That Destroy Stratospheric Ozone

The Chapman mechanism for ozone formation and destruction is incomplete. There are compounds from natural sources—N O from agriculture, and OH from water, for example—that contribute to ozone s destruction. In an impoUuted stratosphere, a balance between formation and destruction is maintained. Nothing can be done to promote the formation of ozone in the stratosphere. Several pollutants, however, can very effectively promote the destruction of ozone. 

Ozone can be produced very easily in the troposphere. However, it is too reactive in the troposphere for any of it to reach the stratosphere. We do not have a way to produce ozone in the stratosphere. Several chemical compounds of human origin, however, can destroy the stratosphere s ozone. 

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Perfluorinated ethers and perfluorinated tertiary amines do not contribute to the formation of ground level ozone and are exempt from VOC regulations (32). The commercial compounds discussed above have an ozone depletion potential of zero because they do not contain either chlorine or bromine which take part in catalytic cycles that destroy stratospheric ozone (33). 

Stratospheric ozone depletion is one of the best-established phenomena arising from anthropogenic influence on the global environment. As chlorofluorocarbons and other chlorinated and brominated substances are emitted into the atmosphere, those that are not subject to attack in the troposphere may reach the stratosphere where UV radiation breaks the molecules apart, releasing their halogen atoms. These halogen atoms initiate catalytic cycles that destroy stratospheric ozone one chlorine atom can destroy as many as 100,000 ozone molecules before finally being removed from the stratosphere. 

Stratospheric O3 depletion, commonly known as the ozone hole, is caused by the release into the atmosphere of certain manmade substances that destroy the ozone (the good ozone) at high altitude. Because of the thinning of the ozone layer,... 

The NO produced will then destroy stratospheric ozone in a reaction that regenerates it ... 

For some pesticide compounds, such as dini-troaniline herbicides (Weber, 1990), phototransformation occurs primarily in the vapor phase, rather than in the dissolved or sorbed phases. Perhaps the most environmentally significant pesticide phototransformation in the atmosphere, however, is the photolysis of the fumigant methyl bromide, since the bromine radicals created by this reaction are 50 times more efficient than chlorine radicals in destroying stratospheric ozone (Jeffers and Wolfe, 1996). Detailed summaries of the rates and pathways of phototransformation of pesticides and other organic compounds in natural systems, and discussions of the physical and chemical factors that influence these reactions, have been presented elsewhere (e.g., Zepp et al, 1984 Mill and Mabey, 1985 Harris, 1990b). 

Unfortunately, these compounds were found to destroy stratospheric ozone.133 This is the layer that protects us from ultraviolet light. Without it, or with less of it, there will be more skin cancers and cataracts. The decline has been worldwide, but most significantly in the polar regions. The ozone hole in Antarctica was 25 million km2 in September 1998 (i.e., 2.5 times the area of Europe).134 Ozone levels at the North Pole have fallen 40% since 1982.135 A 15-year study shows an increase in the wavelengths that can damage DNA of 8% per decade at 40-de-grees north latitude, the latitude of Philadelphia, Pennsylvania and Madrid, Spain. 

Another group of compounds that can destroy stratospheric ozone are the nitrogen oxides, generally denoted as NO. (Examples of NO are NO, NO2, N2O, and N2O5.) These compounds come from the exhausts of high-altitude supersonic aircraft and from human and natural activities on Earth. Solar radiation decomposes a substantial amount of the other nitrogen oxides to nitric oxide (NO), which participates in the destruction of ozone as follows ... 

Raul Crutzen discovers that oxides of nitrogen (NOJ destroy stratospheric ozone ... 

Ever) year our planet is bombarded with enough energy from the Sun to destroy all life. Only the ozone in the stratosphere protects us from that onslaught. The ozone, though, is threatened by modern life styles. Chemicals used as coolants and propellants, such as chlorofluorocarbons (CFCs), and the nitrogen oxides in jet exhausts, have been found to create holes in Earth s protective ozone layer. Because they act as catalysts, even small amounts of these chemicals can cause large changes in the vast reaches of the stratosphere. 

Susan Solomon and James Anderson showed that CFCs produce chlorine atoms and chlorine oxide under the conditions of the ozone layer and identified the CFCs emanating from everyday objects, such as cans of hair spray, refrigerators, and air conditioners, as the primary culprits in the destruction of stratospheric ozone. The CFC molecules are not very polar, and so they do not dissolve in rain or the oceans. Instead, they rise to the stratosphere, where they are exposed to ultraviolet radiation from the Sun. They readily dissociate in the presence of this radiation and form chlorine atoms, which destroy ozone by various mechanisms, one of which is... 

C15-0094. NO is an atmospheric poiiutant that destroys ozone in the stratosphere. Here is the accepted O3 + NO NO2 + O2 (slow)... 

The term CFCs is a general abbreviation for ChloroFluoroCarbons. They have been extensively used since their discovery in the thirties, mainly as refrigerant, foam blowing agent, or solvent because of their unique properties (non toxic, non flammable, cheap). However, after the first warning of Rowland and Molina [1] in 1974 that CFCs could destroy the protective ozone layer, the world has moved rapidly towards a phase-out of CFCs. Because the destruction of stratospheric ozone would lead to an increase of harmful UV-B radiation reaching the earth s surface, the production and use of CFCs is prohibited (since January 1, 1995 in the European Union and since January 1, 1996 worldwide). 

The different greenhouse gases can have complicated interactions. Carbon dioxide may cool the stratosphere which slows the process that destroys ozone. Stratospheric cooling can also create high altitude clouds which interact with chlorofluorocarbons to destroy ozone. Methane may be produced or destroyed in the lower atmosphere at various rates, which depend on the pollutants that are present. Methane can also affect chemicals that control ozone formation. 

Chlorine atoms and other chlorine species formed by photodecomposition of carbon tetrachloride in the stratosphere can catalyze reactions that destroy ozone. As the manufacture of carbon tetrachloride for use in chlorofluorocarbons is phased out according to a recent international agreement (EPA 1987e), the impact of carbon tetrachloride on atmospheric ozone is likely to decrease. 

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