To understand atmospheric ozone, it is important to know how it is formed. In a previous post, I pointed out how ground-level ozone affects humans differently than the higher-up stratospheric ozone (thus the quip, “Good on high, bad nearby”1.) The way they are formed is different as well. Stratospheric ozone is formed when solar ultraviolet radiation strikes ordinary oxygen molecules (O2) and disassociates them into single atoms of oxygen. The ultraviolet energy is absorbed by the oxygen and does not reach the ground. These single atoms are extremely reactive and combine with nearby oxygen molecules to form triatomic oxygen or ozone (O3)2.
The ultraviolet radiation that forms ozone also destroys it when the radiation strikes an ozone molecule and breaks it up into an ordinary oxygen molecule and a free atom of oxygen. Thus ozone in the stratosphere is constantly being created and destroyed so that it does not accumulate past a certain amount3. In my next post, I’ll discuss how ground-level ozone is formed.
- For example, see the Almanac of Policy Issues. To view, click here.
- NASA Earth Observatory, Chemistry in the Sunlight: The Chemistry of Ozone Formation To view, click here. You can see an excellent YouTube video of the process by clicking here.
- NASA Earth Observatory, Chemistry in the Sunlight: The Chemistry of Ozone Formation To view, click here.