Ozone layer oxides

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... 

The two scientists who first suggested (in 1974) that CFCs could deplete the ozone layer, F. Sherwood Rowland (1927-) and Mario Molina (1943-), won the 1995 Nobel Prize in chemistry, along with Paul Crutzen (1933—), who first suggested that oxides of nitrogen in the atmosphere could catalyze the decomposition of ozone. 

The nitrogen oxides are common pollutants generated by internal combustion engines and power plants. They not only contribute to the respiratory distress caused by smog, but if they reach the stratosphere can also threaten the ozone layer that protects Earth from harmful radiation. 

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... 

Meanwhile, Crutzen had done experiments showing that ozone in the upper atmosphere can be destroyed easily by reactions with nitrogen oxides. This work demonstrated that the ozone layer is in a delicate balance that could be disturbed significantly by changes in atmospheric composition. In 1974, Molina and Rowland combined Crutzen s experimental work with their own theoretical analysis and published a prediction (hypothesis) that CFCs pose a serious threat to the ozone layer. 

Since nitrous oxide, NjO, is a designated "greenhouse" gas, and may contribute to depletion of the ozone layer, its removal from emissions to atmosphere is desirable [1]. However, there are several reports that NjO can be formed at low selectivity as an undesirable by-product of NO+CO conversions during the initial warm-up-from-cold periods in three-way-catalytic (TWC) converters or components thereof [1-3]. TWC s commonly contain Rhodium and Ceria and although N,0 dissociation over RhjO, has been extensively studied [4], the following are among mechanistic possibilities as yet... 

Colorless, reactive gas. Oxygen was not present in the initial atmosphere of the Earth, although at 50 % it is the most common element in the crust of the Earth (oxides, silicates, carbonates, etc.). The compound with hydrogen is remarkable. The hydrides of all other elements are unpleasant compounds, but H20 is the molecule of life. The 02 found in the air today, of which it makes up 20 %, was formed in the process of evolution by photosynthesis of algae, which then also allowed life on solid land. Oxidation with oxygen became and is still the dominant pathway of life forms for obtaining energy (respiration). Used in medicine in critical situations. Oxidations play a key role in chemistry (sulfuric acid, nitric acid, acetic acid, ethylene oxide, etc.). The ozone layer in space protects the Earth from cosmic UV radiation. Ozone (03) is used in the... 

UV-irradiated cells. Using cell-free cytosolic keratinocyte extracts, Simon and colleagues26 confirmed the role of membrane oxidation in NF-kB activation. Particularly important aspects of the experimental design employed by Simon and colleagues was the use of keratinocytes versus cells derived from a cervical cancer patient, and the use of biologically relevant UVB (290 to 320 nm) radiation versus UVC (200 to 290 nm) radiation, which is filtered out by the atmospheric ozone layer and does not reach the earth s surface. Overall, these data indicate that the activation of cytokine transcription, a step essential for the induction of immune suppression, can occur independently of UV-induced DNA damage and suggest that membrane lipid oxidation can serve as a UV photoreceptor. 

This report deals primarily with the origins and effects of ozone and other photochemical oxidants. It is limited, more or less, to the problem of urban pollution and to such closely related topics as natural background in the earth s boundary layer. No consideration is given to the stratospheric ozone layer and the effects produced by supersonic transport (sst) emission or halocarbons. 

The role of biomass in the natural carbon cycle is not well understood, and in the light of predictions of a future atmospheric energy balance crisis caused by carbon dioxide accumulation, in turn the result of an exponential increase in the consumption of carbon fuel, the apparent lack of concern by scientists and policy makers is most troubling. Yet there is no other single issue before us in energy supply which will require action long before the worst effects of excess production will be apparent. The only satisfactory model is the action taken by the R D community with respect to the SST in nitric oxide potential and chloro-halocarbon emissions, when it was realised that the stratospheric ozone layer was vulnerable to interference. Almost all other responses to pollution" have been after definitive effects have become apparent. 

Ozone is the fourth strongest oxidant known to man and is more effective at sterilizing water than chlorine. Ozone s reaction with NO is a natural phenomenon that takes place in the upper atmosphere that depletes the ozone layer and creates acid... 

Heikes, B M. Lee, D. Jacob, R. Talbot, J. Bradshaw, H. Singh, D. Blake, B. Anderson, H. Fuelberg, and A. M. Thompson, Ozone, Hydroperoxides, Oxides of Nitrogen, and Hydrocarbon Budgets in the Marine Boundary Layer over the South Atlantic, J. Geophys. Res., 101, 24221-24234 (1996). 

A few comments on nitrous oxide Nitrous oxide (NzO) is a gas produced mainly through natural sources. However, generally, motor vehicles and combustion processes contribute to its formation in urban areas. Unfortunately, it is involved adversely in the two global environmental problems it contributes to the greenhouse effect and penetrates into the stratosphere, destroying the ozone layer. 

Nevertheless, ozone is beneficial in at least three ways. It is an excellent disinfectant and is used increasingly to sterilize municipal water supplies (Section 14.7). It can also be used as a powerful oxidant in the chemical process industries. Finally, O3 is an important constituent of the ozone layer in the stratosphere. The ozone layer absorbs short-wavelength ultra-... 

Following the demonstration in 1970 by Paul Crutzen that nitrogen oxides destroy ozone catalytically, there has been much concern that the ozone layer could be depleted by introduction of excessive amounts of nitrogen oxides from supersonic commercial aircraft operating in the stratosphere ... 

An ozone-sensitized oxidative conversion of methane to methanol has been reported.54 A double-layered Sr on La203 then M0O3 on a silica catalyst bed exhibited significantly higher yields of formaldehyde from a methane-air mixture than did M0O3 on silica alone.55... 

Hydrolysis of bromodifluoromethyl tnphenylphosphonium bromide, yielding bromodifluoromethane and triphenylphosphine oxide, proceeds via difluorocar-bene rather than by the bromodifluoromethyl carbanion [46 (equation 46). Bromodifluoromethane is a candidate for the replacement of Halon 1301 (CFjBr), a fire extinguishant presumed to cause damage to the stratospheric ozone layer... 

Nitrogen oxide contributes, like the chlorofluorocarbons, to the destruction of the ozone layer ... 

Ozone molecules can also react with chlorine radicals to induce the chain reaction and generate oxygen molecules and chlorine oxide radicals. The reaction mechanism is very much the same as that for ozone layer depletion by CFC compounds ... 

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