What Is Ozone And How Is It Formed?
A gaseous layer (O3 ) in the upper atmosphere that protects the earth from harmful ultraviolet radiation from the sun. At lower levels, ozone becomes a major pollutant.
"The ozone layer" refers to the ozone within stratosphere, where over 90% of the earth’s ozone resides. Ozone is an irritating, corrosive, colorless gas with a smell something like burning electrical wiring. In fact, ozone is easily produced by any high-voltage electrical arc (spark plugs, Van de Graaff generators, Tesla coils, arc welders). Each molecule of ozone has three oxygen atoms and is produced when oxygen molecules (O2) are broken up by energetic electrons or high energy radiation.
Troposphere – Stratosphere
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. Supersonic jet airliners such as Concorde fly in the lower stratosphere whereas subsonic commercial airliners are usually in the troposphere. The narrow region between these two parts of the atmosphere is called the "Tropopause".
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) – typically ~260 DU near the tropics and higher elsewhere, though there are large seasonal fluctuations. It is created when ultraviolet radiation (sunlight) strikes the stratosphere, dissociating (or "splitting") oxygen molecules (O2) to atomic oxygen (O). The atomic oxygen quickly combines with further oxygen molecules to form ozone:
When and Where was the first ozone hole detected ?
Dramatic loss of ozone in the lower stratosphere over Antarctica was first noticed in the 1970s by a research group from the British Antarctic Survey (BAS) who were monitoring the atmosphere above Antarctica from a research station much like the picture to the right.
What Is The Ozone Hole?
A popular name given to a phenomenon discovered in 1987, when scientists measured unexpectedly low ozone concentrations in the stratosphere above the South Pole during the Antarctic spring.
Over Antarctica (and recently over the Arctic), stratospheric ozone has been depleted over the last 15 years at certain times of the year. This is mainly due to the release of manmade chemicals containing chlorine such as CFC’s (ChloroFluoroCarbons), but also compounds containing bromine, other related halogen compounds and also nitrogen oxides (NOx). CFC’s are a common industrial product, used in refrigeration systems, air conditioners, aerosols, solvents and in the production of some types of packaging. Nitrogen oxides are a by-product of combustion processes, eg aircraft emissions.