Ozone, atmospheric

Ozone (03) is a reactive oxidant gas produced naturally in trace amounts in the Earth s atmosphere. Ozone was discovered by C. F. Schonbein in the middle of the nineteenth 

FIGURE 2.6 Stratospheric ozone profile over Northern Hemisphere midlatitude (35CN) in September 1996 as measured by satellite with the Jet Propulsion Laboratory FTIR (Fourier transform infrared) spectrometer. Note that molecular concentration and mixing ratio peak at different altitudes. 

The Dobson Unit Imagine that all the ozone in a vertical column of air reaching from the Earth s surface to the top of the atmosphere were concentrated in a single layer of pure 03 at the surface of the Earth, at 273 K and 1.013 x 105 Pa. The thickness of that layer, measured in hundredths of a millimeter, is the column abundance of 03 expressed in Dobson units (DU). The unit is named after G. M. B. Dobson, who, in 1923, produced the first ozone spectrometer, the standard instrument used to measure ozone from the ground. The Dobson spectrometer measures the intensity of solar UV radiation at four wavelengths, two of which are absorbed by ozone and two of which arc not. 

One DU is equivalent to 2.69 x 1016 molecules 03 cm-2. A normal value of Oa column abundance over the globe is about 300 DU, corresponding to a layer of pure O3 at the surface only 3 mm thick. 

If the ozone concentration as a function of altitude is o5(z) (molecules cm-3), the 03 column burden is 

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Lowi, A. and W.P.L. Carter (1990), A method lor evaluating the atmosphere ozone impact of actual vehicle emissions . SAE paper No. 90-0710, International congress and exposition, Detroit, MI. 

Production of hydrogen fluoride from reaction of Cap2 with sulfuric acid is the largest user of fluorspar and accounts for approximately 60—65% of total U.S. consumption. The principal uses of hydrogen fluoride are ia the manufacture of aluminum fluoride and synthetic cryoHte for the Hall aluminum process and fluoropolymers and chlorofluorocarbons that are used as refrigerants, solvents, aerosols (qv), and ia plastics. Because of the concern that chlorofluorocarbons cause upper atmosphere ozone depletion, these compounds are being replaced by hydrochlorofluorocarbons and hydrofluorocarbons. 

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. 

Environmental Impact of Ambient Ozone. Ozone can be toxic to plants, animals, and fish. The lethal dose, LD q, for albino mice is 3.8 ppmv for a 4-h exposure (156) the 96-h LC q for striped bass, channel catfish, and rainbow trout is 80, 30, and 9.3 ppb, respectively. Small, natural, and anthropogenic atmospheric ozone concentrations can increase the weathering and aging of materials such as plastics, paint, textiles, and mbber. For example, mbber is degraded by reaction of ozone with carbon—carbon double bonds of the mbber polymer, requiring the addition of aromatic amines as ozone scavengers (see Antioxidants Antiozonants). An ozone decomposing polymer (noXon) has been developed that destroys ozone in air or water (157). 

Polyisobutylene has the chemical properties of a saturated hydrocarbon. The unsaturated end groups undergo reactions typical of a hindered olefin and are used, particularly in the case of low mol wt materials, as a route to modification eg, the introduction of amine groups to produce dispersants for lubricating oils. The in-chain unsaturation in butyl mbber is attacked by atmospheric ozone, and unless protected can lead to cracking of strained vulcanizates. Oxidative degradation, which leads to chain cleavage, is slow, and the polymers are protected by antioxidants (75). 

The horizontal dispersion of a plume has been modeled by the use of expanding cells well mixed vertically, with the chemistry calculated for each cell (31). The resulting simulation of transformation of NO to NO2 in a power plant plume by infusion of atmospheric ozone is a peaked distribution of NO2 that resembles a plume of the primary pollutants, SO2 and NO. The ozone distribution shows depletion across the plume, with maximum depletion in the center at 20 min travel time from the source, but relatively uniform ozone concentrations back to initial levels at travel distances 1 h from the source. 

The hazard identification step is perhaps the most important, because any hazard not identified will not be considered in the decision process. For example, the impact of chlorofluorocarbons on atmospheric ozone was unknown for much of the period of their use, and this potential hazard was not considered until recent years. 

In the atmosphere, ozone is attacked by chlorine atoms primarily introduced via polutants. The destruction of ozone is self-sustaining via these reactions ... 

The documentation of regional level terrestrial consequences of acid deposition is complicated. For example, forested ecosystems m eastern North America can he influenced by other factors such as high atmospheric ozone concentrations, drought, insect outbreaks and disease, sometimes from non-native sources. However there is a general consensus on some impacts of acidic depositon on both soils and forests m sensitive regions. 

In recent years, a minor component of the atmosphere, ozone, has received a great deal of attention. Ozone, molecular formula O3, is a pale blue gas with a characteristic odor that can be detected after lightning activity, in the vicinity of electric motors, or near a subway train. 

Depending on its location in the atmosphere, ozone can be a villain or a beleaguered hero. In the lower atmosphere (the tropo-... 

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. 

Oxidative catalytic converters are used to reduce CO and HCs originating from imperfect combustion in engines. At certain temperatures, these converters may also oxidize NO to NO2. Original equipment manufacturer (OEM) particle filters (PFs) employ NO2 to oxidize trapped soot at lower temperatures. However, the excess NO2 may escape from the system as tailpipe emissions. NO2 is very toxic to humans, and it also has impacts on atmospheric ozone-forming chemistry. Alvaraz et al. have stated that the primary NO2 emissions of modern diesel cars are increasing [76]. 

The story of research into the depletion of atmospheric ozone is just one example of how scientific understanding and theories develop. The fundamental theories and laws of chemistry that we present In this text all went through similar intense scrutiny and study. 

The results of the study reported here show clearly that, upon release into the atmosphere, N,N-dlmethylhydrazlne (UDMH) can be rapidly converted to N-nitrosodimethylamine by its reaction with atmospheric ozone. A similar conclusion can be reached concerning nitrosamine formation from other unsymmetrically disubstituted hydrazines ... 

In the lower layers of the atmosphere, ozone occurs only in trace quantities. Some ozone, however, is also created in the lower atmosphere by lightning, during electric storms, accounting for the "smell of rain" that... 

Atmospheric ozone has also been reported as causing fading of certain dyes in some countries [425,426] diallyl phthalate (10.182) used as a carrier in the dyeing of cellulose triacetate fibres, is said to be an effective ozone inhibitor [427]. Nylon, especially when dyed with certain amino-substituted anthraquinone blue acid dyes, can also be susceptible to ozone fading [428,429]. Selection of ozone-resistant dyes is obviously the best counteractive measure, although hindered phenols (10.161) and hindered amines (10.162) are said to provide some protection. 

Antiozonant additives are employed with unsaturated rubbers such as natural rubber, nitrile rubber, styrene-butadiene rubber, etc., to minimise the atmospheric ozone degradation reaction. Common antiozonant types include the parapheny-lene diamines such as N-(l,3-dimethylbutyl)-AT-phenyl-p-phenylene diamine (6PPD) and N-isopropyl-N7 phenyl-p-phenylene diamine (IPPD). Both these antioxidants can be identified and quantified using GC- or LC-based techniques. 

A dulling of the surface of vulcanised rubber articles considered to result from the action of atmospheric ozone, particularly in conditions of high humidity. It is quite different from blooming. 

In the present-day atmosphere ozone forms into layers and this was first explained by Chapman who proposed a photolysis mechanism for ozone formation. Chapman s mechanism is a simple steady-state production of ozone and led to the concept of odd oxygen. The odd-oxygen reaction scheme is shown in Table 7.4. 

Hanst, P.L., Stephens, E.R., Scott, W.E., Doerr, R.C. (1958) Atmospheric Ozone-Olefin Reactions. Franklin Institute, Philadelphia, Pa. 

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. 

Halon - As employed in the fire protection industry, a gaseous fire suppression agent. Halon is an acronym for halogenated hydrocarbons, commonly bromotrifluoromethane (Halon 1301) and bromochlorodifluoro-methane (Halon 1211). Considered obsolete for fire protection purposes due to a possible environmental impact to the Earth s atmospheric ozone layer and beginning to be phased out or eliminated. 

Fare TL et al (2003) Effects of atmospheric ozone on microarray data quality. Anal Chem... 

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