Ozone concentration in air

These iodometric calibration methods are based on the assumption that there is a stoichiometric reaction between ozone and the iodine in the various potassium iodide procedures. Three essentially independent methods have been used to test the accuracy of this assumption measuring the absorption of ultraviolet radiation at 254 nm by ozone in air, measuring the absorption of infrared radiation at 9,480 nm by ozone in air, and determining the ozone concentration in air by titration with nitric oxide. 

Normal ozone dosage per cubic meter of water, 0.4 gram Ozone concentration in air. 10 grams per cubic meter Retention time of water in ozonation chamber, about 10 minutes... 

Temperature Effeet on Ozone Stability. Based on enthalpy released during the ozone decomposition (6-63), calculate the relative O3 concentration in air that can lead to a doubling of initial room temperature of the air (heating to a temperature of about 600 K). Estimate the characteristic time of ozone decomposition (6-81) at this relative ozone concentration in air, and at this temperature (about 600 K). 

Belysheva TV, Gerasimov GN, Gromov VF, Trakhtenberg LI. The sensor properties of Fe203 center dot Iu203 films The detection of low ozone concentrations in air. Russ. J. Phys. Chem. A 2008 82(10) 1721-1725. DOI 10.1134/ S0036024408100142. 

In air, in the absence of additives, NO removal takes place by oxidation [56-58], Wu et al. [56] observed that the concentration of ozone generated in the corona discharge in the presence of NO is significantly smaller as compared to the ozone formed in air without NO under the same conditions. Thus, they concluded that NO oxidation by ozone and atomic oxygen is an important reaction path for the NO conversion. 

FIGURE 2-1 Diurnal variation of nitric oxide, nitrogen dioxide, and ozone concentrations in Los Angeles, July 19, 1965. Reprinted from Air Quality Criteria for Photochemical Oxidants. ... 

Lasers, to study air chemistry, 36-37, 674 Leaves. See abo Pl ts sensitivity to ozone, 443, 511, 512, 686 stomata of, as sites for ozone and PAN entry into plants, 10, 446, 686 lichens, response to oxidants, 549 Life cycle of plants, effect of ozone on, 460 light, effect of, on plants sensitivity to oxidants, 480-84 lipids, effect of ozone on, 346-50 Liver, effect of ozone on, 355 London, England, ozone concentration in, 139,143... 

The interplay of HO, peroxy radicals, VOCs, and NO , species has substantial implications for tropospheric air quality. For instance, VOCs, NO , , and sunlight result in poor visibility from ozone and aerosol formation, together denoted as photochemical smog, which can lead to adverse health effects in sensitive individuals. Normally, we think of minimizing either class of compounds as beneficial to the atmosphere. However, minimizing VOC emissions only impacts ozone concentration in high-NO , areas. Moreover, in VOC-sensitive areas, reductions in NO , may lead to the overproduction of ozone. We can examine a simplified scheme for ozone production ... 

In some cases, the compound itself is sufficiently unstable that it cannot be purchased and must be synthesized. This is the case for compounds such as 03 and HONO. Ozone at ppb to ppm concentrations in air is generated either by photolyzing 02, e.g., using a low-pressure mercury lamp, or by a discharge in 02 ... 

Developing control strategies for ozone is very different than for relatively unreactive species such as CO. In the latter case, the concentrations in air are a direct result of the emissions, and all things being equal, a reduction in emissions is expected to bring about an approximately proportional reduction in concentrations in ambient air. However, because O, is formed by chemical reactions in air, it does not necessarily respond in a proportional manner to reductions in the precursor emissions. Indeed, as we shall see, one can predict, using urban airshed or simple box models, that under some conditions, ozone levels at a particular... 

Theoretically, almost fivefold higher ozone concentrations in the gas can be achieved with pure oxygen compared to air. State-of-the-art full-scale EDOGs achieve cc = 3—4 wt % from air and 10-13.5 wt % from oxygen. Lab-scale systems can produce up to 20 wt % ozone (302 g 03 m-3 at STP) from pure oxygen. 

Ambient air ozone monitor. Is it necessary to check the ambient air ozone concentration in the lab Yes, it is highly recommended to control the lab environment and connect the monitor to the ozone generator so that the ozone production will be shut off in case of leakage in the system B 2.5... 

In addition to OH radicals, unsaturated bonds are reactive towards O3 and NO3 radicals and reaction with these species is an important atmospheric degradation mechanism for unsaturated compounds. Table 4 lists rate constants for the reactions of 03 and NO3 radicals with selected alkenes and acetylene. To place such rate constants into perspective we need to consider the typical ambient atmospheric concentrations of O3 and NO3 radicals. Typical ozone concentrations in pristine environments are 20-40 ppb while concentrations in the range 100-200 ppb are experienced in polluted air. The ambient concentration of NO3 is limited by the availability of NO sources. In remote marine environments the NO levels are extremely low (a few ppt) and NO3 radicals do not play an important role in atmospheric chemistry. In continental and urban areas the NO levels are much higher (up to several hundred ppb in polluted urban areas) and NO3 radicals can build up to 5-100 ppt at night (N03 radicals are photolyzed rapidly and are not present in appreciable amounts during the day). For the purposes of the present discussion we have calculated the atmospheric lifetimes of selected unsaturated compounds in Table 4 in the presence of 100 ppb (2.5 x 1012 cm 3) of O3 and 10 ppt (2.5 x 108 cnr3) of NO3. Lifetimes in other environments can be evaluated by appropriate scaling of the data in Table 4. As seen from Table 4, the more reactive unsaturated compounds have lifetimes with respect to reaction with O3 and NO3 radicals of only a few minutes ... 

Figure 1 Peak ozone concentrations in the eastern United States during a severe air pollution event (June 15, 1988) based on surface observations at 350 EPA monitoring sites. The shadings represent values of 30-60 ppb (lightest shading) to 180-210 ppb (darkest shading) with 30 ppb intervals in between. Values reported for Canada and the Atlantic Ocean are inaccurate, since no observations were available for these locations (first printed in Sillman, 1993) (reproduced by permission of Annual Reviews from Annual Reviews of Energy and the Environment, 1993,18, 31-56).

These values show clearly the pronounced accelerating action of ozone upon the autoxidation rate this action becomes still more pronounced, if the ozone concentration in oxygen or in air is diminished. 

Evacuation of the air before introduction of the ozone under pressure allows a high concentration of ozone to be reached quickly in the bottle. The result is an appreciable reduction in the sterilization cycle. Figure 2 illustrates the difference between sterilizing without first evacuating the air, and sterilization according to the method at present used. Curve B illustrates the process employed at Sissach. It indicates the variations of ozone concentration in the bottle during the sterilization cycle, expressed in per cent of the maximum concentration recorded at the end of the operation. At the end of the second second of time, the bottle contains a concentration equal to 80% of the concentration recorded at the end of the operation. 

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