POLLUTION MANAGEMENT

5.6 Depletion of stratospheric ozone

Assessment Statements 5.6.1 Outline the overall structure and

composition of the atmosphere. 5.6.2 Describe the role of ozone in the

absorption of ultraviolet radiation. 5.6.3 Explain the interaction between

ozone and halogenated organic gases. 5.6.4 State the effects of ultraviolet

radiation on living tissues and biological productivity.

Assessment Statements 5.6.5 Describe three methods of

reducing the manufacture and release of ozone-depleting substances.

5.6.6 Describe and evaluate the role of national and international organizations in reducing emissions of ozone-depleting substances.

5.6.1 Outline the overall structure and composition of the atmosphere.

Air is made up of 78.1 % Nitrogen, 20.9 % Oxygen, 0.93 % Argon, and 0.038 % Carbon Dioxide. It also has trace amounts of helium ozone, hydrogen and methane.

These gases are found in significant concentrations at the following altitudes:

Ozone 10-50 km Nitrogen 100-200 km Oxygen 200-1100 km Helium 1100-3500 km Hydrogen Above 3500

km

5.6.2 Describe the role of ozone in the absorption of ultraviolet radiation.

Ozone is essential for sustaining life. The highest concentration occurs in the upper part of the atmosphere, the stratosphere.

Short-wave UV radiation breaks down oxygen molecules into two single oxygen atoms. The free oxygen combines with oxygen molecules to form ozone.

The UV radiation is converted into thermal energy heating the stratosphere, and thereby shields the earth from harmful radiation that would otherwise destroy most life on the planet.

5.6.3 Explain the interaction between ozone and halogenated organic gases.

Halogen is a group of 5 non-metal elements with similar chemical bonding: Fluorine, Chlorine, Bromine, Iodine, and Astatine.

They react with metals to form salts.

Halogenated means a halogen atom has been added.

When halogenated gases are hit with UV radiation, they break down and release the halogen atom.

The halogen atoms then act as catalysts for reactions that destroy ozone molecules.

5.6.4 State the effects of ultraviolet radiation on living tissues and biological productivity.

UV-B is the most harmful, which causes eye damage and cataracts, sunburn and skin cancers.

Short term exposure can lead to snow-blindness.

Chronic skin exposure can cause wrinkling, thinning, and loss of elasticity.

It can also lead to decreased immune responses to infectious agents, and may reduce the effectiveness of vaccines.

Crops that are sensitive can have reduced yields.

5.6.5 Describe three methods of reducing the manufacture and release of ozone-depleting substances.

CFCs from aerosol cans, gas-blown plastics, and refrigeration will likely get replaced with HFCs, ammonia, carbon dioxide, and hydrocarbons.

Nitrogen oxide can be reduced by using less fossil fuels, less polluting engines, and cleaner plane engines.

Trigger sprays for Aerosols, collecting leaking CFCs, incinerating CFC waste, and recycling old refrigerators.

Replacing currently polluting devices with more efficient one.

5.6.5 Describe three methods of reducing the manufacture and release of ozone-depleting substances.

Methyl Bromide is an odorless, colorless gas used as a soil fumigant to control pests across a wide range of agricultural sectors which depletes stratospheric ozone layer.

USA and Europe phased it out in 2005, now is only used for eliminating quarantine pests and in places that have no technical or economical alternatives.

5.6.6 Describe and evaluate the role of national and international organizations in reducing emissions of ozone-depleting substances.

National and international organizations have had large effects on the use of ozone depleting substances.

In 1985 UNEP implemented the Vienna Convention for the Protection of the Ozone Layer, which looked at protecting human health and the environment.

In 1987 the Montreal Protocol on Substances that Deplete the Ozone Layer, which has reduced the use of ODS by 99% in MEDCs and by 50% in LEDCs.