Ozone depletion, result

In the third section, we review recent developments in the field of atmospheric free radical observations so we can explore how effectively these experiments have tested our understanding of atmospheric structure. The fourth section summarizes this progress and then presents the latest predictions of global ozone depletion resulting from fluorocarbon release. Recent and important changes have been reported in this aspect of the problem. 

Fig. 1.3 Observed and calculated percentage ozone depletions resulting from the 1972 solar proton event The various calculated curves correspond to assumed values of parameters that were not well known...

Birks, J.W. Cmtzen, P.J. Roble, R.G., 2007 Frequent Ozone Depletion Resulting from Impacts of Asteroids and Comets , in Bobrowsky, P. Rickman, H. (Eds.) Comet/Asteroid Impacts and Human Society (Berlin Springer) 225-245, doi 10.1007/978-3-540-32711-0. 

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. 

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."... 

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. 

Depletion of siraiospherio ozone Ozone depletion projcoied lo result in 10,000 additional annual deaths not ranked liigher beoause of the unocrtainiics in future risk. 

This process does not lead to net ozone depletion because it is rapidly followed by reaction 2, which regenerates the ozone. Reactions 2 and 3 have, however, another important function, namely the absorption of solar energy as a result, the temperature increases with altitude, and this inverted temperature profile gives rise to the stratosphere (see Figure 1). In the lower layer, the troposphere, the temperature decreases with altitude and vertical mixing occurs on a relatively short time scale. In contrast, the stratosphere is very stable towards vertical mixing because of its inverted temperature profile. 

In order to estimate the extent of ozone depletion caused by a given release of CFCs, computer models of the atmosphere are employed. These models incorporate information on atmospheric motions and on the rates of over a hundred chemical and photochemical reactions. The results of measurements of the various trace species in the atmosphere are then used to test the models. Because of the complexity of atmospheric transport, the calculations were carried out initially with one-dimensional models, averaging the motions and the concentrations of chemical species over latitude and longitude, leaving only their dependency on altitude and time. More recently, two-dimensional models have been developed, in which the averaging is over longitude only. 

Certainly, photochemical air pollution is not merely a local problem. Indeed, spread of anthropogenic smog plumes away from urban centers results in regional scale oxidant problems, such as found in the NE United States and many southern States. Ozone production has also been connected with biomass burning in the tropics (79,80,81). Transport of large-scale tropospheric ozone plumes over large distances has been documented from satellite measurements of total atmospheric ozone (82,83,84), originally taken to study stratospheric ozone depletion. 

Although in this chapter we have focused on the potential effects of increased UV-B radiation on the Antarctic marine ecosystem, our results also have bearing on efforts to describe the effects of UV radiation on global marine productivity. However, here again, considerable uncertainties still remain in assessing the effects of ozone depletion on global production. Several authors have predicted a... 

The life cycle impact assessment (LCIA) is used to assess the results of the LCA and evaluate the impact on the environment in the various impact categories. These impact categories include, for example, human health, GWP, energy, water use, eutrophication, ozone depletion, aquatic toxicity, and land use (ISO, 2006b). LCA may focus on one or more impact categories. The results may be normalized, weighted, and aggregated in optional steps of the LCIA for comparison to political objectives, for example. In addition, sensitivity analyses are often conducted over the entire LCA to evaluate the variation in the results due to selected factors. 

Laturnus F, Svensson T, Wiencke C, Oberg G (2004) Ultraviolet radiation affects emission of ozone-depleting substances by marine macroalgae results from a laboratory incubation study. Environ Sci Technol 38 6605-6609... 

It is clear from the data presented in this chapter that the effects of control strategies developed for CFCs and halons are already measurable. Although loss of stratospheric ozone with accompanying increases in ultraviolet radiation in some locations have clearly occurred, the tropospheric concentrations of CFCs are not increasing nearly as fast as in the past. Indeed, the concentrations of CFC-11 and CFC-113 appear to have peaked and have started to decline. The equivalent effective stratospheric chlorine concentrations are predicted to have peaked about 1997 and to return to levels found around 1980 at about the year 2050 (World Meteorological Organization, 1995). The significance of the 1980 level is that these levels resulted in detectable Antarctic ozone depletion. 

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