Ozone cycle

B. Nitric Oxide, Nitrogen Dioxide, and Ozone Cycles... 

Combine these three equations in appropriate numbers with cancellation of common species to show that the overall ozone cycle converts UV light into heat h V( i=i8o 34o nm) Heat... 

Theoretical interpretation of the experimental observations will help in determining the relative roles played by stratospheric injection, plant emission, background methane, and transport to surfaces in the natural portion of the tropospheric ozone cycle. 

FIGURE 14-1 The tropospheric ozone cycle. Reprinted with permission from Corn er al.. Photochemical oxidants Sources, sinks and strategies, J. Air Pbllut. Control Assoc. 25 16-18, 1975. 

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. 

Nitrous oxide is nontoxic—it used as the propellant in whipped-cream spray cans—and so might seem to be an unlikely pollutant. However, as noted earlier, it may contribute significantly to greenhouse warming. Furthermore, on diffusing to the stratosphere, N20 becomes involved in the ozone cycle (reactions 8.2, 8.3, and 8.6) following its conversion to nitric oxide (NO) ... 

Millan MM, Sanz MJ, Salvador R, Mantilla E (2002) Atmospheric dynamics and ozone cycles related to nitrogen deposition in the western Mediterranean. Environ Pollut 118 167-186... 

There are various approaches to parameterizing the process of formation and destruction of the ozone layer. The difficulty of deriving dynamic models of the ozone cycle in the atmosphere has to do with the participation in the cycle of more than 75 chemical reactions, a qualitative and quantitative description of which is impossible without deriving detailed models of the many minor gas components of the atmosphere. Nevertheless, there are empirical models of the ozone layer, which make it possible, under the present climatic situation, to obtain adequate spatial distributions of ozone. For instance, Bekoryukov and Fedorov (1987) derived a simple empirical model of total ozone content confirmed by observational data for the Southern Hemisphere ... 

Anthropogenic impacts on the oxygen and ozone cycles 4.5.3.1 Oxygen cycle and anthropogenic processes... 

Photodissociation is at the heart of photochemistry (Turro 1965, 1978 Calvert and Pitts 1966 Ben-Shaul, Haas, Kompa, and Levine 1981 von Btinau and Wolff 1987 Wayne 1988 Klessinger and Michl 1989). In many cases, the photofragments are radicals which rapidly undergo secondary and tertiary reactions. Photodissociation is the motor for many important chain reactions determining the complex chemistry in the atmosphere. The sun supplies sufficient UV radiation to keep the motor going (Okabe 1978). The ozone cycle,... 

As you learned earlier, chlorolluorocarbons (CFCs) are chemicals that interfere with the ozone cycle high up in the atmosphere. CFCs are nontoxic, nonflammable compounds that contain atoms of chlorine, carbon, and fluorine. These gases are human-made compounds that were released into the atmosphere primarily from refrigeration and aerosol devices. 

Q The oxygen molecule that forms when ozone photo-dissociates is available to start the ozone cycle anew. 

The concentration of CO (see Fig. 7), hydrocarbons and NO are higher in the air over the Northern Hemisphere than over the Southern Hemisphere, which leads to a higher tropospheric 03 formation rate in these areas. Considering the complexity of the problem and our insufficient knowledge of some chemical processes we are not able at present to draw a final conclusion on the tropospheric ozone cycle. It is to be stressed, however, that there are several arguments in the literature (besides Fishman and Crutzen (1978) see, e.g. Ripperton et ai. 1971) supporting the hypothesis that tropospheric air also acts as an O, source. 

This stratospheric temperature decrease can modify, among other things, the ozone cycle. 

Nitric oxide (NO) plays a central role in atmospheric chemistry, influencing both ozone cycling and the tropospheric oxidation capacity through reactions with hydroperoxy- and organic peroxy-radicals. When the NO concentration exceeds 40 pptv (pptv = parts per trillion by volume) it catalyzes the production of ozone (O3) ... 

Middleton N, Yiallouros P, Kleanthous S et al (2008) A 10-year time-series analysis of respiratory and cardiovascular morbidity in Nicosia, Cyprus the effect of short-term changes in air pollution and dust storms. Environ Health 7 39 Millan M, Salvador R, Mantilla E et al (1997) Photo-oxidant dynamics in the Mediterranean basin in summer results from European research projects. J Geophys Res 102 8811-8823 Millan MM, Sanz Ml, Salvador R et al (2002) Atmospheric dynamics and ozone cycles related to nitrogen deposition in the western Mediterranean. Environ Pollut 118 167-186 Mostafa AR, Hegazi AH, El-Gayar MS et al (2009) Source characterization and the environmental impact of urban street dusts from Egypt based on hydrocarbon distributions. Fuel 88 95-104... 

The first and third processes are photochemical they use a solar photon to initiate a chemical reaction. The second and fourth are exothermic chemical reactions. The net result of the four reactions is a cycle in which solar radiant energy is converted into thermal energy. The ozone cycle in the stratosphere is responsible for the rise in temperature that reaches its maximum at the stratopause (Figure 18.1). 

The reactions of the ozone cycle account for some, but not all, of the facts about the ozone layer. Many chemical reactions occur that involve substances other than oxygen. We must also consider the effects of turbulence and winds that mix up the stratosphere. A complicated picture results. The overall result of ozone formation and removal reactions, coupled with atmospheric turbulence and other factors, is to produce the upper-atmosphere ozone profile shown in FIGURE 18.4, with a maximum ozone concentration occurring at an altitude of about 25 km. This band of relatively high ozone concentration is referred to as the ozone layer or the ozone shield. ... 

Ozone Production In the Troposphere The Tropospheric Ozone Cycle and Ozone Distribution... 

Two other shields come from chemistry in gaseous air and liquid sea. The air shield is the ozone cycle, which comes from oxygen, so it wasn t around at the very beginning. It unfolded as photosynthesis began to release oxygen into the atmosphere about 2.5 billion years ago. 

Contrast the ozone cycle with the atmospheric cycles that predominate on other planets Venus has a sulfuric acid cycle from its interior sulfur dioxide volcanoes, while Mars has a peroxide cycle from solar radiation shearing the oxygens off carbon dioxide. The Martian atmosphere has a little water in it, and even a trace of ozone built from these oxygen atoms, but its reactions are uncontrolled and out of kilter, making dangerous peroxide H Oj molecules. Their chemical cycles are destructive, but ours is protective. 

The ozone cycle is connected to the oceans because when sunlight splits water vapor into hydrogen and oxygen, hydrogen exits into outer space and oxygen is left behind. For a brief moment, this can form ozone. Liquid water in contact with sunlit air makes a fleeting ozone umbrella. 

Collective cycles have emerged with very different types of molecules and reactions. The ozone cycle uses simple molecules. Some reactive circles use complicated molecules, like nine peptides, or RNA. Something similar for small molecules in vent... 

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