The Ozone Layer….
Continuing on from our 101 on the atmosphere we now turn towards the Ozone layer, its composition, its effects upon the Earth and the reason why it’s so important. So what’s the deal here? Why is it so important? And how come 10 years ago everyone was banging on about it and now it’s all about climate change instead….
What actually is Ozone?
Oxygen normally exists as a diatomic gas in the form of O2 and it is the third most abundant element in the universe after hydrogen and helium. In certain states Oxygen can exist in the form of Ozone, which itself is a triatomic molecule consisting of 3 Oxygen molecules. Ozone or O3 is an allotrope of Oxygen. Its’ chemical composition of 3 Oxygen atoms ensures that O3 is a lot less stable than O2. At ground level O3 becomes an air pollutant and can cause serious distress to respiratory systems.
However, without O3 and the layer of Ozone within the stratosphere, the Earth would most likely be a radioactive wasteland. Ozone is formed naturally in the upper stratosphere by short wavelength ultraviolet radiation. Wavelengths less than ~240 nanometres are absorbed by oxygen molecules O2, which dissociate to give O atoms. The O atoms combine with other oxygen molecules to create ozone. In the stratosphere this reaction is almost continual and creates an almost perpetual Oxygen-Ozone cycle.
Within the stratosphere Ozone has a much longer half-life than it does on the surface. In the air and at low temperatures, Ozone can last for up to 3 months if unaffected by any other chemical reaction. The Ozone layer exists within the stratosphere at roughly 10-50km from the Earth’s surface and its main job is to filter out solar radiation. It is this layer that filters out over 94% of the Sun’s harmful UV rays. As photons pass through the atmosphere O2 is split and the UV rays are converted into thermal energy gently warming the stratosphere. Ozone is most effective at screening out UV-C and UV-B rays which possess the most potential for harming life on the planet.
Photolyze me baby....
So what’s all the fuss about?
Well as you can see the Ozone layer and its production process is essential for human, animal and vegetable existence (minerals will probably survive just like cockroaches). Without the Ozone layer the Earth would be bombarded by solar radiation. Throughout 1910’s – 1950’s a meteorologist called Dobson began setting up world wide apparatus for the measurement of O3. In the early 70’s, scientist began to investigate a perceived reduction in the amount of O3 within the atmosphere. And in 1985 a team of British scientists discovered that there was a considerable hole in the Ozone layer above the Antarctic region. The word ‘hole’ is perhaps an over exaggeration as there was still a thin, yet highly reduced, layer of Ozone above the South Pole. With a depleted O3 layer more UV-B and UV-C entered through the atmosphere hitting the Antarctic region. I assume that this is what gave rise to the much debated global warming theory along with other global temperature and CO2 statistics (thou I haven’t fully researched into that bit yet).
After the discovery of the Ozone layer, and the rampant publicity, people finally began to take notice about the potentially dangerous consequences of Ozone depletion. A series of studies throughout the 70’s and 80’s discovered that CFC’s were responsible for the majority of Ozone depletion across the globe. CFC’s are able to penetrate into the atmosphere where they are then split into free radicals via UV light. These free radicals are then capable to catalyse in the atmosphere creating a chain reaction with the ability to breakdown over 100,000 Ozone molecules. CFCs also unfortunately have a half-life of around about 50 years. In 1987 after the Montreal Protocol the production of CFCs was limited and CFCs were eventually phased out by 1996.
Fortunately latest reports indicate that Ozone depletion has slowed in recent years thanks to the international ban on CFCs. Due to the long half-lives of CFCs, and the residual amounts of CFCs still in existence in older appliances such as car radiators and fridges; Ozone depletion is still occurring. It may take a lifetime for the Ozone hole to be fully repaired, but thanks to international action we have at least identified, and apparently halted, one potential factor that can effect worldwide climate change.
3 Comments to “The Ozone Layer….”
Good post! I plan to move into this stuff after I’m done with school, as most of it is time consuming. It’s a great post to reference back to. My blog needs more time to gain in popularity anyway.
This is great! Now I want to see your ways for us readers to become more involved! Expect an email later today.
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