Measurements of ozone

Measurements of ozone (O3) concentrations in the atmosphere are of particular importance. Ozone absorbs strongly in the ultraviolet region and it is this absorption which protects us from a dangerously high dose of ultraviolet radiation from the sun. The vitally important ozone layer lies in the stratosphere and is typically about 10 km thick with a maximum concentration about 25 km above the surface of the earth. Extreme depletion of ozone in a localised part of the atmosphere creates what is known as an ozone hole. 

Measurements of ozone concentration in the ozone layer in the stratosphere are made in the less intense Huggins band to avoid complete absorption of the laser radiation. Again, the two or three wavelength DIAL method is used to make allowance for background aerosol scattering. A suitable laser for these measurements is the XeCl pulsed excimer laser (see Section 9.2.8) with a wavelength of 308 nm, close to the peak absorption of the Huggins... 

Ozone can be analyzed by titrimetry, direct and colorimetric spectrometry, amperometry, oxidation—reduction potential (ORP), chemiluminescence, calorimetry, thermal conductivity, and isothermal pressure change on decomposition. The last three methods ate not frequently employed. Proper measurement of ozone in water requites an awareness of its reactivity, instabiUty, volatility, and the potential effect of interfering substances. To eliminate interferences, ozone sometimes is sparged out of solution by using an inert gas for analysis in the gas phase or on reabsorption in a clean solution. Historically, the most common analytical procedure has been the iodometric method in which gaseous ozone is absorbed by aqueous KI. 

Sheeter [17] has discussed an ultraviolet method for the measurement of ozone in seawater. Crecelius [18] has discussed oxidation products obtained (bromine, hypobromous acid, bromate) when bromides in seawater are oxidised by ozone. 

Approximately the first third of this report is concerned with the origins and measurement of ozone and other photochemical oxidants and the relationship of atmospheric concentrations to emissions. The middle third deals with toxicologic studies and effects on humans, and the last with effects on plants, ecosystems, and materials. 

The airborne monitoring program concentrated on the measurement of ozone to provide supplementary air quality data for various altitudes over the fixed sites. The airborne measurements were conducted in a C-45 aircraft that carried a solid-face chemiluminescent ozone monitor. The ozone meter was cycled every 2 min to provide calibration, purge, measurement, and purge at equal intervals. The sparseness of the airborne data precluded... 

Sticksel discussed vertical profile measurements of ozone in the stratosphere and the troposphere over the last several years. Transient ozone maximums in the troposphere are illustrated and explained by three possible mechanisms a channel-like r on conducted ozone from the stratosphere into the troposphere ozone-laden air descended from the stratosphere and was compressed as it subsided and ozone-rich layers leaked through the break between the polar and middle tropopauses by differential advection. Surface variations of ozone soundings were mostly attributed to anthropogenic pollution however, relatively thick high-... 

In addition to the specificity of the monitoring method, an important requirement for the measurement of atmospheric pollutants is the accuracy of the calibration technique. The calibration procedure for the measurement of oxidants or ozone utilizes a stable and reproducible sample of dilute ozone in air. The ozone concentration of this sample is established with a reference method that is not necessarily suitable for monitoring ambient air. This reference method must agree with the scientifically accurate measurement of ozone in the calibration sample. 

Because of the interference problems with both colorimetric and amperometric analyzers, they are being replaced by instruments based on other principles. (Colorimetric analyzers are no longer commercially available.) One such recently improved technique developed for the specific detection and measurement of ozone is the detection of the... 

Measurement of ozone and oxidants. See also Ozone concentration, measurement of Photochemical-oxidant concentration, measurement of calibration procedure for, 242, 249-50 for ozone analysis, 252-59 for ozone generation, 251-52 transferable standards for, 255 evaluation of data from, 273-76 recommended research on, 262, 273-76, 699-700... 

After the first reports of this phenomenon, major field campaigns were launched, which clearly established a relationship between ozone destruction and chlorine chemistry. For example, Fig. 1.8 shows simultaneous aircraft measurements of ozone and the free radical CIO as the plane flew toward the South Pole. As it entered the polar vortex, a relatively well-contained air mass over Antarctica, 03 dropped dramati-... 

Droppo, J. G Jr., Concurrent Measurements of Ozone Dry Deposition Using Eddy Correlation and Profile Flux Methods, J. Geo-phys. Res., 90, 2111-2118 (1985). 

Detection techniques. Detection techniques for surface-based measurements of ozone include (1) UV absorption at 254 nm (2) chemiluminescence on reaction with NO (or ethene) (3) DOAS (4) TDLS and (5) wet chemical methods, mainly those involving the oxidation of I to 12 and measurement of the I2 colori-metrically or coulometrically. The wet chemical method and the principles behind DOAS and TDLS were discussed earlier and are not treated further here. 

Electrochemical (amperometric) techniques provide the possibility for in situ, continuous and automated measurements of ozone in the liquid. The membrane electrode usually consists of a gold cathode, a silver anode, an electrolyte (e. g. AgBr, K2S04 or KBr) and a teflon membrane. Several companies offer such electrodes in different configurations. The application range and accuracy differs depending on the kind of electrode. 

Stanley J H, Johnson J D (1979) Amperiometric Membrane Electrode for Measurement of Ozone in Water, Analytical Chemistry 51 2144-2147. 

Suga34 suggests that the air flow and filtering system normally used may be inadequate and proposes that improvement to the carbon purifier is needed to exclude all pollutant gases which can interfere with the measurement of ozone concentration. Presumably, this depends on the atmosphere in which the cabinet is housed. They also found that gases could be given off by the rubbers under test which also affect the measured ozone concentration, and a filter in the measuring system is needed so that compensation can be made. 

It has also been shown54 that T50 test pieces can be successfully used with complete fracture as the criterion of failure. This obviously results in a longer test but the means of assessment is much easier and not subjective. Although rupture is not widely used as a measure of ozone attack it is used in fatigue tests (Chapter 12) and could possibly be used for static ozone tests. 

The difference between the concentration of 03 and 03s is a measure of ozone that originates from photochemistry in the troposphere, referred to as 03t. The modeled 03, 03s and 03t fields from the three simulations are used to calculate budgets of chemistry and of transports within the troposphere and between the stratosphere and the troposphere, and to estimate the impact of STE on tropospheric 03 levels. 

Marenco, A., et al. (1998) Measurement of ozone and water vapor by Airbus in-service aircraft The MOZAIC airborne program, an overview, J. Geophys. Res. 103, 25631-25642. 

Rusch, D.W., G.H,. Mount, C.A. Barth, RJ. Thomas and M.T. Cal Ian (1984) Solar mesospheric explorer ultraviolet spectrometer, measurements of ozone in die 1.0-0.1 ntbar region. Journal of Geophysical Research 84 11677-11687. 

Altitude-resolved measurements of ozone and other constituents are necessary for improving our knowledge of physical and chemical processes in the stratosphere. Limbviewing satellite instruments can measure density profiles of stratospheric constituents at a good altitude resolution (1-3 km). In addition, satellite-based measurements have a global geographical coverage. 

JIS X 6936 2005 Information technology- Office equipment-Measurement of ozone, volatile organic compounds and dust emissions rate from copiers, printers and multifunction devices ECMA-328... 

Freeman, D.E., Yoshino, K., Esmond, J.R., and Parkinson, W.H. (1984). High resolution absorption cross-section measurements of ozone at 195 K in the wavelength region 240-350 nm, Planet. Space. Sci. 32, 239-248. 

Determination of several atmospheric oxidant species is critical to understanding gaseous and aqueous processes leading to acidic deposition. Hydrogen peroxide has a high Henry s Law solubility and must be measured in gaseous and aqueous atmospheric samples to better understand wet deposition processes. In contrast, measurements of ozone and peroxyacyl nitrates (PANs) (and probably alkyl hydroperoxides and peracids) usually need to be made only in the gas phase due to their low aqueous solubility (14). 

Note 3. The ozone generator was a Welsbach model T-408 operated at 95 V. Measurement of ozone concentration at its source, or of unconsumed ozone during sample treatment, may be made by titration of the iodine generated from aqueous potassium iodide solutions placed in downstream bubblers. 

British scientists from the British Antarctic Survey (BAS) had been making measurements of ozone from their base at Halley Bay (76°S) for many years. They detected a decline in the springtime ozone since 1977, and by October 1984, they had detected a 30% decline in the total ozone. Today, this value has reached 60%. The ozone hole begins to develop in August, is fully developed by early October and has normally broken up by early December (see Figure 28). 

The large fluctuations with altitude that are frequently observed in tropospheric measurements of ozone and water number densities suggest that vertical eddy diffusion with a constant diffusion coefficient is not adequate. 

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