.

Refrigerant

A substance used in a heat cycle usually including a reversible phase change from a liquid to gas.