Naked Science Forum
Life Sciences => The Environment => Topic started by: 4getmenot on 03/08/2006 05:16:22
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They say that there is a hole in the ozone layer about three times the size of texas. If there is then why does our oxygen stay in? How come it is not released thru the hole and such all the oxygen out???
k
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Firstly, ozone is oxygen.
Oxygen is an atom with 8 protons and (depending upon its isotope) usually about 8 neutrons.
Oxygen is a very very reactive atom, and is very rarely found very long on its own.
Most of the oxygen in our atmosphere is actually composed of molecules of two oxygen atoms bound together (what is known a diatomic oxygen). This is more stable than a lone oxygen atom on its own. In ozone, you have three oxygen atoms bound together. This is slightly less stable than diatomic oxygen, but in certain situations will be produced. There are even situations where ozone is produced at low levels in the atmosphere, such as by lightning, in car engines, even by the humble photocopier and laser printer. Ozone is actually harmful for humans and other animals, although will be tolerated in small quantities. Ozone is also harmful to bacteria, and is sometimes used instead of chlorine as an anti-bacterial agent (its advantage and disadvantage over chlorine is that it will fairly quickly break down to the more stable, and less harmful, diatomic oxygen).
At very high altitudes, where the atmosphere is exposed to far more radiation from the Sun and elsewhere that never actually reaches ground level, a significant amount of the diatomic oxygen that exists lower in the atmosphere is converted to the triatomic form, the form we know of as ozone. This ozone is useful because it is better at blocking more of the ultraviolet light from reaching us at ground level, and most life at ground level is not used to large quantities of ultraviolet light, and it can be harmful to many organisms (including promoting skin cancer in humans). Because this ozone exists in large quantities at high levels, it does not matter that the ozone itself is harmful to breath in, because we would not be breathing in any of it.
Since ozone quickly breaks down to diatomic oxygen, it only exists at high altitudes insofar as the speed of breakdown is balanced by the speed at which it is created. It is believed that certain chemicals that we produce might accelerate the speed at which ozone degenerates to the diatomic form of oxygen. Observations have shown that over large parts of Antarctica (and to a lesser extent over the Arctic), the rate at which ozone is converted back to diatomic oxygen is faster than the rate at which the solar radiation can create new ozone from the available diatomic oxygen. The images that show where the ozone is show a hole in the middle of the image. This does not mean that the oxygen in the ozone has gone away, it simply means that the the form the oxygen takes is different. The reason why this has effected Antarctica particularly badly is because of the cold temperatures, but even more because of the particular nature of the air circulation over Antarctica.
George
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The atmosphere isn't held down by some sort of special layer, it is held down the same way you are - gravity. so even if there were no ozone the oxygen would still be here (unless the UV getting in killed all the plants and algae of course)
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Originally posted by daveshorts
(unless the UV getting in killed all the plants and algae of course)
It certainly is not going to be doing that. It may disadvantage certain species, but we have seen around Chernobyl just how quickly life can adapt to harsh environments, and I imagine that the environment around Chernobyl is far harsher than than that which will ensue simply by the removal of the ozone shield.
George
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Actually I doubt it if you think on pure energy terms the Chernobyl radiation is probably of the order of a couple of MW spread over thousands of square km. UV on the other hand outside the atmosphere is probably getting on for a 50W per square meter so 50MW per square km, and as the radiation is spread out over thousands of square km you would have to compare it to tens of gigawatts of UV. Not a problem to anything fairly thick, but the surfaces of plants and animals, which we are talking about, could suffer a lot of damage.
Ok it probably wouldn't kill off photosynthesis, but would cause a lot of problems to more complex plants and animals.
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quote:
Originally posted by daveshorts
Actually I doubt it if you think on pure energy terms the Chernobyl radiation is probably of the order of a couple of MW spread over thousands of square km. UV on the other hand outside the atmosphere is probably getting on for a 50W per square meter so 50MW per square km, and as the radiation is spread out over thousands of square km you would have to compare it to tens of gigawatts of UV. Not a problem to anything fairly thick, but the surfaces of plants and animals, which we are talking about, could suffer a lot of damage.
Ok it probably wouldn't kill off photosynthesis, but would cause a lot of problems to more complex plants and animals.
Power aside, as you mention, UV is only absorbed externally, while radioactive contamination is also consumed internally.
But comparisons aside, I have no doubt that within a few generations, there would return a resilient range of complex life that has well adapted to the extra UV radiation. There would be a shock effect, and it may mean that there will be a shift in the balance of species (the more so because some species will be exposed to the higher UV earlier, and develop tolerance earlier, and will thus be in a position to take advantage of the shock effect on neighbouring areas as the local species there had not yet adapted to the extra UV).
George