Earth’s atmosphere is divided into three regions, namely troposphere, stratosphere, and mesosphere. The stratosphere extends from 10 to 50 km from the Earth’s surface. This region is concentrated with slightly pungent smelling, light bluish ozone gas. The ozone gas is made up of molecules each containing three atoms of oxygen; its chemical formula is O3. The ozone layer, in the stratosphere acts as an efficient filter for harmful solar Ultraviolet B (UV-B) rays Ozone is produced and destroyed naturally in the atmosphere and until recently, this resulted in a well-balanced equilibrium Ozone is formed when oxygen molecules absorb ultraviolet radiation with wavelengths less than 240 nanometers and is destroyed when it absorbs ultraviolet radiation with wavelengths greater than 290 nanometers. In recent years, scientists have measured a seasonal thinning of the ozone layer primarily at the South Pole. This phenomenon is being called the ozone hole.
Ozone is highly reactive and easily broken down by man-made chlorine and bromine compounds. These compounds are found to be most responsible for most of ozone layer depletion. The ozone depletion process begins when CFCs (used in refrigerator and air conditioners) and other ozone-depleting substances (ODS) are emitted into the atmosphere. Winds efficiently mix and evenly distribute the ODS in the troposphere. These ODS compounds do not dissolve in rain, are extremely stable, and have a long life span. After several years, they reach the stratosphere by diffusion. Strong UV light breaks apart the ODS molecules. CFCs, HCFCs, carbon tetrachloride, methyl chloroform release chlorine atoms, and halons and methyl bromide release bromine atoms. It is the chlorine and bromine atom that actually destroys ozone, not the intact ODS molecule. It is estimated that one chlorine atom can destroy from 10,000 to 100,000 ozone molecules before it is finally removed from the stratosphere. When ultraviolet light waves (UV) strike CFC* (CFCl3) molecules in the upper atmosphere, a carbon-chlorine bond breaks, producing a chlorine (Cl) atom. The chlorine atom then reacts with an ozone (O3) molecule breaking it apart and so destroying the ozone. This forms an ordinary oxygen molecule (O2) and a chlorine monoxide (ClO) molecule. Then a free oxygen** atom breaks up the chlorine monoxide. The chlorine is free to repeat the process of destroying more ozone molecules. A single CFC molecule can destroy 100,000 ozone molecules.
... 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 ... the exhaust from planes flying in the upper stratosphere can stay in the stratosphere for up to two years, so the life ...
Scientist measure ozone layer thickness by measuring how much ultraviolet radiation reaches the ground, using a Dobson ozone spectrophotometer. Ozone layer thickness is measured in Dobson units. The higher the number, the thicker the ozone layer. Since the 1970s, gases produced for commercial purposes have been destroying the ozone layer, upsetting the natural equilibrium that existed. It is planned that by 2005 in developed countries and by 2015 in developing countries, the use of ozone depleting gases, such as CFCs, will be phased out.
He discovered this at the University of Basel in Switzerland. Ozone is merely oxygen, but not the type we breathe. Ozone O3 has three compounds while oxygen has only two. Ozone is reactive, meaning it does not stay still, and wants to go back to its original state, with two compounds, O2. This is why ozone is harmful. Ozone always wants to let go of its third compound, and if this compound reacts with other substances, it could be damaging, especially to humans. When discussing with the ozone layer, one should know the four major atmosphere levels on earth. The troposphere is between zero and fifteen kilometers in altitude and has temperature ranges from 200 to 290 km Kelvin’s. The second is the stratosphere that ranges from fifteen to approximately fifty kilometers in altitude and has temperature ranges from two hundred to two hundred fifty kelvins. The third level in the atmosphere is the mesosphere. This level ranges from 50 to 85 km in altitude and has temperature ranges between 180 and 250 kelvins. Finally, the thermosphere is the final level in the atmosphere. Its range is 85f to 140 km and temperatures as high as 460 kelvins.
ChloroflourocarbonsChloroflourocarbons were discovered in the 1920's by Thomas Midgley, an organic chemist at General Motors Corporation. He was looking for inert, non-toxic, non-flammable compounds with low boiling points that could be used as refrigerants. He found what he was looking for in the form of two compounds: dichlorodifluoromethane (CFC-12) and (CFC-11). In both compounds, different ...
Society has been widely addressed with the many problems in our environment. A major problem is that of Chlorofluorocarbons, CFCs, which are found in many of the aerosol spray cans. In December of 1973, Rowland and Molina discovered that CFCs could destroy the ozone in the stratosphere. In June 1975, the Natural Resources Defense Council (NRDC) sued the Consumers Product Safety Commission for a band of CFCs used in aerosol spray cans. United States’ 5th largest manufacturers of aerosol sprays announced that they would reduce the amount of CFCs used in their products. However, as things started to get better, the Consumer Product Safety Commission rejected NRDC’s lawsuit in July stating that there was insufficient evidence towards the amount of harm the CFCs were doing to the ozone layer. On September 1976, a report was released which re-enforced Rowland and Molina’s hypothesis, but also stated that the government action on CFC regulations should be postponed. This report also stated that the CFCs could initiate climatic changes and contribute to the warming of the earth’s atmosphere, i.e., the greenhouse effect. On May 1977, several government agencies announced joint plans to limit, but not eliminate uses of CFCs in aerosol spray cans.
Nevertheless, on February of the following year, the government decided to postpone the regulations on CFCs used in refrigeration, air conditioning, solvents, and other industrial processes. With all the new regulations taking affect and being postponed, nothing was getting accomplished, but finally, on October 1978, aerosols were banned in the United States. On August of 1981, satellite pictures showed that over one % of the ozone was lost due to CFCs. Then, in October of 1984, research groups found a 40 % loss of ozone over Antarctica. In August of 1985, satellite photos confirmed the existence of an ozone hole over Antarctica. Even though many were trying to reduce the amount of CFCs in their products, there were still some out there, who wanted to make the fast buck. During February 1988, three US senators asked Du Pont to stop making CFCs but the chairperson denied the requested. Three weeks later, the chairperson agreed to ease manufacturing of chemicals, but only when substitutes were available. Eight in a million of the widely scattered molecules are ozone in our atmosphere–this is what is responsible for the rising of global temperature. Ozone takes in ultra-violet rays when they come from the sun and converts the radiation to heat and chemical energy.
Our planet is in danger. Humans have been living on this planet for two million years and in the last two hundred years humans have made a mess of the planet: chopped trees, killed animals, polluted air, water and soil, etc. That is why now we have a lot of ecological problems like the greenhouse effect, extinct and endangered animals and plants, water, air and soil pollution, holes in the ozone ...
The ozone layer also seals earth from the many of the other powerful radiation rays that the sun gives off. Splitting of oxygen molecules depends upon intense radiation; therefore, the greatest ozone production is over the tropics. The ozone is dangerous to us because is causes many types of skin cancer such as malignant melanoma–a very deadly cancer which causes death to 40% of all recorded cases of cancer. Many people predict that the ozone layer would cause 30,000 skin cancers just in the United States alone, and over 500,000 worldwide. Cancer, though, is only one of the few problems that the ozone layer causes. For example, small organisms such as plankton in the sea which is the aquatic food which serves as the basic food chain would be destroyed and therefore destroying the food chain–not only the sea food chain, but also the land. Nobody knows what exact reaction there may be if the ozone continues to break down as it is now. Besides rays from the sun, photon can also come in the Earth and be destructive. Outer portions of the atmosphere, i.e., the thermosphere, the energy from the photon is used to photodisociate (break down) oxygen molecules. Ozone is an unstable compound, if it is left to itself it will turn into O2, but this takes place very slowly in the presents of light. Air pollution increases ozone destruction as show below. NO, nitrogen oxide is air pollution. The troposphere has too much ozone and ozone is harmful to us if is too close. Ten to fifteen molecules per million of ozone in the atmosphere is enough to kill small animals. Since the number is eight per million already, it is not long until it will get extremely destructive. Shown below is how ozone can be created, ozone being O3 and NO2 being pollution. The hole in the ozone layer is become bigger every day. If we do not do anything to stop it, it will eventually kill us. There is so much we can do but we must be willing to do it.
The three most significant problems we face as a nation in the next fifty years are pollution, gun control, and terrorism. Pollution Much of the world's air, water, and land is now partially poisoned by chemical wastes. Some places have become uninhabitable. This pollution exposes people all around the United States to new risks from disease. Many species of plants and animals have become ...
1. Auliciems, Andris and Ian Burton. Perception and Awareness of Air Pollution in
Toronto. Working Paper No. 3. University of Toronto, 1970.
2. Fishman, Jack, and Robert Kalish. Global Alert: The Ozone Pollution Crisis. New York:
Plenum Press, 1990
3. Mainwaring, S. J., and W. Strauss. Air Pollution. Baltimore: Edward Arnold, 1984
4. Oxtoby, David W., Norman H. Nachtribe and Wade A. Freeman. Chemistry: Science of
Change. Toronto: Saunders College Publishing, 1990.
5. Roan, Sharon. Ozone Crisis: The 15-Year Evolution of a Sudden Global Emergency.
Toronto: John Wiley & Sons, Inc., 1989.
6. Young, Louise B. Earth’s Aura. First Edition. New York: Alfred A. Knopf, Inc., 1977.