How ozone is formed and how it affects our atmosphere
Ozone is a nearly colorless gas which consists of three atoms of oxygen.1 According to the Material Safety Data Sheet for ozone, it is an unstable gas which, at normal temperatures, decomposes into a single oxygen atom (O) and biatomic oxygen (O2). The agent mainly responsible for the production of ozone is solar ultraviolet radiation, which dissociates oxygen molecules into atoms; the free oxygen atoms then combine with other oxygen molecules to form ozone.
The following chemical equations show how ozone is formed and destroyed:
1. O2 + hv => 2O, [for a solar radiation wavelength (hv) less than 240 nm]
2. O + O2 => O3
3. O3 + hv => O2 + O, [for solar radiation wavelength (hv) less than 325 nm]
4. O + O3 => 2O2 [This reaction, resulting in ozone loss, is relatively slow. If it were the only mechanism for ozone loss the stratospheric ozone layer would be about twice as thick as it is!2]
Where, O = an oxygen atom; h = Planck's constant (6.626075 x 10-32 J s); v = frequency (s-1); hv = E (energy of a quantum, in Joules); nm = nanometer.
Creation of an ozone molecule
Ultraviolet solar radiation drives the process of ozone creation and depletion
Ozone occurs naturally in the atomosphere and about 90% of it is concentrated in a layer at a height of from 10 to 40 kilometers above mean sea level.3 This atmospheric layer is known as the stratosphere. According to physical chemist Dr. Robert Parson, at the University of Colorado, the concentration of stratospheric O2 always far exceeds the concentration of O3.4 "Thus, ozone absorbs UV radiation without itself being consumed; the net result is to convert UV light into heat. Indeed, this is what causes the temperature of the stratosphere to increase with altitude, giving rise to the inversion layer that traps molecules in the troposphere." As Dr. Parson goes on to write, "The ozone layer isn't just in the stratosphere; the ozone layer is responsible for the existence of the stratosphere." For more information on the stratosphere and other layers in the atmosphere, click here.
More information regarding stratospheric ozone can be found at this NOAA webpage.