Ozone layer


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]

Ozone s presence in the atmosphere (amounting to the equivalent of a layer 3 mm thick under ordinary pressures and temperatures) helps prevent harmful ultraviolet rays of the sun from reaching the earth s surface. Pollutants in the atmosphere may have a detrimental effect on this ozone layer. Ozone is toxic and exposure should not exceed 0.2 mg/m (8-hour time-weighted average - 40-hour work week). Undiluted ozone has a bluish color. Liquid ozone is bluish black and solid ozone is violet-black.  [c.21]

One of the chief uses of chloromethane is as a starting material from which sili cone polymers are made Dichloromethane is widely used as a paint stripper Trichloromethane was once used as an inhalation anesthetic but its toxicity caused it to be replaced by safer materials many years ago Tetrachloromethane is the starting mate rial for the preparation of several chlorofluorocarbons (CFCs) at one time widely used as refrigerant gases Most of the world s industrialized nations have agreed to phase out all uses of CFCs because these compounds have been implicated m atmospheric processes that degrade the Earth s ozone layer  [c.167]

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]

Ozone shows two absorption systems, from the X Ai ground state, in the near ultraviolet region. The C-X, Huggins, system is in the region ca 310-3 74 nm and the D-X, Hartley, system in the region ca 220-310 nm, these limits being imprecise because the systems overlap. The Hartley system is very much more intense than the Huggins system and is responsible for the ozone layer being opaque to radiation from the sun in this region.  [c.380]

Measurements of ozone concentration in the ozone layer in the stratosphere are made in the less intense Huggins band to avoid complete absorption of the laser radiation. Again, the two or three wavelength DIAL method is used to make allowance for background aerosol scattering. A suitable laser for these measurements is the XeCl pulsed excimer laser (see Section 9.2.8) with a wavelength of 308 nm, close to the peak absorption of the Huggins  [c.381]

For measurement of ozone concentration using the Huggins band and the three wavelength DIAL method, the extra wavelength is provided by Raman shifting the 308 nm radiation in a high pressure deuterium cell to a wavelength of 339 nm. It is convenient to use a Raman shifting cell containing a mixture of H2 and H2 so that the XeCl laser and only one Raman shifting cell provide the three wavelengths of 308, 339 and 353 nm. This three wavelength DIAL method has proved particularly useful when the aerosol concentration is high, for example when the ozone layer is seriously contaminated as a result of volcanic emption.  [c.382]

Possible negative environmental effects of fertilizer use are the subject of iatensive evaluation and much discussion. The foUowiag negative effects of fertilizer usage have been variously suggested (113) a deterioration of food quaUty the destmction of natural soil fertility the promotion of gastroiatestiaal cancer the pollution of ground and surface water and contributions toward the destmction of the ozone layer ia the stratosphere.  [c.246]

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 from lightning and the ozone layer  [c.2172]

Chlorofluoro- Used in refrigeration and production of Refrigeration, plastic foam production, Attacks stratospheric ozone layer green-  [c.2174]

Haion Systems for Inerting The term halon is generic for a range of h ogenated hydrocarbons in which one or more of the hydrogen atoms have been replaced by atoms from the halogen series. Fiilly halogenated hydrocarbons are considered hard halons because it is believed that they have a major effect on the ozone layer. They work as fire-extinguishing agents by interfering with the free radical chain reaction occurring in flames. However, they destroy ozone in the same way. Halons containing bromine are much more destructive of ozone than chlorofluorocarbons (CFCs). It has been reported that one atom of some halons can destroy lO " ozone molecules. Halon alternatives that have less effect on the ozone layer include HCFCs, which are halogenated hydrocarbons with at least one hydrogen atom. In 1987, the Montreal Protocol on Protection of the Stratospheric  [c.2339]

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]

The stratosphere is of interest to aeronautical scientists because it is traversed by airplanes to communications scientists because of radio and television communications and to air pollution scientists because global transport of pollution, particularly the debris of aboveground atomic bomb tests and volcanic eruptions, occurs in this region and because absorption and scattering of solar energy also occur there. The lower portion of this region contains the stratospheric ozone layer, which absorbs harmful ultraviolet (UV) solar radiation. Global change scientists are interested in modifications of this layer by long-term accumulation of chlorofluorocarbons (CFCs) and other gases released at the earth s surface or by high-altitude aircraft.  [c.20]

One air pollution problem of a global nature is the release of chlorofluoro-carbons used as propellants in spray cans and in air conditioners and their effect on the ozone layer high in the atmosphere. (See Chapter 11.)  [c.38]

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]

As you know, most countries are phasing out certain refrigerants to lessen damage to the ozone layer. The chemicals being phased out are chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). Replacements are hydrofluorocarbons (HFCs) and certain blends. The DuPont web site (www.dupont.com) gives the handy Table I of recommended replacement refrigerants for various applications.  [c.182]

New hydrofluorocarbons (HFCs) are replacing the chlorofluorocarbons (CFCs) and hydrochlorofluorocar-bons (HCFCs) phased out to lessen damage to the ozone layer. The DuPont website lists physical properties for a number of their refrigerants.  [c.386]

Another area of potential interest is in refrigerator liners. The move away from the ozone-layer-damaging chlorofluorocarbons (CFCs) to HCFCs in the USA and pentane/cyclopentane blends in Europe has not been without problems. These newer materials have an adverse effect on ABS whereas the nitrile resin appears satisfactory, if more expensive.  [c.417]

The use of CFCs such as fluorotrichloromethane became quite widespread, particularly as for many years the material was believed to cause few toxic and environmental problems. However, evidence that such materials were damaging the ozone layer became substantial and the use of such materials is to be discouraged and is illegal in many countries. To some extent CFCs have been substituted by methylene chloride (also illegal in some countries) and other fluoro compounds, but these too may prove to be environmentally unacceptable. For this reason there has been increased dependence on the use of the isocyanate-water reaction to generate sufficient carbon dioxide to give products of the required density.  [c.797]

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]

When writing a Lewis structure we restrict a molecule s electrons to certain well defined locations either linking two atoms by a covalent bond or as unshared electrons on a sm gle atom Sometimes more than one Lewis structure can be written for a molecule espe cially those that contain multiple bonds An example often cited m introductory chem istry courses is ozone (O3) Ozone occurs naturally m large quantities m the upper atmosphere where it screens the surface of the earth from much of the sun s ultraviolet rays Were it not for this ozone layer most forms of surface life on earth would be dam aged or even destroyed by the rays of the sun The following Lewis structure for ozone satisfies fhe ocfef rule all fhree oxygens have eighf elecfrons m fheir valence shell  [c.24]

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]

The photochemical degradation of herbicides is dependent on the ability of the herbicide to absorb light at a wavelength between 285 and 400 nm (259,260). Light below these wavelengths is generally absorbed by the earth s ozone layer and does not reach the surface. Light above 400 nm does not have sufficient energy to alter chemical bonds and thus does not photodegrade herbicides. Considerable work is being conducted to investigate the possibility of utilizing photochemical reactions to degrade waste herbicides. Examples of these approaches would include photocatalytic systems, eg, ultraviolet (uv) light plus a photocatalyst ozonation/uv light systems and free-radical generating systems, eg, Fe " /H202 with or without uv  [c.48]

A second force that is seriously affecting etch technology is the move to actively eliminate CFG gases to comply with the Montreal Protocol for protection of the ozone layer. These gases, eg, CFCl, CCI2F2, CF Cl, and CF Br, are being replaced by fluotine-based gases for tungsten etch, such as SF, NF, and SiF chlotine-based gases for A1 etch, eg, CI2, BCl, and SiCl and bromine-based gases, Br2, and HBr. Table 2 Hsts conventional and newer chemistries.  [c.353]

Carbon disulfide for manufacture of carbon tetrachloride increased in the 1950s and 1960s to supply the key raw material for chlorofluorocarbon refrigerants and aerosol propellants. Because of ecological and health concerns, carbon tetrachloride consumption began to decline in the mid-1970s. That use for carbon disulfide will suffer under a United Nations proposal to phase out carbon tetrachloride and chlorofluorocarbons to protect the earth s ozone layer (133). During 1991 the only remaining carbon tetrachloride plant in the United States that employed the carbon disulfide route was permanently shut down. Consumption of carbon disulfide in mbber, agriculture, mining, and specialty industrial appHcations is anticipated to remain close to 1991 levels for the next several years.  [c.32]

Our concern here is mainly with the chemical interaction between the ocean and atmosphere through the exchange of gases and particulates. Through carbonate chemistry the deep ocean is a major reservoir in the global carbon cycle, and so can act as a long-term buffer to atmospheric COj. The surface ocean can act as either a source or sink for atmospheric carbon, with biological processes tending to amplify the latter. Biological productivity, mostly of planktonic life-forms, plays a major role in a number of other chemical interactions between ocean and atmosphere. Various gases that are direct or indirect products of marine biological activity act as greenhouse gases once released into the atmosphere. These include NjO, CH4, CO and CH3CI. This last one is also a natural source of chlorine, the element of most concern in the destruction of the ozone layer in the stratosphere.  [c.13]

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]

As you know, most countries are phasing out some refrigerants to lessen damage to the ozone layer. The chemicals being phased out are chlorofluorocarbons (CFCs) and hydrochlorofiuorocarbons (HCFCs). Replacements are hydrofluorocarbons (HFCs) and certain blends. The DuPont website gives a table of recommended replacement refrigerants for various applications. For each application DuPont lists the previously used refrigerant being phased out and the recommended new refrigerant for two cases "Retrofit or "New System. This table of refrigerants is in Chapter 11, "Refrigeration.  [c.395]

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]

Halocarbons have the further advantage of reducing the viscosity of the reaction mixture and, where used as the main blowing agent instead of the carbon dioxide produced by the isocyanate-water reaction, cheaper foams are obtained since less isocyanate is used. The reader should, however, note the comments made about the use of chlorofluoroearbons and their effect on the ozone layer made in Section 27.5.4.  [c.801]

OZONE A reactive form of oxygen the molecule of which contains 3 atoms of oxygen. In the ozone layer it protects the earth by filtering out ultra-violet rays. At ground level, as a constituent of photochemical smog, it is an imtant and can cause breathing difficulties.  [c.16]


See pages that mention the term Ozone layer : [c.526]    [c.502]    [c.503]    [c.349]    [c.26]    [c.387]    [c.38]    [c.39]   
13 Chemistry in the Marine Environment (2000) -- [ c.13 ]

Plastics materials (1999) -- [ c.798 ]

Chemistry of Organic Fluorine compounds II (1995) -- [ c.0 ]