ESS: Depletion of the ozone layer

Describe and evaluate the role of national and international organizations in reducing the emissions of ozone‑depleting substances. UNEP (United Nations Environment Programme) forges agreements on:

TIHC (International Trade in Harmful Chemicals) air pollution contamination of international waterways provide information to countries and public on disadvantages of pollution 1987 Montreal Protocol international agreement on the emission of ozone-depleting substances froze production and consumption of CFC's with goal of zero production by year 2000 LEDC's granted a longer time to implement the treaty China and India have not met their quotas under the MP because of their rapid economic growth and high demand for refrigeration & AC's good example of a successful international cooperative effort to alter human impact on the environment

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

1. Replace the old fridge with the existing "greenfreeze" technology which does not deplete the ozone 2. Recycle old CFC coolants from old fridges and air conditioners 3. Protection from excess UV e.g. sunglass and sun block

Explain the interaction between ozone and halogenated organic gases.

Halogenated organic gases(e.g. CFC) are very stable under normal conditions but can liberate halogen atoms when exposed to ultraviolet radiation in the stratosphere. These atoms react with monatomic oxygen and slow the rate of ozone re‑formation. Pollutants enhance the destruction of ozone, thereby disturbing the equilibrium of the ozone production system How ozone is depleted by CFC's: UV radiation breaks off a chlorine atom from a CFC molecule. The chlorine atom attacks an ozone molecule (O3), breaking it apart and destroying the ozone. The result is an ordinary oxygen molecule (O2) and a chlorine monoxide molecule (ClO). The chlorine monoxide molecule (ClO) is attacked by a free oxygen atom releasing the chlorine atom and forming an ordinary oxygen molecule (O2). The chlorine atom is now free to attack and destroy another ozone molecule (O3). One chlorine atom can repeat this destructive cycle thousands of times.

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

Increase in mutation rates in DNA causing cancer Can cause eye cataracts Can damage the ability to carry out photosynthesis in plants and phytoplankton Reduces primary production and therefore total productivity

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

Ultraviolet radiation is absorbed during the formation and destruction of ozone from oxygen.