Ozone layer depletion


Chlorofluorohydrocarbons (CFCs) are good fire fighting agents, but when released cause depletion of the ozone layer, which in turn contributes to global warming. CFG systems are gradually being phased out of the oil and gas industry, and are being replaced by less harmful alternatives.  [c.74]

Measurements of ozone (O3) concentrations in the atmosphere are of particular importance. Ozone absorbs strongly in the ultraviolet region and it is this absorption which protects us from a dangerously high dose of ultraviolet radiation from the sun. The vitally important ozone layer lies in the stratosphere and is typically about 10 km thick with a maximum concentration about 25 km above the surface of the earth. Extreme depletion of ozone in a localised part of the atmosphere creates what is known as an ozone hole.  [c.380]

Montreal Protocol on Substances that Deplete the Ozone Layer," Sept. 16, 1987 Code Fed. R.eg, Tide 40, Part 82, U.S. EPA, Washiagton, D. C., 1988.  [c.106]

Depletion of the Ozone Layer. As a constituent of the atmosphere, ozone forms a protective screen by absorbing radiation of wavelengths between 200 and 300 nm, which can damage DNA and be harmful to life. Consequently, a decrease in the stratospheric ozone concentration results in an increase in the uv radiation reaching the earth s surfaces, thus adversely affecting the climate as well as plant and animal life. Pot example, the incidence of skin cancer is related to the amount of exposure to uv radiation.  [c.503]

Confirmation of the destmetion of ozone by chlorine and bromine from halofluorocarbons has led to international efforts to reduce emissions of ozone-destroying CPCs and Halons into the atmosphere. The 1987 Montreal Protocol on Substances That Deplete the Ozone Layer (150) (and its 1990 and 1992 revisions) calls for an end to the production of Halons in 1994 and CPCs, carbon tetrachloride, and methylchloroform byjanuary 1, 1996. In 1993, worldwide production of CPCs was reduced to 50% of 1986 levels of 1.13 x 10 and decreases in growth rates of CPC-11 and CPC-12 have been observed (151).  [c.503]

A smaller factor in ozone depletion is the rising levels of N2O in the atmosphere from combustion and the use of nitrogen-rich fertilizers, since they ate the sources of NO in the stratosphere that can destroy ozone catalyticaHy. Another concern in the depletion of ozone layer, under study by the National Aeronautics and Space Administration (NASA), is a proposed fleet of supersonic aircraft that can inject additional nitrogen oxides, as weU as sulfur dioxide and moisture, into the stratosphere via their exhaust gases (155). Although sulfate aerosols can suppress the amount of nitrogen oxides in the stratosphere  [c.503]

Today s technology manager faces the special challenge of orchestrating a vast array of resources, including many that can be located outside the manager s organizational unit. For example, concern over depletion of the earth s protective ozone layer led to the decision to phase out the manufacture and sale of chlorofluorocarbons. In a matter of five years, the Freon refrigerants business in DuPont was remade into an entirely new Suva refrigerants business. Technology development valued at 400 x 10 in capital and R D resulted in the creation of seven new manufacturing faciUties and dozens of products grouped in five families to replace the six in the Freon (DuPont) business, and also involved the filing of 400 patents. This would not have been accomphshed had not the R D manager created a network of supporting resources that included universities, institutes, customers, and industry consortia. Basic data for synthesis and manufacturing as weU as toxicity and property information came from over two dozen technical resources around the world. The result was the successful re-creation of a 500 x 10 to 1 x 10 business (58).  [c.132]

Although sprays are useful ia numerous commercial applications, they may create some serious environmental problems because of iaefficient atomization or through misuse. For example, there is a growing concern over poUutant emissions from aircraft and automotive engines that utilize atomizers. PoUutants from engines iaclude carbon monoxide, unbumed hydrocarbons, oxides of nitrogen, and smoke. These poUutants can cause photochemical smog, depletion of the ozone layer, acid rain, and other conditions harmful to human life. Atmospheric poUution may also occur ia spray painting and coating processes. Devices used to atomize solvents and coating formulations must be designed to meet air poUution standards. Because of the potential problems associated with sprays, it has become increasingly important to understand the process of atomization. Liquid atomizers must be properly designed and selected to minimize uimecessary hazards.  [c.327]

Ozone Layer was signed, which set a timetable for phasing out the production and use of CFCs, including halons. The date for phaseout of the manufacture of halons according to the latest Copenhagen Meeting was January 1, 1994 (UNEP, Montreal Protocol on Substances that Deplete the Ozone Layer—Final Act 1987, 1987).  [c.2339]

Pollution controls were being built into pollution sources—automobiles, power plants, factories—at the time of original construction rather than later on. Also, for the first time, serious attention was directed to the problems caused by the "greenhouse" effect of carbon dioxide and other gases building up in the atmosphere, possible depletion of the stratospheric ozone layer by fluorocarbons, long-range transport of pollution, prevention of significant deterioration (PSD), and acidic deposition.  [c.15]

The other global environmental problem, stratospheric ozone depletion, was less controversial and more imminent. The U.S. Senate Committee Report supporting the Clean Air Act Amendments of 1990 states, Destruction of the ozone layer is caused primarily by the release into the atmosphere of chlorofluorocarbons (CFCs) and similar manufactured substances—persistent chemicals that rise into the stratosphere where they catalyze the destruction of stratospheric ozone. A decrease in stratospheric ozone will allow more ultraviolet (UV) radiation to reach Earth, resulting in increased rates of disease in humans, including increased incidence of skin cancer, cataracts, and, potentially, suppression of the immune system. Increased UV radiation has also been shown to damage crops and marine resources."  [c.16]

An important effect of air pollution on the atmosphere is change in spectral transmission. The spectral regions of greatest concern are the ultraviolet and the visible. Changes in ultraviolet radiation have demonstrable adverse effects e.g., a decrease in the stratospheric ozone layer permits harmful UV radiation to penetrate to the surface of the earth. Excessive exposure to UV radiation results in increases in skin cancer and cataracts. The worldwide effort to reduce the release of stratospheric ozone-depleting chemicals such as chlorofluorocarbons is directed toward reducing this increased risk of skin cancer and cataracts for future generations.  [c.375]

The new law buUds on the market-based structure and requirements currently contained in EPA s regulations to phase out the production of substances that deplete the ozone layer. The law requires a complete phase-out of CFCs and halons with interim reductions and some related changes to the existing Montreal Protocol, revised in June 1990.  [c.404]

SI 1996/506 Environmental Protection (Controls on Substances that Deplete the Ozone Layer) Regulations  [c.565]

Decision on controlled substances allowed for essential uses in 1998 under Regulation 3093/94 on substances that deplete the ozone layer  [c.566]

Community m 2000 under Council Regulation (ECj No. 3093/94 on substances that deplete the ozone layer  [c.567]

Title VI Stratospheric Ozone and Global Climate Protection - The law builds on the market-based structure and requirements currently contained in EPA s regulations to phase out the production of substances that deplete the ozone layer.  [c.7]

Ozone IS a molecule formed from binding together three oxygen atoms. Gaseous ozone readily absorbs selected frequencies of ultraviolet radiation because ozone molecules have a resonant frequency in the ultraviolet region of the electromagnetic spectrum. A natural concentration of ozone exists twenty to thirty kilometers above Earth s surface. Ozone molecules absorb nearly all ultraviolet radiation from the sun having a wavelength less than about 0.3 micrometers. Accordingly, the natural ozone layer protects humans from harmful effects such as skin cancer. Human-made products migrating into the ozone layer can react with ozone molecules and convert them to other forms that do not absorb ultraviolet radiation. Chlorinated fluorocarbons, CFCs for short, once commonly used m refrigerators and aerosol spray cans, were found to be depleting the ozone, and in 1978 were banned from use m aerosol sprays. Banning the use of CFCs has not totally solved the ozone depletion problem.  [c.1224]

The formed mixture is composed of trichlorofluoromethane (Freon-11) and dichlorodifluoromethane (Freon-12). These compounds are used as aerosols and as refrigerants. Due to the depleting effect of chlorofluorocarbons (CFCs) on the ozone layer, the production of these compounds may be reduced appreciably.  [c.140]

Ozone forms a layer around the Earth that insulates against thermal radiation. This layer is being destroyed by pollutants (principally fluorocarbons). The effect of the depletion of the ozone layer is to warm the Earth (and hence exacerbate the greenhouse effect) and may also lead to an increase in the incidence of skin cancers.  [c.754]

Flexible Foam. Flexible slab or bun foam is poured by multicomponent machines at rates of >45 kg/min. One-shot pouring from traversing mixing heads is generally used. A typical formulation for furniture-grade foam having a density of 0.024 g/cm includes a polyether triol, mol wt 3000 TDI water catalysts, ie, stannous octoate in combination with a tertiary amine and surfactant. Coblowing agents are often used to lower the density of the foam and to achieve a softer hand. Coblowing agents are methylene chloride, methyl chloroform, acetone, and CFG 11, but the last has been eliminated because of its ozone-depletion potential. Additive systems (24) and new polyols (25) are being developed to achieve softer low density foams. Higher density (0.045 g/cm ) slab or bun foam, also called high residency (HR) foam, is similarly produced, using polyether triols having molecular weight of 6000. The use of polymer polyols improves the load-bearing properties.  [c.347]

Propellants such as propane and butane are typically used in these cans nonflammable halocarbons have been almost totally replaced due to the ozone layer depletion problem. The propellants are therefore usually flammable and may create flammable atmospheres when used carelessly in enclosed spaces. After six cans of insecticide had been sprayed a fatal explosion occurred in a ship s small galley after a spark from a refrigerator ignited the propane propellant [49]. Tests were conducted to explain a separate explosion which occurred during a can filling operation [49]. An equipment malfunction caused two cans to empty after the valves had been torn off. It was shown that only cans filled with powder -I- propellant charged sufficiently to cause a static ignition cans filled with liquid -I- propellant produced only moderate charging. In this particular case, the cans had contained dry shampoo. It appeared that one or both cans, being isolated from ground by the plastic transport system, charged to about 35 kV and sparked to a nearby conductive object, perhaps another can. The can s 8.2 pF capacitance gave the maximum stored spark energy as 5 mJ, which will ignite propane-air mixtures over a wide range of flammable compositions. It was considered noncredible that an aerosol spray can could pose an ignition  [c.164]

Helium is also being used to advertise on blimps for various companies, including Goodyear. Other lifting gas applications are being developed by the Navy and Air Force to detect low-flying cruise missiles. Additionally, the Drug Enforcement Agency is using radar-equipped blimps to detect drug smugglers along the United States boarders. In addition, NASA is currently using helium-filled balloons to sample the atmosphere in Antarctica to determine what is depleting the ozone layer.  [c.8]

The importance of ozone in the stratosphere has been stressed in Section 9.3.8. The fact that ozone can be decomposed by the halogen monoxides CIO, BrO and 10 means that their presence in the stratosphere contributes to the depletion of the ozone layer. For example, iodine, in the form of methyl iodide, is released into the atmosphere by marine algae and is readily photolysed, by radiation from the sun, to produce iodine atoms which can react with ozone to produce 10  [c.385]

Concern arose during the 1970s about cumulative CFG emissions iato the atmosphere with progressive depletion of the stratospheric ozone layer by Cl atoms and led to the formation and global support of a multinational fomm, called the Montreal Protocol on Substances That Deplete the Ozone Layer. As a result, CFG production has been dramatically decreased and will likely be totally phased out before the year 2000 (3) (see Fluorinated aliphatics compounds). If hydrogen atoms are introduced into the CFG stmcture to lower the chlorine content, the resulting hydrochlorofluorocarbon (HCFC) is more susceptible to degradation in the lower atmosphere before it can reach the stratosphere. However when a hydrogen atom is introduced into a one-carbon compound, the boiling point is lowered and may be too low for the same CFG appHcation. Therefore two-carbon compounds bearing some hydrogen are more attractive substitutes than the one-carbon modified CFCs. As hydrogen content increases, there is a counter effect of increasing flammabihty, which in turn limits some HCFC appHcations.  [c.266]

Since the area of the solar beam intercepted by the earth is ttE-, where E is the radius of the earth, and the energy falling within this circle is spread over the area of the earth s sphere, 4ttE, in 24 hr, the average energy reaching the top of the atmosphere is 338 W m . This average radiant energy reaching the outer limits of the atmosphere is depleted as it attempts to reach the the earth s surface. Ultraviolet radiation with a wavelength less than 0.18 /urn is strongly absorbed by molecular oxygen in the ionosphere 100 km above the earth shorter x-rays are absorbed at even higher altitudes above the earth s surface. At 60-80 km above the earth, the absorption of 0.2-0.24 /um wavelength radiation leads to the formation of ozone below 60 km there is so much ozone that much of the 0.2-0.3 /rm wavelength radiation is absorbed. This ozone layer in the lower mesosphere and the top of the stratosphere shields life from much of the harmful ultraviolet radiation. The various layers warmed by the the absorbed radiation reradiate in wavelengths dependent on their temperature and spectral emissivity. Approximately 5% of the total incoming solar radiation is absorbed above 40 km. Under clear sky conditions, another 10-15% is absorbed by the lower atmosphere or scattered back to space by the atmospheric aerosols and molecules as a result, only 80-85% of the incoming radiation reaches the earth s surface. With average cloudiness, only about 50% of the incoming radiation reaches the earth s surface, because of the additional interference of the clouds.  [c.246]

COM(98j398 Proposal for a regulation on substances which deplete the ozone layer  [c.567]

COM(99j67 Amended proposal for a Regulation on substances which deplete the ozone layer  [c.567]

To recap, surrounding the earth at a height of about 25 kilometers is the stratosphere, which is rich in ozone, and its purpose is to prevent the sun s harmful ultraviolet (UV) rays from reaching the earth. UV rays have an adverse effect on all living organisms, including marine life, crops, animals and birds, and humans. In humans, UV is known to affect the immune system to cause skin cancer, eye damage, and cataracts and to increase susceptibility to infectious diseases, such as malaria. In 1974, it was hypothesized that chlorinated compounds were able to persist in the atmosphere long enough to reach the stratosphere, where solar radiation would break up the molecules and release chlorine atoms that would destroy the ozone layer. Mounting evidence and the discovery of the Antarctic ozone hole in 1985 led to the global program to control chlorofluorocarbons (CFCs) and other ozone-destroying chemicals. In addition to Antarctica, ozone loss is now present over New Zealand, Australia, southern Argentina and Chile, North America, Europe, and Russia, The ozone-depleting substances (ODSs) of concern are CFCs, halons, methyl chloroform (1,1,1,-trichloroethane MCF), carbon tetrachloride (CTC), hydrochlorofluorocarbons (HCFCs), and methyl bromide. CFC-11 was assigned an ODP of 1.0 all other chemicals have an ODP relative to that of CFC-11. An ODP higher than 1.0 means that the chemical has a greater ability than CFC-11 to destroy the ozone layer an ODP lower than 1.0 means that the chemical s ability to destroy the ozone layer is less than that of CFC-11. In September 1987, the Montreal Protocol on Substances that Deplete the Ozone Layer (the Protocol) was signed by 25 nations and the European Community. The Protocol was the first international environmental agreement, and its signing by so many nations represented a major accomplishment, and a major shift in the approach to handling global environmental problems. The Protocol called for a freeze on the production of halons and a requirement to reduce the production of CFCs by 50% by 1999. However, new scientific evidence surfaced after the entry into force of the Protocol, indicating that ozone depletion was more serious than originally thought. Accordingly, in 1990 (London), 1992 (Copenhagen), and 1995 (Vienna), amendments were made to the Protocol to regulate the phaseout of the original chemicals and the control and phase-out of additional chemicals. The principal provisions of the Montreal Protocol as it now stands are as follows  [c.32]

This site and hotline provides information about the science of ozone depletion, regulations under Title VI of the Clean Air Act Amendments (CAAA) of1990 designed to protect the ozone layer, information on methyl bromide, flyers about the UV index, information for the general public, and other topics. Hours 10 00 a.m. - 4 00p.m., weekdays, EST.  [c.303]

Hydrodchalogenation, the replacement of a halogen atom (usually chlorine) with hydrogen, as applied to alkanes has been the subject of much recent study, because this process gives hydrochlorofluorocarbons (HCFCs) or hydrojluorocarbons (HFCs) These classes of fluorocarbons have far shorter half-lives m the troposphere than do chlorofluorocarbons (CFCs) and are therefore sought as alternatives that make little or no contribution to the depletion of the ozone layer or to global warming. Catalytic hydrogenation of CFCs havmg three chlonne atoms on one  [c.300]

Initial evidence for the effect of chlorofluorocarbons on the ozone layer was very limited, based mamly on computer models of the atmosphere. In the 1970s, there was no observational support for ozone depletion. However, refrigerant producers initiated research programs and identified a number of potential alternatives. The research programs were given renewed impetus in the mid-1980s following pohtical pressure m the United States and the discovery of the ozone depletion over the Antarctic during its spring This was the first observational evidence for the possible effect of chlorofluorocarbons on stratospheric ozone  [c.1092]

The Monitor Top used a toxic refrigerant, sulfur dioxide. In the late 1920s, Frigidaire Corporation, then a leading manufacturer of household refrigerators, asked the General Motors research laboratoi y to develop a refrigerant that is non-toxic and non-flammable. The result was a chlorofluorocarbon (CFC), namely dichlorodifluoromethane, commonly known as Refrigerant 12 of the Freon family. By the time of World War II, it completely replaced sulfur dioxide. In the 1980s, it was discovered that CFCs deplete the ozone layer surrounding the Earth, thus increasing the likelihood of skin cancer. In 1987 the United States joined other industrial nations m signing the  [c.997]

Montreal Protocol on Substances that Deplete the Ozone Layer. The phase-out of CFCs began on Jnly 1, 1989, and by 1997, a hydroflnorcarbon, HFC134a, with zero ozone depletion potential, became the dominant refrigerant in the United States. The phase-out of CFCs in developing countries is on a slower schedule.  [c.998]

United Nations Environmental Program. (1995). Montreal Protocol on Substances that Deplete the Ozone Layer— Report on the. RcBigcration, Air Conditioning and Heat Pumps Technical Options Committee. New York Author.  [c.1003]

Table 1 lA presents tabulations of the safety of important refrigerants, but this list does not include aU available refrigerants. Table 11-5 summarizes a limited list of comparative hazards to life of refrigerant gas and vapor. The current more applicable refrigerants from the m or manufacturers of the CFC and HCFC refrigerants and their azeotropes/ blends/mrxtures are included, but the list excludes the pure hydrocarbons such as propane, chlorinated hydrocarbons such as methyl chloride and others, inorganics, ammonia, carbon dioxide, etc. See Table 11-6. The CFC compounds have a longer and more serious ozone depletion potential than the HCFC compounds, because these decompose at a much lower atmospheric level and have relatively short atmospheric lifetimes therefore, they do less damage to the ozone layer. Table 11-7 summarizes alternate refrigerants of the same classes as discussed previously. Table 11-8 correlates DuPont s SUVA refrigerant numbers to the corresponding ASHRAE numbers. Table 1 lA presents tabulations of the safety of important refrigerants, but this list does not include aU available refrigerants. Table 11-5 summarizes a limited list of comparative hazards to life of refrigerant gas and vapor. The current more applicable refrigerants from the m or manufacturers of the CFC and HCFC refrigerants and their azeotropes/ blends/mrxtures are included, but the list excludes the pure hydrocarbons such as propane, chlorinated hydrocarbons such as methyl chloride and others, inorganics, ammonia, carbon dioxide, etc. See Table 11-6. The CFC compounds have a longer and more serious ozone depletion potential than the HCFC compounds, because these decompose at a much lower atmospheric level and have relatively short atmospheric lifetimes therefore, they do less damage to the ozone layer. Table 11-7 summarizes alternate refrigerants of the same classes as discussed previously. Table 11-8 correlates DuPont s SUVA refrigerant numbers to the corresponding ASHRAE numbers.
Much research is being conducted to find alternatives to CFCs with little or no effect on the ozone layer. Among these are HCFC-123 (HCCI2CF3) to replace Freon-11 and HCFC-22 (CHCIF2) to replace Freon-12 in such uses as air conditioning, refrigeration, aerosol, and foam. These compounds have a much lower ozone depletion value compared to Freon-11, which was assigned a value of 1. Ozone depletion values for HCFC-123 and HCFC-22 relative to Freon-11 equals 0.02 and 0.055, respectively.  [c.140]

Once the sun sets, O formation ceases and, in an urban area, ozone is rapidly scavenged by freshly emitted NO (eq. 3). On a typical summer night, however, a nocturnal inversion begins to form around sunset, usually below a few hundred meters and consequently, the surface-based NO emissions are trapped below the top of the inversion. Above the inversion to the top of the mixed layer (usually about 1500 m), O is depleted at a much slower rate. The next morning, the inversion dissipates and the O -rich air aloft is mixed down into the O -depleted air near the surface. This process, in combination with the onset of photochemistry as the sun rises, produces the sharp increase in surface shown in Figure 1. As shown, the overnight depletion is less in the more mral areas than in a large urban area such as New York City. This is a result of the lower overnight levels of NO in mral areas. Even in the absence of NO or other O scavengers (olefins, for example), O decreases at night near the ground faster than aloft because of its destmction at any surface, ie, the ground, buildings, trees. At the remote mountaintop sites, Whiteface and Utsayantha, there is no overnight decrease in O concentrations.  [c.370]

In this sequence the Cl also acts as a catalyst and two molecules are destroyed. It is estimated that before the Cl is finally removed from the atmosphere in 1—2 yr by precipitation, each Cl atom will have destroyed approximately 100,000 molecules (60). The estimated O -depletion potential of some common CFCs, hydrofluorocarbons, HFCs, and hydrochlorofluorocarbons, HCFCs, are presented in Table 10. The O -depletion potential is defined as the ratio of the emission rate of a compound required to produce a steady-state depletion of 1% to the amount of CFC-11 required to produce the 1% depletion. The halons, bromochlorofluorocarbons or bromofluorocarbons that are widely used in fire extinguishers, are also ozone-depleting compounds. Although halon emissions, and thus the atmospheric concentrations, are much lower than the most common CFCs, halons are of concern because they are from three to ten times more destmctive to O, than the CFCs.  [c.380]

Other reactions, such as the reaction of CIO with NO2 to form chlorine nitrate (CIO + NO2 — CIONO2, are also important. Reaction of N20 on sulfate aerosols forms HNO, reducing the avaUabUity of NO2. This aUows higher free CIO concentrations, shifting ozone catalytic decomposition from NO to CIO and HO (80). Chlorine nitrate and HCl can form temporary inert chlorine reservoirs and retard ozone depletion they are the most abundant chlorine species at lower latitudes before winter. However, CIONO2 can slowly photolyze, yielding chlorine atoms capable of decomposing ozone this accounts for 10—15% of halogen-controUed losses (76). With the exception of NO2, aU radicals are produced photolyticaUy each day and their concentrations faU to zero during the night.  [c.496]


See pages that mention the term Ozone layer depletion : [c.387]    [c.526]    [c.503]    [c.566]    [c.567]    [c.1089]    [c.1092]    [c.1096]    [c.304]    [c.583]   
Chemistry of Organic Fluorine compounds II (1995) -- [ c.300 ]