Atmosphere ozone, stratospheric

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. 

In the upper atmosphere (the stratosphere), the situation is quite different. There the partial pressure of ozone goes through a maximum of about 10-5 atm at an altitude of 30 km. From 95% to 99% of sunlight in the ultraviolet region between 200 and 300 nm is absorbed by ozone in this region, commonly referred to as the "ozone layer." The mechanism by which this occurs can be represented by the following pair of equations ... 

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. 

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. 

Ozone in the atmosphere is a good example of photochemical reactions. Atmospheric ozone is not due to equilibrium. The production and decomposition of ozone are largely by photochemical process, and the concentration of ozone in the stratosphere is at steady state, controlled by the kinetics of photochemical production and decomposition. 

Abstract Heterogeneous chemical reactions at the surface of ice and other stratospheric aerosols are now appreciated to play a critical role in atmospheric ozone depletion. A brief summary of our theoretical work on the reaction of chlorine nitrate and hydrogen chloride on ice is given to highlight the characteristics of such heterogeneous mechanisms and to emphasize the special challenges involved in the realistic theoretical treatment of such reactions. 

The discovery of the Ozone Hole in the Antarctic stratosphere has led to the realization that previously unsuspected heterogeneous chemical reactions occuring on the surface of ice and other stratospheric cloud particles play a critical role in atmospheric ozone depletion — not only in the Antarctic stratosphere,... 

The stratosphere is often referred to as the ozone layer, because of the relatively high concentrations produced by photochemical reactions in this region of the atmosphere. Ozone, derived from the Greek word meaning to smell, was first discovered by Schonbein in 1839. It has a rather pungent smell, which is sometimes noticeable around copy machines and laser printers that use discharge processes. 

A number of studies have measured the isotopic distribution in atmospheric ozone. There are three naturally occurring isotopes of oxygen, lftO, l70, and lxO, which might initially be expected to be represented statistically in atmospheric ozone. However, both stratospheric and tropospheric ozone have been measured to be enriched in the heavier isotopes over what one would expect statistically (e.g., see Mauersberger, 1981 Mauersberger et al., 1993 Krankowsky et al., 1995). A variety of explanations of this fractionation have been put forth, including nuclear symmetry restrictions on the 02 + O reaction that forms 03 (Hellene, 1996), the preferential dissociation of heavy ozone to form vibrationally excited 02 (u > 26) that then... 

Atmospheric ozone constitutes 0.64 10 6 of the atmospheric mass and belongs to the class of optically active gases. It absorbs UV solar radiation in the range 200 nm 300 nm, strongly affecting thereby the thermal regime of the stratosphere. Moreover,... 

These include toxicity, flammability, explosivity, stratospheric ozone depletion, atmospheric ozone production and global warming potential.[27] Bearing all these criteria in mind, the alternative solvents mentioned above provide an excellent range of properties with considerable potential. 

The concerns for changes in atmospheric ozone can be divided into two major categories changes in total column of ozone, and changes in the concentrations at particular altitudes. The penetration of ultraviolet radiation to the surface of the earth is determined almost entirely by the total amount of ozone in the atmospheric column, with very litde dependence on the altitude distribution of this ozone. However, if the prime concern is with processes such as the conversion of ultraviolet energy into heat after absorption by ozone (i.e. with the temperature structure of the stratosphere), then a redistribution of ozone to different altitudes is extremely important. 

Although it is an injurious pollutant in the lower atmosphere, ozone is an essential protective agent in the stratosphere. It is formed by photochemical dissociation of oxygen,... 

This section is mostly concerned with the presence of phosgene in the atmosphere, its formation and removal in both the troposphere (lower atmosphere) and stratosphere (upper atmosphere) and its possible effects on that part of the stratosphere known as the ozone layer. 

Since ROS are formed from the absorption of UVR by DOM and its subsequent photochemical decay, any changes in the atmosphere such as tropospheric warming or stratospheric ozone depletion should affect steady state concentrations of ROS in the water column. Initial studies with H2O2 suggest that the formation of an ozone hole will increase production rates by 20-50%. Changes in atmospheric ozone levels are also expected to affect production rates of other... 

Influence of stratospheric aerosol on total amount of atmospheric ozone... 

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