Ozone Depletion

11 Key excerpts on "Ozone Depletion"

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  Economic Analyses at EPA

  Assessing Regulatory Impact

  • Richard D. Morgenstern(Author)
  • 2014(Publication Date)
  • Routledge

    (Publisher)

  CFCs and Halons are nearly inert: they do not react readily with other compounds but persist in the environment on release. James Lovelock, an independent British scientist, noted in 1969 that this feature made CFCs potentially valuable as a chemical tracer of atmospheric motions, since virtually all of the CFCs produced to date remained in the lower atmosphere (Lovelock and others 1973). Not until the early 1970s did scientists determine the eventual fate of CFCs released to the environment: on drifting up to the stratosphere (the region of the atmosphere from about eleven to fifty kilometers above the earth’s surface), CFCs are dissociated by the intense solar ultraviolet (UV) radiation of that region. Through a chain of chemical reactions, the chlorine so released transforms ozone, a relatively unstable molecule of three oxygen atoms, into stable molecular oxygen, which contains only two atoms. Although ozone is in turn produced by photodissociation of molecular oxygen, the chlorine destroys ozone faster than it is produced and consequently the concentration of ozone in the stratosphere declines.

  Depletion of stratospheric ozone could have a wide range of consequences. Perhaps most important is the effect on UV radiation. Ozone is the primary atmospheric constituent that absorbs UV radiation, and most atmospheric ozone is concentrated in the stratosphere. Reduction in stratospheric ozone concentrations is likely to increase the quantity of solar UV radiation reaching the earth’s surface. Increases in UV radiation at the earth’s surface are expected to lead to increases in human skin cancers; increases in cataracts; possible reductions in immune function in humans and other animals; damage to terrestrial crops and other plants and to marine life, particularly plankton and fish larvae; and increased weathering of plastics. In addition, by reducing heat input to the stratosphere associated with UV absorption, Ozone Depletion may alter the heat balance of the atmosphere and so affect atmospheric circulation and global climate.

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  Comprehensive Study on Problems arising from Exploitation of Natural Resources, A

  • (Author)
  • 2014(Publication Date)
  • University Publications

    (Publisher)

  Another factor which may aggravate Ozone Depletion is the draw-down of nitrogen oxides from above the stratosphere due to changing wind patterns. History of the research The basic physical and chemical processes that lead to the formation of an ozone layer in the Earth's stratosphere were discovered by Sydney Chapman in 1930. These are discussed in Ozone-oxygen cycle — briefly, short-wavelength UV radiation splits an oxygen (O 2 ) molecule into two oxygen (O) atoms, which then combine with other oxygen molecules to form ozone. Ozone is removed when an oxygen atom and an ozone molecule recombine to form two oxygen molecules, i.e. O + O 3 → 2O 2 . In the 1950s, David Bates and Marcel Nicolet presented evidence that various free radicals, in particular hydroxyl (OH) and nitric oxide (NO), could catalyze this recombination reaction, reducing the overall amount of ozone. These free radicals were known to be present in the stratosphere, and so were regarded as part of the natural balance – it was ________________________ WORLD TECHNOLOGIES ________________________ estimated that in their absence, the ozone layer would be about twice as thick as it currently is. In 1970 Prof. Paul Crutzen pointed out that emissions of nitrous oxide (N 2 O), a stable, long-lived gas produced by soil bacteria, from the Earth's surface could affect the amount of nitric oxide (NO) in the stratosphere. Crutzen showed that nitrous oxide lives long enough to reach the stratosphere, where it is converted into NO. Crutzen then noted that increasing use of fertilizers might have led to an increase in nitrous oxide emissions over the natural background, which would in turn result in an increase in the amount of NO in the stratosphere. Thus human activity could have an impact on the stratospheric ozone layer. In the following year, Crutzen and (independently) Harold Johnston suggested that NO emissions from supersonic aircraft, which fly in the lower stratosphere, could also deplete the ozone layer.

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  The Dirty Dozen

  Toxic Chemicals and the Earth's Future

  • Bruce E. Johansen(Author)
  • 2003(Publication Date)
  • Praeger

    (Publisher)

  Some scientists sus- pected variability in the sun’s radiational output, and others sus- pected changes in atmospheric circulation. A growing minority began to suspect CFCs. These chemicals were not proven suspects when, in 1987, a majority of the world’s national governments signed the Montreal Protocol to eliminate CFCs. Definite proof of CFCs’ role in Ozone Depletion arrived shortly thereafter. J. G. Anderson, W. H. Brune, and M. H. Profitt (1989) implicated the chemistry of chlorine and explained the chain of chemical reactions (later broadened to bromides as a bit player)— the “smoking gun”—that explained why Ozone Depletion was so sharp and why it was limited to specific geographic areas at a spe- cific time of the year. The temperature of the stratosphere later came to be understood as a key ingredient in the mix—the colder the stratosphere, the more active the chlorine chemistry that devours ozone. By the year 2000, according to Maureen Christie (2001), Ozone Depletion was “significantly affecting ozone levels throughout the Southern Hemisphere” (86). When the Montreal Protocol was signed, the best science available was indicating that without remedial action the ozone destruction CFCs, Global Warming, and Ozone Depletion 81 rate would increase roughly 8 to 17 percent per year (a figure cal- culated for the early 1990s); by about 1992, it was projected that anthropogenic ozone destruction would rise to thirty-six times the natural rate (Crutzen 2001, 7). Matthew Stein, writing in When Technology Fails, describes how chlorine atoms come to destroy stratospheric ozone: CFCs are normally very stable, lasting 50 to 100 years before finally break- ing down. CFCs are lighter than air and slowly migrate into the upper at- mosphere, where high-energy rays from the sun blow them apart, liberating a chlorine atom into the ozone layer.

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  Environmental Policy and Public Health

  Air Pollution, Global Climate Change, and Wilderness

  • William N. Rom(Author)
  • 2011(Publication Date)
  • Jossey-Bass

    (Publisher)

  Chapter 9 Chlorofluorocarbons and the Development of the Ozone Hole Learning Objectives To understand what CFCs are and how they have contributed to destruction of the ozone layer in Antarctica To become knowledgeable about the ozone layer and how it is being depleted To become familiar with the Montreal Protocol and to discuss its effectiveness To understand the connections among the ozone layer, UV radiation, and biological health Chlorofluorocarbons (CFCs), along with other chlorine- and bromine-containing compounds, have been implicated in the accelerated depletion of ozone in the Earth's stratosphere. CFCs were developed in the early 1930s and are used in a variety of industrial, commercial, and household applications Production and use of chlorofluorocarbons experienced nearly uninterrupted growth as demand for products requiring their use continued to rise. It wasn't until the early 1970s that the link between CFCs and Ozone Depletion was made. Molina and Rowland published in Nature in 1974 that stratospheric ozone could be depleted as a consequence of the release of chlorofluorocarbons to the environment. 1 Observations of the ozone layer itself showed that depletion was indeed occurring; the most dramatic loss was discovered over Antarctica by the British Antarctic Survey in 1984. Ozone Depletion epitomizes the global environmental problems humans face: it is an unintended consequence of human activity. The way it was solved is a success story contributed to by many, including scientists, technologists, economic and legal experts, environmentalists, and policymakers. 2 Chlorofluorocarbons In the 1930s, Thomas Midgley 3 invented CFCs during a search for nontoxic substances that could be used as coolants in home refrigerators. Because of their chemical inertness and stability, the CFCs were considered to be “miracle” compounds. These substances are nontoxic, nonflammable, and nonreactive with other chemical compounds

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  Technology Transfer for the Ozone Layer

  Lessons for Climate Change

  • Stephen O. Andersen, K. Madhava Sarma, Kristen N. Taddonio(Authors)
  • 2012(Publication Date)
  • Routledge

    (Publisher)

  Chubachi reported the annual variation of total ozone and that the smallest value of total ozone since 1966 was observed in September to October 1982, when readings showed ozone levels of under 250 Dobson units. 13 In May 1985 Joseph S. Farman, B. G. Gardiner and J. D. Shanklin of the British Antarctic Survey published in Nature 14 their findings confirming that ozone levels above Antarctica had been significantly depleted every Antarctic spring since at least 1981. Their paper attributed the Ozone Depletion to CFCs, yet scientists would not be confident in this conclusion for several more years. The phenomenon of Ozone Depletion over Antarctica became known as the ‘ozone hole’. Environmental scientists describe bleak future with Ozone Depletion Scientists’ reports that Ozone Depletion was sure to increase the incidence of skin cancer attracted significant attention in the US and other countries. However, they also described other impacts with far greater global consequences, particularly the potential reduction in global food supply and proliferation of diseases caused by the effects of ultraviolet radiation on the human immune system. 15 Scientists testified that the potential of ultraviolet radiation to damage crops and plants was indisputable. 16 T HE I NCREASING U SE OF O ZONE -D EPLETING S UBSTANCES Chemical emissions responsible for ozone layer depletion came from various sources. In about 1900 methyl bromide became the first ODS to be commercialized. 17 Carbon tetrachloride was the second. Chlorofluorocarbons (CFCs) are the most familiar ozone-depleting substances, but the first CFCs (CFC-11 and CFC-12) were not commercialized until the 1930s. Halon-1211 and 1301 were commercialized in the 1940s

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  Exploring Environmental Issues

  An Integrated Approach

  • David D. Kemp(Author)
  • 2004(Publication Date)
  • Routledge

    (Publisher)

  The popularity of CFCs and halons stemmed from their stability and low toxicity, which meant, for example, that they could be used as propellants in the inhalers required by those suffering respiratory problems without changing the efficacy of the medication or causing harm to the user. Being inert, they were also ideal solvents for cleaning delicate electronic components such as computer chips. However, the very properties that made CFCs and halons so useful ultimately allowed them to become the major contributors to Ozone Depletion. Their stability allowed them to accumulate in the environment relatively unchanged. With time they gradually diffused into the upper atmosphere, where they

  Figure 11.3 CFC production and the concentration of ozone-depleting substances (ODS) in the atmosphereSource: based on data in UNEP (2002) and World Resources Institute, Earthtrends. Viewed at http://www.earthtrends.wri.org/ (accessed 4 April 2003).

  encountered conditions under which they were no longer inert, and broke down to release by-products capable of depleting the stratospheric ozone layer. Their capacity to destroy ozone varies and is represented by their Ozone Depletion potential (ODP). CFC-11, with an ODP of 1, is the standard against which all other ozone-destroying chemicals are measured. The ability of Halon-1301 (ODP 12) to destroy ozone, for example, is twelve times greater than that of CFC-11 (Table 11.2 ).

  In 1974 Mario Molina and Sherwood Rowland, atmospheric scientists at the University of California, Irvine, using the results of their investigations into the photochemistry of the stratosphere, were the first to explain the processes by which the depletion was accomplished. They recognized that the high levels of ultraviolet radiation in the upper atmosphere caused the photochemical degradation of the normally inert CFCs, leading to the release of chlorine. Catalytic chain reactions initiated by the free chlorine then began the process of depleting the ozone layer (Figure 11.2 b). The importance of the chlorine catalytic chain lies in its efficiency; it is six times more efficient catalytically than the nitric oxide cycle, for example. The chain is broken only when the chlorine or chlorine monoxide molecules gain a hydrogen atom from one of the hydrogen oxides, or from a hydrocarbon such as methane, and is converted into hydrochloric acid, which diffuses into the lower atmosphere, eventually to be washed out by rain. The combination of chlorine monoxide with nitrogen dioxide to form chlorine nitrate also breaks the chain (Turco 1997). Conclusions similar to those of Molina and Rowland were reached independently at about the same time by other researchers (Crutzen 1974; Cicerone et al. 1974; Wofsy et al.

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  The Ozone Layer

  Proceedings of the Meeting of Experts Designated by Governments, Intergovernmental and Nongovernmental Organizations on the Ozone Layer, Organized by the United Nations Environment Programme in Washington, DC, 1-9 March 1977

  • Asit K. Biswas(Author)
  • 2013(Publication Date)
  • Pergamon

    (Publisher)

  PAPER 12 Stratospheric Ozone Depletion - An Environmental Impact Assessment Presented by ICSU/SCOPE INTRODUCTION The Problem The stratospheric ozone layer is important for two reasons: it shields the surface of the earth from the ultra-violet (UV) rays of the sun; and it is an integral part of the world atmosphere system. A widely discussed topic at the present time is the degree of fragility of the ozone layer. Mankind is becoming capable of environmental disruption on a global scale; trace substances are being introduced into the atmosphere in ever increasing amounts and some of these materials are reaching the stratosphere where they may upset the natural balance of the ozone layer. The resulting perturbations are not yet detectable but a slow depletion in ozone concentrations is predicted in future years if the chemical releases to the atmosphere continue in increasingly large amounts. Because of the great natural variability in stratospheric ozone from place to place and from year to year, it will be difficult to determine the extent of ozone deple-tion in the years ahead. In fact, one of the special aspects of the ozone problem is that if mankind waits until there are experimental data confirming a downward trend in ozone concentrations, it will already be too late to prevent an extended period of Ozone Depletion. In this paper, an environmental impact assessment is given of the problem of stratospheric Ozone Depletion. An Historical Perspective** The stratospheric ozone layer has been studied for many decades. As early as 1880, Hartley suggested that atmospheric ozone was absorbing UV sunlight. However, the first accurate ground-based measurements of total ozone were not made until 1920 when Fabry and Buisson determined the amount of ozone over Marseilles, during a ^Prepared for ICSU/SCOPE by the Scope Monitoring and Assessment Research Centre, Chelsea College, University of London (15 January 1977).

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  Discerning Experts

  The Practices of Scientific Assessment for Environmental Policy

  • Michael Oppenheimer, Naomi Oreskes, Dale Jamieson, Keynyn Brysse, Jessica O’Reilly, Matthew Shindell, Milena Wazeck, Jessica O'Reilly(Authors)
  • 2019(Publication Date)
  • University of Chicago Press

    (Publisher)

  Indeed, chapter 1 of part 2 is called “The Chlorofluorocarbon Problem.” While allowing that more work was needed, particularly more observations of the stratosphere, it emphasized the general agreement in the scientific community that should CFC emissions continue, Ozone Depletion would occur. There was also general agreement as to the range of expected depletion—5%–20%—although the report did point out that consensus did not equate to truth, and “the fact that a number of independent workers who used these same assumptions calculate eventual Ozone Depletion in the same range . .

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  Protecting the Ozone Layer

  The United Nations History

  • Stephen O Andersen, K Madhava Sarma, Stephen O. Andersen, K.Madhava Sarma(Authors)
  • 2012(Publication Date)
  • Routledge

    (Publisher)

  ‘The surface-induced, PSC-induced chemical reactions which cause the Ozone Depletion in Antarctica and also occur in the Arctic, represent additional ozone-depleting processes that were not included in the stratospheric ozone assessment models used to guide the Montreal Protocol. Recent laboratory studies suggest that similar reactions involving chlorine compounds may occur on sulfate particles present at lower latitudes, which could be particularly important immediately after a volcanic eruption. Hence, future global ozone layer depletions could well be larger than originally predicted.’

  Complete elimination of ODS emissions needed to save the ozone layer The Scientific Assessment Panel concluded:

  ‘To return the Antarctic ozone layer to levels of the pre-1970s, and hence to avoid the possible ozone dilution effect that the Antarctic ozone hole could have at other latitudes, one of a limited number of approaches to reduce the atmospheric abundance of chlorine and bromine is a complete elimination of emissions of all fully halogenated CFCs, halons, carbon tetrachloride, and methyl chloroform, as well as careful considerations of the HCFC substitutes. Otherwise, the Antarctic ozone hole is expected to recur seasonally, provided the present meteorological conditions continue.’

  First Report of the Environmental Effects Assessment Panel

  The first report of the Environmental Effects Panel published in November 1989 concluded that exposure to increased ultraviolet radiation can cause suppression of the body’s immune system, which might lead to an increase in the occurrence or severity of infectious diseases such as herpes, leishmaniasis and malaria, and a possible decrease in the effectiveness of vaccination programmes. It also found that enhanced levels of ultraviolet radiation can lead to increased damage to the eyes, especially the cataracts, the incidence of which was expected to increase by 0.6 per cent per 1 per cent total column Ozone Depletion. Therefore, each 1 per cent total column Ozone Depletion was expected to lead to a worldwide increase of 100,000 blind persons due to ultraviolet-radiation-induced cataracts.

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  Integration of Public Health with Adaptation to Climate Change: Lessons Learned and New Directions

  • Kristie L Ebi, Joel B Smith, Ian Burton(Authors)
  • 2005(Publication Date)
  • CRC Press

    (Publisher)

  Stratospheric ozone 221 Convention signed, on the basis that it was theoretically that Cl� Cs could cause depletion of stratospheric ozone. Indeed, this action had been taken two months before the first concrete evidence of changes in the ozone layer was released! In 1 9 8 7, 36 nations signed the Montreal Protocol on Substances that Deplete the Ozone Layer to limit the production of ozone-depleti ng chemicals, with an aim to halve Tab le 1 1 . 1 Atmospheric lifet ime (years) and ozone-depleti ng potential of selected halocarbons Comp()/ md Relatiue ozone-depleting potential a CFC-l l CFC-2 CFC-1 1 3 CFC-1 14 CFC-l ] 5 HCFC 22 HCFC-123 HFC-1 34a Notes 1 . 0 J) 0.8 1 . 0 0.6 0.OS5 0.0 1 6 o a From the Montreal Protocol. b From Ref. 21. 501J 400 300 160 1 40 1 00 �() 1 978 1 982 1 916 19 90 19 94 50 108 88 1 80 .185 1 3 1 .4 1 8 (years) b Figure 1 1 . 6a Accumulation of ;1tmospheric CFCs ;1nd destruction of stratospheric ozone. Source: Data fr0111 Ref. 22 222 Integration oj public health with to climate 320 31 0 � 300 (J) 290 c o o 280 270 260 Mean Summer Ozone and Estimated UV Index Lauder, New Zealand B 1 2.0 l l 1 1 .5 i : : : � f', � i O.O � J ' 0' 1 I 9 . 5 J r I I i I I I T I I I ! I I I II I I Summer Year (December-February) Figure 1 1 .6b The upper p:mel shows average summertime ozone measured at Lander 170E, 3 70 m alt), :cntral Otago, New Zealand. Here the sum mer is defined as December through Fehruary. The lower panel shows the corresponding noontime UV index for clear skies. A clear decrease in ozone and increase in UV, which is larger than the year to year variability, can be seen over the period 1 980 to 2000. There is a suggestion of a recovery since then, but the time is too to detect it unambig uo usly over the natural variability. from RiciJard Iv1cKem:ie, personal communication 2000 19] . The Montn:�11 Protocol amende d in 1 990 and > 9 92 to Zlccelerate the phaseout schedules for halons, and hydroc hlorof luorocarbons (HCFCs).

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  Applied Atomic Collision Physics

  Atmospheric Physics and Chemistry

  • H.S.W. Massey(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  14. This redistribution of the 0 3 height profile might have climatic consequences. Hampson (1974) pointed out that a nuclear war would seriously alter the NO x content of the atmosphere and thus produce a global doomsday scenario. With large inputs, the NO x catalytic chain dominates stratospheric chemistry and 0 3 destruction occurs at all altitudes. Depending on the yield of NO x in the explosion, a nuclear war involving about 10,000 megaton equivalents has been estimated by Duewer et al. (1978a) to cause 0 3 deple-tions of 30-60%. XII. Consequences of 0 3 Depletion Although it is not the function of this chapter to discuss the effects of atmospheric changes, I suspect that a reader who has persevered this far might feel frustrated if no mention is made of the likely consequences of 0 3 depletion. A brief summary will therefore be given, and the reader is referred to other reviews, such as the NAS (1979) report entitled Protection Against Depletion of Stratospheric Ozone by Chlorofluorocarbons, for more comprehensive information. There are two main effects of a decrease in stratospheric 0 3 . First, there will be an increase in the amount of UV radiation which penetrates to the surface. Second, decreased 0 3 means less heating in the stratosphere by solar UV absorption and subsequent chemistry. The most publicized effect of increasing the UV flux to the surface is the possibility of an increase in the incidence of skin cancer. There is a multiplica-tion factor of about 2 between the decrease in 0 3 and the increase in erythemal radiation—that part of the solar spectrum, near 300 nm, which causes sun-burn and which is implicated in skin cancer. 342 H. I. Schiff There is fairly convincing evidence connecting the cumulative dose of erythemal radiation with nonmelanoma skin cancer. This form of skin cancer is rarely fatal, but it can be disfiguring and does require medical treatment.

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