Study Notes
Ozone depletion is caused by CFCs breaking down in the stratosphere, releasing chlorine atoms that destroy ozone molecules, leading to increased UV radiation reaching Earth. International efforts like the Montreal Protocol have significantly reduced CFC emissions, but challenges remain with replacement chemicals.
- Ozone Layer — a layer in the stratosphere containing high concentrations of ozone (O₃) that absorbs harmful UV radiation. Example: Protects life on Earth from UV-B and UV-C rays.
- Chlorofluorocarbons (CFCs) — man-made compounds used in aerosols, refrigerants, and solvents that are stable in the troposphere but break down in the stratosphere. Example: Release chlorine atoms that destroy ozone.
- Dobson Units (DU) — a measure of ozone concentration in the atmosphere. Example: A healthy ozone layer measures between 300–500 DU.
- Ozone Hole — a region where ozone concentration falls below 100 Dobson Units, notably over Antarctica. Example: Appears during Southern Hemisphere spring due to ideal conditions for ozone destruction.
- Montreal Protocol — an international agreement to phase out ozone-depleting substances. Example: Reduced CFC production by over 99% globally.
Exam Tips
Key Definitions to Remember
- Ozone Layer: A protective layer in the stratosphere that absorbs UV radiation.
- Chlorofluorocarbons (CFCs): Compounds that release chlorine in the stratosphere, leading to ozone depletion.
- Dobson Units (DU): A unit of measurement for ozone concentration.
Common Confusions
- Confusing the ozone hole with global warming.
- Believing that CFCs are still widely used today.
Typical Exam Questions
- What is the role of the ozone layer? It absorbs harmful UV radiation from the sun.
- How do CFCs contribute to ozone depletion? CFCs release chlorine atoms in the stratosphere that destroy ozone molecules.
- What is the significance of the Montreal Protocol? It is an international agreement that successfully reduced CFC emissions.
What Examiners Usually Test
- Understanding of how CFCs lead to ozone depletion.
- The impact of ozone depletion on human health and the environment.
- The effectiveness of international agreements like the Montreal Protocol.