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Ozone layer
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It was in 1980 that scientists first noticed how human activities were causing harmful effects on atmospheric ozone. The stratosphere, which is the Earth's second-lowest atmospheric layer, contains about 90 percent of all atmospheric ozone.
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[edit] Forecasts
Recently, however, a new study based on the U.S. National Oceanic and Atmospheric Administration (NOAA) data found evidence that the Earth's ozone layer was getting mended. The study was based on 25 years of independent ozone observations at different altitudes in the Earth's stratosphere, which lies between 9.6 and 50 kilometers above the surface. The ozone level, it has been forecast, would be restored to the 1980 one by the middle of this century.
On the other hand it has also been predicted that the Antarctic ozone hole will reach sizes of 8-10 million square miles nearly every year until about 2018, which is larger than the North American continent. It is, however, certain that the ozone hole is still fragile and needs all our attention.
Environmental issues are of prime concern today. But whereas hazardous waste, Acid rain etc are more or less localized issues, ozone depletion stands to affect the whole world. In the absence of the ozone layer a hostile atmosphere would be created on the planet which would be harmful for humans, and lead to all kinds of skin cancer.
[edit] Ozone Depletion Causes
There are three main contributors to the ozone problem: human activity, natural sources, and volcanic eruptions
- Human activity – 75-85%
- Natural sources – 15 -205
- Volcanic eruptions – 1-5%
Human activity, such as the release of various compounds containing chlorine or bromine, accounts for approximately 75 to 85 percent of ozone damage. Perhaps the most evident and destructive molecule of this description is chloroflourocarbon (CFC). CFCs were first used to clean electronic circuit boards, and as time progressed, were used in aerosols and refrigerators and air conditioners. When CFCs from these products are released into the atmosphere, the destruction begins. Check out this video Under the Counter Ozone Depletion for a visual representation about what causes ozone depletion
A common natural source of ozone damage is naturally occurring chlorine, like the chlorine released from the reaction between a CFC molecule and UV radiation. Finally, during large volcanic eruptions, chlorine, as a component of hydrochloric acid (HCl), is released directly into the stratosphere, along with sulfur dioxide. In this case, sulfur dioxide is more harmful than chlorine because it is converted into sulfuric acid aerosols. These aerosols accelerate damaging chemical reactions, which cause chlorine to destroy ozone.
[edit] Ozone Depleting Substances
In the 1970s there was a marked increase in international concern about ozone depletion which led several countries to ban the use of ozone depleting substances such as aerosol repellents. In 1985, The Vienna Convention was adopted in order to formalize international cooperation on the need to stop using ozone-depleting substances. The Montreal Protocol signed in Montreal, Canada in 1987 aimed to forge more cooperation on the need to phase out ozone depleting substances
Following the Montreal Protocol further studies revealed that there was greater damage to ozone layer than was originally expected. Reacting to this the world governments in 1992 deciding to completely end production of ozone depleting compounds, such as halons, at the beginning of 1994 and CFCs by the beginning of 1996.
What are ozone depleting substances (ODS) used for?
The following are the common usage of CFCs and HCFCs:
- CFC-11, CFC-12 and HCFC-22
as cooling agents in home refrigerators, retail store refrigeration systems, chillers and air-conditioners.
Depending on the make, model and age of your vehicle, the air-conditioning system can be modified to use the ozone friendly refrigerant. The extent and cost of retrofit depends on the system design and the alternative refrigerant chosen.
- CFC-11 and CFC
as propellants for aerosol sprays such as hair mousses and household cleaning products.
- CFC-11 and CFC-12
as blowing agents in the manufacture of foams for home furnishing, insulation and packaging. Some plastics may be shaped using CFCs, e.g. egg cartons, cups and cartons used in fast food operations. Rigid or semi-rigid foams are also used as thermal or sound insulation in refrigeration equipment, buildings and automobiles.
- CFC-113
as a solvent for cleaning electronic circuit boards and computer components. Halons are used as fire extinguishing agents. Bromochlorodifluoromethane (BCF) is commonly used in portable fire extinguishers. Bromotrifluoromethane (BTM) is used in fixed fire-fighting installations. 1, 1, 1-trichloroethane is commonly used as a:
- solvent for cleaning electronic circuit boards and metal work such as watches and clockworks.
- thinner such as that for correction fluid.
- cleaning agent in the textile industry (dry cleaning).
Carbon tetrachloride is used as a cleaning agent in textile and electronics industries.
See - OZONE DEPLETING SUBSTANCES AND OTHER HALOCARBONS REGULATION and also Legislation and regulations: ozone and synthetic greenhouse gases
[edit] Be Ozone Friendly
Every individual is required to take an active part in reducing ozone depletion caused by the products that they buy, the appliances and equipment that their households use. Buy products (aerosol spray cans, refrigerators, fire extinguishers, etc.) whose labels indicate that they are not made with ozone depleting substances. CFC and HCFC refrigerants, portable halon fire extinguishers etc should be replaced with ones which do not contain these harmful chemicals.
Can We Get Rid of the ODS?
Over the last few years, non-ozone-depleting substitutes for ODS are available in the market. For air-conditioning and refrigeration applications CFC-12 can now be replaced by HFC-134a. An emerging market for "drop-in" replacement for CFC and halons is also there.
Some of the alternative products or processes are as follows:
- alternative insulating materials
- substitute food containers such as hydrocarbon blown polystyrene, plastic film wrap and bags
- alternative packaging materials such as plastic film bubble wraps
- air-conditioning and refrigeration plants operating on non-CFC refrigerants.
Replacements for CFC solvents are also available for some applications. For instance, petroleum solvents can be selected as a replacement for CFC-113 or 1, 1, 1-trichloroethane in cleaning applications. Aqueous cleaning, or even no-clean technology, is also an alternative processes that can be used by the electronics industry. Hydrocarbons (e.g. propane and butane) are being used as propellants instead of CFCs in many household products such as paint sprays and insecticides. It is also possible to use Dimethyl ether as propellants replacing CFCs.
[edit] International Commitments
- 1985: Vienna Convention for the Protection of the Ozone Layer calls for voluntary measures to reduce emissions of ozone-depleting substances (ODS).
- 1987: Montreal Protocol on Substances that Deplete the. Ozone Layer establishes a schedule to reduce the production and consumption of CFCs and Halons.
- 1990,92,97: At meetings in London, Copenhagen and Montreal, Parties approve amendments to the Montreal Protocol to stipulate/accelerate the phase-out schedules and add additional ozone-depleting substances to the list.
Achievements
- Between 1986 and 1997, production and Consumption of CFCs fell by 86% and of Halons by 70%
- Atmospheric concentration of Chlorine, which had peaked in 1994, is now declining.
- Millions of Eye Cataracts and Skin Cancer cases averted
- Recovery of the Ozone Layer expected by the year 2050, if the protocol is fully implemented by all Parties.
[edit] How We Can Help to Protect the Ozone Layer
While the vast majority of ODS usage is either industrial or commercial, individuals can help in the following ways:
- Use air-conditioning equipment which does not include CFC as refrigerant.
- Prevent refrigerant leakage by conducting regular inspection and maintenance of air-conditioning and refrigeration appliances.
- If you already posses an air-conditioning and refrigeration appliances that operate on CFCs, consider replacing such equipment to operate on non-CFC refrigerant.
- When motor vehicle air-conditioners need servicing, make sure that the CFC refrigerants are properly recovered and recycled instead of being vented to the atmosphere.
- If you are using CFC-113 as solvent or cleaning agent, ensure that evaporation losses are minimized and the waste solution is recycled as far as possible. You may also try aqueous cleaning as an alternative strategy.
[edit] REFERENCES
- Stop ozone depletion through international cooperation
- Prevention of Ozone Depletion
- Ozone Layer Protection and You
[edit] Useful Sites
The Ozone Hole Tour
The Ozone Hole Tour
