Review Questions

1. What is a Dobson unit? How is it used in relation to atmospheric ozone levels?

2. If the overhead ozone concentration at a point above the Earth's surface is 250 DU, what is the equivalent thickness in millimeters of pure ozone at 1.0 atm pressure?

3. Describe the process by which chlorine becomes activated in the Antarctic ozone-hole phenomenon.

4. What are the steps in Mechanism II by which atomic chlorine destroys ozone in the spring over Antarctica?

5. Explain why full-scale ozone holes have not yet been observed over the Arctic.

6. What are two effects on human health that scientists believe will result from ozone depletion?

7. Define what is meant by a tropospheric sink.

8. Explain what HCFCs are, and state what sort of reaction provides a tropospheric sink for them. Is their destruction in the troposphere 100% complete? Why are HCFCs not considered to be suitable long-term replacements for CFCs?

9. What types of chemicals are proposed as long-term replacements for CFCs?

10. Chemically, what are halons? What was their main use?

11. What gases are being phased out according to the Montreal Protocol agreements?

Coping with Asthma

Coping with Asthma

If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.

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