Реферат: The Ozone Layer Essay Research Paper The
The Ozone Layer Essay, Research Paper
The Ozone Layer
The ozone layer is one of the most important source of protection that exists on Earth. It is a region of the stratosphere containing a high concentration of ozone, and it prevents a great amount of ultraviolet and other high-energy radiation from penetrating to the earth s surface.
The ozone layer has been a security blanket that lies on top of the earth, protecting it from harmful rays, however, humans have abused of the use of CFCs, and other industrial chemicals that are now destroying this layer and causing big worries and health risks to all living things.
There have been many holes discovered on the layer, and scientist are deep into research to find new ways to solve this problem. What follows, will discuss the structure of the ozone layer, so that it can be understood what is happening when it is being destroyed. Also, different pollutants and how they can be avoided will be researched in order to come up with a unique solution to this dangerous problem.
The Ozone Layer
The ozone layer is one of the oldest things on the planet, older than any of the ancient creatures we see in our museums today. The ozone layer has provided protection for the living components under it for millions of years, and without the ozone layer, we most likely would not be here today. The ozone layer is a layer of ozone particles scattered between 19 and 30 kilometers up in the earth’s atmosphere. Without the ozone layer, UV radiation would not be stopped from entering the earth’s atmosphere and coming to the surface. Cancer would break out and all of the living civilizations, and all species on earth would be in jeopardy.
Ozone is made up of three oxygen atoms (O3). It is poisonous to breath in more than a tiny amount of it. It is made when oxygen (O2) in the stratosphere is broken down by sunlight. The oxygen atoms then join with other oxygen molecules to form O3 or Ozone. The ozone is then broken down again to join with more oxygen. This continuous cycle keeps ozone at it’s correct level.
In the 1970’s, scientists first discovered that chlorofluorocarbons (CFC’s) potentially could destroy the ozone layer, and since CFC’s had been in use as refrigerants, coolants, and propellants for aerosol cans since the 1930’s, there was could have a lot of damage already done. However, only in the 1070 s, the dramatic loss of ozone in the lower stratosphere over Antarctica was first noticed.
Over Antarctica, 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, but also compounds containing bromine, other related halogens and also nitrogen oxides (NOx).
The Ozone Layer
Ozone is a naturally occurring trace gas, chemical formula O3. In the stratosphere, it serves to absorb many harmful solar UV rays.
The atmosphere is about 1000 km (600 miles) thick. Atmospheric layers, as measured in distance from the Earth’s surface, are:
Troposphere (0 to 10 km; 0 to 6 miles)
Stratosphere (10 to 50 km; 6 to 30 miles)
Mesosphere (50 to 80 km; 30 to 50 miles)
Thermosphere (80 to 600 km; 50 to 400 miles)
Exosphere (600 to 1000 km; 400 to 600 miles)
The public s attention is caught mostly by the stratospheric ozone layer and its ability to absorb ultraviolet (UV) light. The ozone layer shields the Earth’s surface from the full fury of solar UV radiation. In the process, ozone is created and destroyed, breaking up into diatomic oxygen and an oxygen atom:
O3 + UVO2 + O (equation 1)
Diatomic oxygen can also be split by UV light to yield two oxygen atoms:
O2 + UVO + O (equation 2)
Ozone is resynthesized by the combination of diatomic oxygen and one of the oxygen atoms liberated in equation 1 or equation 2:
O2 + OO3 (equation 3)
Ozone is depleted when the natural balance is tampered with by humans. UV rays are normally used up in the natural process of producing and destroying ozone. When an unnatural substance destroys ozone and is not used up by the cycle (acts as a catalyst).
This means more ozone is broken down than being created and ultra-violet rays are no longer all absorbed and therefore travel through to our atmosphere more easily. Some substances which can react in such a way with ozone are:
· carbon tetrachloride
CFCs are broken down by ultra-violet rays. This process releases chlorine. The chlorine attaches itself to an ozone molecule and then this newly formed molecule breaks up into an oxygen molecule and a chlorine monoxide molecule. The chlorine monoxide molecules in turn attaches itself to an oxygen atom. This new molecule breaks down forming an oxygen molecule and a chlorine atom and so the process starts again.
The first step requires the breakdown of CFCs by UV light into a reactive chlorine atom:
CFCl2 + UVCFCl + Cl (equation 4)
The next step involves attack on ozone by the chlorine atom
Cl + O3ClO + O2 (equation 5)
Chlorine regenerated in equation 6 may feed back into equation 5. (The oxygen atom is from equations 1 or 2.)
ClO + OCl + O2 (equation 6)
This chlorine atom, which can recycle thousands of times, allows one CFC molecule to break down thousands of ozone molecules. The chlorine atom exists longer at Antarctic stratospheric temperatures, yielding more ozone destruction.
The most important reactions in the destruction of ozone are:
CCl + ClONO2 -> HNO3 + Cl2 (1)
ClONO2 + H2O -> HNO3 + HOCl (2)
HCl + HOCl -> H2O + Cl2 (3)
N2O5 + HCl -> HNO3 + ClONO (4)
N2O5 + H2O -> 2 HNO3 (5)
From the reactions above, note that only molecular chlorine (Cl2) is produced, however, to destroy ozone it is required atomic chlorine.
The molecular chlorine is split by sunlight which lead to the sudden destruction of ozone.
The following diagram shows a schematic illustrating the life cycle of the CFCs; how they are transported up into the upper stratosphere/lower mesosphere, how sunlight breaks down the compounds so they can destroy ozone.
The Ozone Layer
One of the main issues that worry people is the fact that the ozone layer is growing smaller at a steady rate, therefore increasing the size of holes and increasing our chance of health problems.
It can be said that humans are responsible for most of the destruction of the ozone layer. It is now becoming a great concern, and solutions are being provided. However, humans are still using products that contain CFC s and other pollutants. In the following graphs, it is obvious who is responsible for this damage and how it is already affecting some of the planet s living things.
Even though, saving the ozone layer is an issue that is concerning everyone, changing the way of life for some companies is a very expensive task, even if it is for a great and necessary cause.
Company CFC Quantities Cost Cost/lb.
FFord Motor Company 975 tons $9 million $.21
IBM 6,500 tons $10 million $.01
The Ozone Layer
Evaluation of Data
From the data obtained, it can be said that chlorine is a natural threat to ozone, whereas CFC’s are a man-made problem. CFC’s contain one fluorine atom, one carbon atom, and three chlorine atoms. When UV radiation hits a CFC molecule it causes one chlorine atom to break away. The chlorine atom then hits an ozone molecule consisting of three oxygen atoms and takes one of the oxygen molecules, destroying the ozone molecule and turning it into oxygen. When an oxygen molecule hits the molecule of chlorine monoxide, the two oxygen atoms join and form an oxygen molecule. When this happens, the chlorine atom is free and can continue to destroy ozone. Naturally occurring chlorine has the same effect in the ozone layer, but has a shorter life span.
The ozone hole is growing every day. In 1996, it was about 8.3 million square miles on average in size. We account for between 75% and 85% of the ozone depletion that takes place each year. Compared to the 15% to 20% by natural sources, and the 1% to 5% from volcanoes each year, we are the guilty party. Without our involvement, the ozone would be much more stable than it is now
A unique case in the Antarctic in December of 1994 showed us what is to come from our ozone hole. Penguins nesting in Bacharcaise Island had to travel as far as 200 miles offshore and some had to hunt for up to nine days straight for food. Almost all of the penguins returned without food. That summer, only about ten of the 1,800 penguin chicks that hatched on the island survived. The others died of starvation. It is believed that the reduced phytoplankton levels at the bottom of the food chain led to a reduced krill level. When it came to penguins, their food source, the krill, was depleted so there wasn’t enough food to support the natural penguin population.
The Ozone Layer
Practical Applications/Societal Problems
The study of the ozone layer and what to do to save is not only a choice research, but also a necessary issue that has to be completely understood, so that the life on earth is not jeopardized.
We need ozone as it protects us from the harmful ultra-violet rays produced by the sun. There are three different types of ultra-violet rays:
· UV-A which is almost harmless
· UV-B which is more harmful
· UV-C which is deadly to any living thing.
When UV-C gets through the layer of ozone to our atmosphere, it may cause an increase in:
Ø eye cataracts
Ø skin cancer
The main problem that faces society is the use of CFC s and how it has to be stopped. Pollutants come from all over the place, and since they are discovered now, people around the world are trying to avoid them.
The chemical industry didn t know at first that CFC s were harmful to human life. CFC’s used to be used to cheaply clean electronic circuit boards. Being stable, harmless to humans, they were thought of as a perfect cleaning solution, and by the 1970’s, CFC cleaning was used in huge quantities. It was a very costly process to make industries get rid of their CFC s and change their use to ozone-safe methods that are not only more environmentally friendly, but they have reduced the defect ratio in electronic products.
Another ozone layer pollutant is transportation aircraft that we use today for mass-transit. High-speed supersonic airplays that fly high in the stratosphere are potentially dangerous to the ozone located in the upper stratosphere. A fleet of high speed commercial airplanes would be estimated to deplete the ozone layer by only about 2% a year, but it is still a contributing factor in a much bigger problem. The gasses from the exhaust from planes flying in the upper stratosphere can stay in the stratosphere for up to two years, so the life span of them is very short-lived compared to those of CFC’s.
Effects of the ozone hole in Antarctica have already been seen in some of the organisms. Most of the Antarctic organisms have a low tolerance for UV radiation since for most of the year, hardly any direct sunlight reaches the southern-most continent. With the reduced ozone, UV-B radiation has been able to penetrate the atmosphere with a higher intensity. Already, on the base of the Antarctica food chain, an impact has been felt. UV-B radiation has already reduced the plankton populations by between 6% and 12%. That means 6-12% less food at the start of the food chain. Consequently, species higher up have felt the impact.
The Ozone Layer
The ozone hole is here to stay for at least about 50 years before the ozone levels will start to return to their normal levels. Many ideas of trying to manually repair the ozone hole have been looked at. The most obvious solution would be to manually add ozone to the depleted areas of the stratosphere. Unfortunately, that is not a feasible solution. From what we do know about the Antarctic stratospheric mechanics, the ozone levels have worked out a balance even with depleted levels. Any ozone that we would artificially add would most likely be destroyed and would not help our problem in the long run. A more futuristic approach is to destroy the CFC’s when they are in the troposphere with high-powered infrared lasers located on mountainsides. CFC molecules can absorb up to 30 infrared photons before they are destroyed, so a powerful blast would have to be a maintained. It is thought, however, that the infrared laser beams would be shifted out of the needed frequency range before they got to the level of the atmosphere where the CFC’s were targeted to be destroyed. Another possible plan is to dump about 50,000 tons of ethane or propane into the Antarctic stratosphere each spring. The chemicals would transform active ozone-depleting chlorine into non-ozone depleting HC1. The hydrocarbons (propane and ethane) unfortunately would decompose in about a year, so this expensive process would have to be repeated annually. Right now, there are no official plans to try to “fix” the ozone hole in the Antarctic because we don’t know enough about stratospheric mechanics to do so. Our trying to fix the problem might make the problem even worse, or impossible to repair. For now, we are stuck with an ozone-depleted Antarctic.
In the meantime, there are small things that contribute to eventually saving the ozone layer.
These gases are found in:
· aerosol cans, fridges, styrofoam packaging, air-conditioning units
The most obvious way to deplete the levels of CFCs is to:
· stop buying aerosols
· stop buying other CFC-containing products
· if you are dumping a fridge etc., have the CFCs removed
The ozone layer has been a thing we depended on ever since the first sign of life existed on this planet. It is a privilege that is essential to our survival, yet we have abused it and now, the Ozone Hole is a big dilemma that we are facing. It is important for people to realize that the ozone layer is not going to last forever in the rate that it is disappearing, and contributing to the enviroment by avoiding the use of CFC s can contribute to saving our environment.
Ø Grolier Multimedia Encyclopedia, Ozone Layer, Grolier Inc, 1993
Ø The Columbia Encyclopedia, Ozone Layer, 1993
Ø The World Book Encyclopedia, Ozone Layer, 1989
Ø Photos to Go- www.photostogo.com/default.htm
Ø UVB radiation underneath an ozone hole-http://www.atm.amtp.cam.ac.uk/people/mgb/ozonehole.html
Ø The Ozone Hole- www.atm.ch.cam.ac.uk/tour/
Ø Ozone Depletion- www.geocities.com/RainForest/Vines/4030/index.html
Ø The ozone layer- www.schwaben.de/home/kepi/ozone2.htm
Ø Ask Jeeves Encyclopedia- aj.encyclopedia.com/articles/09731.html