Ozone Action

Even though subsequent development of visible injury may be as much a property of basic plant metabolism (44), it is necessary that stomata be open during exposure to the gas (42, 43) in order for leaves otherwise potentially ozone-sensitive to manifest injury symptoms. Thus, after the primary tissue barrier to gaseous exchange is traversed, the second barrier is the plasma membrane. Recent work has shown that ozonation can disrupt ion and water flux at the plasma membrane (45, 46), While membrane functional disturbance need not be indiscriminate (25, 46), the cited work supports the suggestion that cellular membranes represent a principal locus of ozone action (10, 39, 47, 48),... 

Scavengers present in water (e.g., HCO3, S2", NOj, Br ) decrease ozone s effectiveness due to their reaction with OH radicals, which are essential intermediates in the mechanism for ozone action. 

The dilution effect seems to be fairly characteristic of the ozone action upon autoxidation. The logical method of investigation would be to use oxygen-ozone mixtures in all proportions, including mixtures having exceedingly low concentrations of oxygen. 

When solid polystyrene is subjected to an ozone attack, carbonyl, peroxide, and carboxylic acid groups form on the surface of the polymer [528]. The reaction rate is proportional to the concenttation of the ozone and the surface of the sample. As a result of the ozone action, intramolecular cross-linking takes place. The reaction mechanism of the ozone attack on polystyrene can be shown as follows [528] ... 

The first studies on the reaction of ozone with paraffins have been carried out with methane, ethane, propane and butane in gas phase [2-8], It has been established that the absorption of 1 mol ozone yields 1 mol products. The analysis of the experimental data reveals two mechanisms of ozone action 1) ozone is decomposed to atomic oxygen, which initiates the oxidation process [2] mechanism - (M.1.1) and 2) ozone interacts directly with the alkane [3-5] mechanism - (M.I.2.) ... 

The marked decrease of m.p. (12-24 C) upon PP ozonolysis could not be explained by the increase of cr of the crystallites as they simply disappear. More probably the amorphization is connected to destroy of crystallites as a result of the ozone action. Actually, in the DSC curves of the ozonized mixtures with 0-40% PP content crystallites are not observed while in the IR spectra the amount of the CHj groups is not altered. Ozone reacts with the tertiary hydrogen bong in the amorphous and crystal part. The former leads to increase of the number of defects which facilitates the subsequent ozone access. Thus the crystallites are destroyed and further get amorphized. 

The ozone action [92, 102] is very important for the utilization of polymeric materials in various domains, especially in strong electric fields. The peculiarity of the ozone oxidation is short kinetic chain, high radical concentration, greater share of the ozone with intermediate radicals, as well as the localization of the process at the surface and in amorphous regions. For example, the following reactions can take place ... 

At ozone concentration of 8 mg/1 in water, only 6% of Scendezmus algae remain alive after 10-15 min. However, it is to be noted that the ozone action on the various algae is quite different and specific. Thus As-tetionella type algae are very ozone resistant. 

The manufacture of pour point depressants for oils, particularly usefiil for diesel oils, is carried out by oxidative degradation of waste polyethylene and/or polypropylene (I) with ozone at 30-150 C. 1000 g waste (I) is exposed to ozone action at 150°C for 5 h giving the pour point depressant. The addition of 1 % depressant to diesel oil leduees the solidifieation of the oil from -20°C to -35°C and the temperature of filter plugging from -9 to -20°C [133]. 

We have studied the effect of ozone [191] on POL of rabbit brain and liver. In this connection the rabbits were exposed to ozone action in a special chamber for 2, 3, 10 and 15 h. The ozone concentration in the gas phase was varied in the range 50-250 ppm. We have found a substantial enhancement of the content of endogenous POL fluorescence products (FP) and TBA-reacting products (TBA-rp) after 2 h exposure to 250 ppm ozone concentration. However, after 4 h exposure to the same ozone concentration the rabbits die. When the concentration of exposed ozone was 50 ppm the increase in FP content in the rabbits brain is increased by about 1.8 times after 10 h, and in the liver - by about fold 2 compared with that of the control test. The level of TBA-rp was 3.1 and 3-fold higher, respectively. It has been observed that the amount of FP in the brain between the 10th and 15th h does not change, but the FP content in the liver microsomes rises 2.6 times and that of TBA-rp - 3. 6 fold. A series of test animals, which were preliminary injected with 56 mg/kg potassium salt of DL-a-tocopherol 10 h before the test, were also studied under the same conditions. The results from FP determination after 10 and 15 h of exposure reveal that their amount in the brain has increased by 1.09 and 1.3 times, respectively and in the liver microsomes -1.5 and 1.9 fold. Simultaneously there is no marked difference in the DL-a-tocopherol content before and after exposure of the test animals as demonstrated by the HPLC data. These facts indicate that the brain is either more stable or more pro-... 

Ozone is formed in certain chemical reactions, including the action of fluorine on water (p. 323) and the thermal decomposition ofiodic(VII) (periodic) acid. It is also formed when dilute (about 1 M) sulphuric acid is electrolysed at high current density at low temperatures the oxygen evolved at the anode can contain as much as 30% ozone. 

Ozone (O3), a highly active compound, is formed by the action of an electrical discharge or ultraviolet light on oxygen. 

Ozone, which occurs in the stratosphere (15—50 km) in concentrations of 1—10 ppm, is formed by the action of solar radiation on molecular oxygen. It absorbs biologically damaging ultraviolet radiation (200—300 nm), prevents the radiation from reaching the surface of the earth, and contributes to thermal equiHbrium on earth. 

Ozone is formed rapidly in the stratosphere (15—50 km) by the action of short-wave ultraviolet solar radiation (<240 nm) on molecular oxygen,... 

The relinking (14) and self-healing film (3) theories require chemical interaction between the antiozonant and ozonized mbber. The evidence for these interactions is meager (35,36). Overall, there seems to be no clear evidence in the Hterature for PDA derivatives becoming attached to mbber chains as a result of ozone attack. Much fundamental work in this area remains to be done, however. It seems clear at this point that any antiozonant—mbber interaction must be much less important than the scavenging effect of the antiozonant. In summary, the scavenger model is beheved to be the principal mechanism of antiozonant action. Ozone—antiozonant reaction products form a surface film that provides additional protection (37). 

It was not their reactivity but their chemical inertness that was the true surprise when diazirines were discovered in 1960. Thus they are in marked contrast to the known linear diazo compounds which are characterized by the multiplicity of their reactions. For example, cycloadditions were never observed with the diazirines. Especially surprising is the inertness of diazirines towards electrophiles. Strong oxidants used in their synthesis like dichromate, bromine, chlorine or hypochlorite are without action on diazirines. Diazirine formation may even proceed by oxidative dealkylation of a diaziridine nitrogen in (186) without destruction of the diazirine ring (75ZOR2221). The diazirine ring is inert towards ozone simple diazirines are decomposed only by more than 80% sulfuric acid (B-67MI50800). 

Note Append to each entry Meterological conditions are such that pollutant concentrations can be expected to remain at the above levels for 12 or more hours or increase, or in the case of ozone the situation is likely to reoccur within the next 24 hours unless control actions are taken. 

Free-radical initiation of the chain reaction of oxidation can arise from the action of heat, light, metal ions and, sometimes, ozone on a variety of chemical moieties such as those indicated in Table 7.4. 

SIPs are intended to prevent air pollution emergency episodes. The phms are directed toward preventing excessive buildup of air pollutants tliat me known to be harmful to the population and the enviroiunent when concentrations exceed certain limits. The compounds affected under the implementation plans are sulfur dioxide, particulate matter, ctirbon monoxide, nitrogen dioxide, and ozone. A contingency plan, which will outline the steps to be taken in tlie event tliat a particular pollutant concentration reaches tlie level at wliich it can be considered to be hannful, must be included in each implementation plan. The implementation plans are solely based on tlie continuous emission of tlie previously stated air pollutants. They do not mandate any actions to be taken in tlie event of an accidental toxic release. 

Thus, the mean temperature of the atmosphere, which is about 20°C at sea level, falls steadily to about —55° at an altitude of 10 km and then rises to almost 0°C at 50 km before dropping steadily again to about —90° at 90 km. Concern was expressed in 1974 that interaction of ozone with man-made chlorofluorocarbons would deplete the equilibrium concentration of ozone with potentially disastrous consequences, and this was dramatically confirmed by the discovery of a seasonally recurring ozone hole above Antarctica in 1985. A less prominent ozone hole was subsequently detected above the Arctic Ocean. The detailed physical and chemical conditions required to generate these large seasonal depletions of ozone are extremely complex but the main features have now been elucidated (see p. 848). Several accounts of various aspects of the emerging story, and of the consequent international governmental actions to... 

The work of Harries and Himmelmann provides considerable confirmation of the individuality of the aldehydes citronellal and rhodinal. By the action of ozone on the aldehyde, results differ materially according to the source of the citronellal, and those chemists are of opinion that the two complexes—... 

It is clear that human action can affect seven of eight of the major gi eenhouse forcings carbon dioxide, methane, nitrous oxide, ozone, CFCs, aerosols, and water vapor. As studies of solar variation have shown, it is also clear that human action is not the only factor involved in determining the impact of these forcings. There is still substantial uncertainty regarding the actual climate impact of the climate forcings. 

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