Thedefinition of The effects of ozone depletion the ozone layer Teamwork Resources The main ozone- The ozone depleting substances analysis The importance of the ozone layer
The definition of the ozone layer:The ozone layer is a layer in Earths atmosphere which contains relatively high concentrations of ozone (O3). Thislayer absorbs 97–99% of the Suns high frequency ultraviolet radiation, which damages the life forms on Earth. It ismainly located in the lower part of the stratosphere from approximately 20 to 30 kilometers (12 to 19 mi) aboveEarth, though the thickness varies seasonally and geographically. The ozone layer was discovered in 1913 by theFrench physicists Charles Fabry and Henri Buisson. Its properties were explored in detail by the Britishmeteorologist G. M. B. Dobson.The ozone analysis (Chlorofluorocarbons and ozone):Many people have heard that the ozone hole is caused by chemicals called chlorofluorocarbons or CFCs. CFCsspread into the atmosphere from refrigeration and propellant devices. In the lower atmosphere, they are so stablethat they last for years, even decades. This long lifetime allows some of the CFCs to reach the stratosphereeventually. In the stratosphere, ultraviolet light breaks the bond holding chlorine atoms (Cl) to the CFC molecule. Afree chlorine atom goes on to participate in a series of chemical reactions that both destroy ozone and return thefree chlorine atom to the atmosphere unchanged, where it can destroy more and more ozone molecules. While thechlorine atoms freed from CFCs do ultimately destroy ozone, the destruction doesn’t happen immediately. Most ofthe roaming chlorine that gets separated from CFCs actually becomes part of two chemicals that—under normalatmospheric conditions—is so stable that scientists consider them to be long-term reservoirs for chlorine.
The importance of the ozone Layer:The Ozone Layer acts as a shield for us from very harmful UV rays. If we damage the Ozone Layer any more, wewill put ourselves at an increasingly greater risk.Without the Ozone Layer we wouldnt be able to survive. UV rays cause skin cancer, damage crops, and harmocean life. Without the Ozone Layer the risk of these things would greatly increase. An example of this is inAustralia, where a large amount of ozone has depleted. Around 97% of the citizens have or have had skin cancerproblems due to the exposure to harmful UV rays that leak through the Ozone layer. Another risk is polar shifting; acomplex event occurs when uneven melting of ice shelves occurs. A major hole is now over Antarctica, wherethere are ice shelves. If these ice shelves melt, there could be increase coastal flooding and the poles could shift,causing a violent shift in climate.The Main Ozone-Depleting Substances (ODS): • Chlorofluorocarbons (CFCs) The most widely used, accounting for over 80% of total stratospheric ozone depletion. • Used as coolants in refrigerators, freezers and air conditioners in buildings and cars manufactured before 1995. • Found in industrial solvents, dry-cleaning and hospital sterilizers. • Also used in foam products — such as soft-foam padding (e.g. cushions and mattresses) and rigid foam (e.g. home insulation). • Halons (compound gases that damage the ozone layer) • Used in some fire extinguishers, in cases where materials and equipment would be destroyed by water or other fire extinguisher chemicals. Halons cause greater damage to the ozone layer than do CFCs. • Methyl Chloroform Used mainly in industry: in vapor degreasing, cleaning, adhesives and chemical processing. • Carbon Tetrachloride • Used in solvents and some fire extinguishers. • Hydro fluorocarbons (HCFCs) • HCFCs have become major, “transitional” substitutes for CFCs. They are less harmful to stratospheric ozone than CFCs are. But HCFCs still cause some ozone destruction and are potent greenhouse gases.
The effects of ozone depletion are:1- The depletion of the ozone layer and the resulting increase in ultraviolet radiation may lead to accelerate therate of the smog, which remains suspended in the air for several days, as happened in London in 1952, when therewas haze atmosphere of this city, during days to nights over a few days, and led to heavy loss of life, It got to about4 thousand deaths.2- Perhaps the most affected areas are the tropical region, a result of high temperature, and the power of the sun.As some research suggests that half of the plants exposed to radiation UVB, reduced production and smaller sizeof their leaves, affecting the production of agricultural crops.3- As it is explained in some reports, that there is potential for soybean production decreased by 23% as a result ofexposure to this type of radiation. Add to that the chemical compositions, for some types of plants, may changebecause of this situation, to the detriment of their content of minerals and nutritional value.4- The ultraviolet rays of the type of UVB, plays a major role in the formation of skin diseases, and that means analmost 300 thousand cases of skin cancer every year.5- Some disease such as: cataracts in the lens of the eye, in addition to injuring the eye disease glaucoma, inwhich the eye is unable to resist these rays, and that weakens the effectiveness of the immune system in humans,and this is what makes people more susceptible to infectious diseases, caused by viruses such as scabies, as wellas the resulting Tuberculosis as a disease by bacteria.6- Do not stop the negative effects of reducing the ozone layer on humans alone, Contributes destruction of theozone layer and the widening hole in this layer to increase the temperature of the earths surface, and thus lead tothe so-called global warming.7- On the other hand, there are fears of a weakening of clusters of micro-organisms in the seas and oceans, knownas plankton plant, because of exposure to UV radiation. These objects are an important basis for the food chain inecosystems in fresh and salt water, primarily fish. Resources
1-http://www.research.noaa.gov/climate/t_ozonelayer.html 2-www.oar.noaa.gov/climate/t-ozonelayer.html Teamwork: Editor: Hala Alnashed Designer: Batool Abdeen Publisher: Marwa Attar& Afaf Alkhalil Alkods High School/Grade: Second secondary scientificSupervisor: Mrs. Tonia Bitar Toniabitar@gmail.com