Ozone (O3: 3 oxygen atoms) occurs naturally in the atmosphere.
The earth's atmosphere is composed of several layers. We live in the "Troposphere" where most of the weather occurs, such as rain, snow and clouds. Above the troposphere is the "Stratosphere"; an important region in which effects such as the Ozone Hole and Global Warming originate.
Ozone forms a layer in the stratosphere, thinnest in the tropics (around the equator) and denser towards the poles.
The amount of ozone above a point on the earth's surface is measured in Dobson units (DU). Around 260 DU near the tropics and higher elsewhere, though there are large seasonal fluctuations.
Ozone is created when ultraviolet radiation (sunlight) strikes the stratosphere, splitting oxygen molecules (O2) to atomic oxygen (O). The atomic oxygen quickly combines with further oxygen molecules to form ozone:
|
O2 + Ultraviolet radiation |
-> |
O + O |
|
|
O + O2 |
-> |
O3 |
|
It's ironic that at ground level, ozone is a health hazard. However, in the stratosphere we could not survive without it. For it absorbs some of the potentially harmful ultra-violet (UV) radiation from the sun that can cause skin cancer and damage vegetation, among other things.
© 2005 Al Bawaba (www.albawaba.com)
