Stratosphere pollution injection

Atom for atom, bromine is even more efficient at destroying ozone than is chlorine. There has therefore been much concern that releases of volatile bromine compounds such as methyl bromide may contribute disporpor-tionately to thinning of the stratospheric ozone layer. Whereas there is no longer any doubt over the role of human activity in stratospheric pollution by CFCs, which are exclusively anthropogenic, attempts to assess the importance of human activity in pollution by methyl bromide have been confused by large natural releases of CH3Br from oceans and forest fires. Besides, unlike the case of CFCs released into the environment, a major fraction of the methyl bromide injected into soils to kill pests is destroyed in the ground. 

Photochemical air pollution in the troposphere results from a complex interplay between sunlight and primary air pollutants emitted in ambient air that leads to the formation of ozone and other oxidizing and cye-irritaling agents. On the other hand, pollutants injected into the stratosphere by such human activities as supersonic transports (SST s) and release ofchlorofiuoro-methancs in air by their use as aerosol propellants and refrigerants may eventually reduce the protective layer of ozone from harsh solar ultraviolet radiation. Although the full impact of injected air pollutants in the stratosphere is not apparent at present, various model calculations show conclusively that the continuous future release of chlorofluoromethanes and NO (NO and N02) would result in substantial reduction of ozone in the stratosphere. 

As the residence time of aerosols in the stratosphere is 2 yr and in the troposphere 1 week, the Be/ Be ratio of the two air masses is distinctive. Tropospheric air shows the ratio of Be relative to Be of 1.8, whereas stratospheric air has a ratio of 0.13. It is therefore possible to distinguish stratospheric air injected into the troposphere by considering the ratio of Be/ Be. Of course, the stratospheric air will also be higher in Be than the tropospheric air. As stratospheric air will also contain ozone, the interest in this source has been strong to distinguish from pollution-based tropospheric ozone. 

This is a very broad conclusion, and additional measurements must be made. Some of this effort (which is current) should address the problem of other pollutants and condensation nuclei that accompany the nonurban oxidant. Interpretation of these measurements will increase the specificity of separating anthropogenic sources from natural background sources. Theoretical assessments of the existing observations will shed light on the relative roles played by stratospheric injection, plant emission, background methane, and diy deposition on surfaces in the natural portion of the tropospheric ozone cycle. 

Pollution in the stratosphere may induce the reduction of ozone without participation of sunlight in the case of NO injected directly into the stratosphere by SST s. while in the case of chlorofluoromethanes, their photodissociation by sunlight to produce Cl atoms is required for the reduction of ozone by a catalytic cycle involving Cl and CIO. The time scale required... 

Atmospheric pollution has become a worldwide concern. With the prospect of supersonic transports fiying in the stratosphere came initial questions as to how the water vapor ejected by the power plants of these planes would affect the stratosphere. This concern led to the consideration of the effects of injecting large amounts of any species on the ozone balance in the atmosphere. It then became evident that the major species that would affect the ozone balance were the oxides... 

FIGURE 4-1 Vertical structure of the atmosphere. Weather phenomena are confined almost entirely to the troposphere, as are most air pollutants, which are removed by various processes before they can mix into the stratosphere. Certain long-lived pollutants, however, such as the chlorofluorocarbons (CFCs), do mix into the stratosphere, and other pollutants can be injected physically to stratospheric altitudes by processes such as volcanic eruptions or nuclear explosions. Note that more than one term may refer to a given layer of the atmosphere (adapted from Introduction to Meteorology, by F. W. Cole. Copyright 1970, John Wiley Sons, Inc. Reprinted by permission of John Wiley Sons, Inc.). 

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