UNIT 2.1 Ozone: What and Where is it?
THE DISCOVERY OF OZONE
In 1785, the Dutch chemist Martinus van Marum noticed an unusual smell when he was conducting experiments involving electrical sparking above water. He attributed it to the electrical reactions, failing to realize that he had in fact created ozone. Half a century later, Christian Friedrich Schönbein noticed the same pungent odour and recognised it as the smell that often followed a bolt of lightning. In 1839, he succeeded in isolating the gaseous chemical and named it “ozone”, from the Greek word ozein (ὄζειν) meaning “to smell.”
Ozone is also known as trioxygen. It is an inorganic molecule with the chemical formula O3. Ozone in its gaseous state ranges from colorless to pale blue. It has a pungent smell which resembles that of chlorine. This smell is easily detected even in very low concentrations (as low as 100 ppb in air).1
WHERE OZONE IS FOUND
Ozone is found in the earth’s atmosphere. The highest level of ozone is found in the stratosphere, which is also known as the ozone layer. The stratosphere spans about 10km and lies 50km above the earth’s surface. Low levels of ozone are also found in the troposphere, which is the closest atmospheric layer to the earth’s surface.2
The structure and the properties of ozone will be looked into in the next section.
WHY IS IT IMPORTANT?
Ozone is a gas in the stratosphere which acts as a barrier to protect living things on earth from harmful ultraviolet radiation (UV). It does this by absorbing the UV rays from solar radiation, only allowing very small amounts of UV to reach the earth’s surface that remain harmless to living things.
Without the ozone layer, high concentrations of ozone will reach the earth’s surface, stunting the growth of plants as well as killing off phytoplankton that serve as staple food for most aquatic organisms. Thus, the food chain will be heavily impacted. There are others consequences which will be discussed in the later sections.3
Figure 1: This picture shows how the ozone layer acts a good protective zone by reflecting harmful UV rays from the sun.
References:
1 http://www.lenntech.com/library/ozone/history/ozone-history.htm
2 http://www.ozonelayer.noaa.gov/science/basics.htm
3 http://earth.rice.edu/mtpe/atmo/atmosphere/topics/ozone/o3.html
Figure 1: http://envis.tropmet.res.in/kidscorner/ozone.htm