1. Our Natural Protection Against UV light. The Ozone layer that blocks out the sun’s harmful rays is being depleted. Todd Olsen Professor Kimball Chem 1A 31193

2. What is causing the Depletion of the Earth’s natural defense from the sun? Man-made compounds are responsible for the destruction. The most common are chlorofluorocarbons (CFC’s) and halons. The halogens Chlorine, Bromine, and Fluorine are often found in these compounds. And when broken down to their elemental state are the cause of the depletion. We will get to this later. Man-made compounds are responsible for the destruction. The most common are chlorofluorocarbons (CFC’s) and halons. The halogens Chlorine, Bromine, and Fluorine are often found in these compounds. And when broken down to their elemental state are the cause of the depletion. We will get to this later. Chlorofluorocarbons are used for various purposes by man: Chlorofluorocarbons are used for various purposes by man:

3. What Is Ozone Ozone is a gas that forms from 3 oxygen atoms (O3). It exists in 2 places in our atmosphere. The ground level near the earth known as the troposphere. This O3 is responsible for smog in large cities and causes harmful effects to us as well as plants and animals. Ozone exists above the Stratosphere and this O3 protects us and the planet from the sun’s ultraviolet rays (UV-b).

4. Uses of CFC’s

6. These items that give comfort and ease to our everyday lives contain these ozone damaging compounds which allow them to operate. When CFC’s are released into the air after use they travel through the atmosphere until they reach the stratosphere where the sun breaks down the molecules to their elemental state. It’s in this state that the halogens, particularly Cl and Br can damage the Ozone layer. These items that give comfort and ease to our everyday lives contain these ozone damaging compounds which allow them to operate. When CFC’s are released into the air after use they travel through the atmosphere until they reach the stratosphere where the sun breaks down the molecules to their elemental state. It’s in this state that the halogens, particularly Cl and Br can damage the Ozone layer. These can take years to reach this level of the atmosphere. 1 molecule of Cl or Bromine can destroy many thousands of molecules. They do so by reacting with O3 by catalytic cycles. Or to make it more simple. A number of reactions can occur. These can take years to reach this level of the atmosphere. 1 molecule of Cl or Bromine can destroy many thousands of molecules. They do so by reacting with O3 by catalytic cycles. Or to make it more simple. A number of reactions can occur.

7. A simple reaction that Damages O3 (Ozone) Cl + O3 --- ClO + O2. In this simple reaction Cl reacts and bonds with one of the oxygen atoms in O3 leaving behind just a normal Oxygen O2 molecule.

8. This original Cl atom isn’t done! Suppose this ClO atom that we have from the last reaction is still floating around above the stratosphere. It meets up with a lone O atom and forms a new reaction. Suppose this ClO atom that we have from the last reaction is still floating around above the stratosphere. It meets up with a lone O atom and forms a new reaction. ClO + O --- Cl + O2. ClO + O --- Cl + O2. Cl is back to it’s original state and is now free to break down another O3 molecule. Cl is back to it’s original state and is now free to break down another O3 molecule.

9. How Long will this Cl atom last on this repeating cycle? Through these simple reactions, a simple Cl or Br atom can destroy thousands of O3 molecules like we just looked at. It can continue until it gets back down to the troposphere. Through these simple reactions, a simple Cl or Br atom can destroy thousands of O3 molecules like we just looked at. It can continue until it gets back down to the troposphere. Here that same Cl atom from earlier can bond with an H atom to form HCl and finally remove it from it’s destructive cycle. Here that same Cl atom from earlier can bond with an H atom to form HCl and finally remove it from it’s destructive cycle. However it can take years for this to make the transition from Stratosphere to troposphere. And while it’s falling it’s doing it’s damage. However it can take years for this to make the transition from Stratosphere to troposphere. And while it’s falling it’s doing it’s damage.

10. Why Care? Well… Well…

12. Gross? Isn’t it! That was a picture of a victim of skin cancer. Increased exposure of UV-b rays can lead to more causes of skin cancer, cataracts, and impaired immune system. That was a picture of a victim of skin cancer. Increased exposure of UV-b rays can lead to more causes of skin cancer, cataracts, and impaired immune system.

13. Not just damaging to us. More UV-b rays also will damage these: More UV-b rays also will damage these:

14. Simple Soybean plants Soybean plants are very sensitive to UV-b light and will cause them to yield much less of a crop. Soybean plants are very sensitive to UV-b light and will cause them to yield much less of a crop.

15. Fish Too. Phytoplankton is a tiny plant that is instrumental in the marine food chain. Many parts of the world rely on fishing as a main source of food. If you damage the beginning of the food chain, there won’t be as many fish in the end of the links. Phytoplankton is a tiny plant that is instrumental in the marine food chain. Many parts of the world rely on fishing as a main source of food. If you damage the beginning of the food chain, there won’t be as many fish in the end of the links.

16. What is being done and what we can do. The Environmental Protection Agency (EPA) has a long term plan to reduce and eventually phase out these chemicals containing CFC’s that cause the Ozone to decay. Regulations have been established which require labels on Ozone depleting substances and the EPA is also prohibiting non-essential Ozone depleting products.

17. What about You? Only use maintenance people that are EPA certified (referring to recovery of refrigerant, or Freon) to work on your vehicles, refrigerators, and air conditioners. Only use maintenance people that are EPA certified (referring to recovery of refrigerant, or Freon) to work on your vehicles, refrigerators, and air conditioners. Check these items regularly for leaks. Check these items regularly for leaks. Repair leaks before refilling them with more refrigerants. Repair leaks before refilling them with more refrigerants. Dispose of this equipment to local agents that are EPA certified. Dispose of this equipment to local agents that are EPA certified.

18. The Ozone will heal itself. But that is a long and slow process. Not in any of our lifetimes in fact! All we can do is not advance the damage further. It will eventually recover.