Ultraviolet ozone monitor

Kleindienst, T. E E. E. Hudgens, D. F. Smith, F. F. McElroy, and J. J. Bufalini, Comparison of Chemiluminescence and Ultraviolet Ozone Monitor Responses in the Presence of Humidity and Photochemical Pollutants, J. Air Waste Manage. Assoc., 43, 213-222 (1993). 

Kleindienst TE, Hudgens EE, Smitli DF, et al. 1993. Comparison of chemiluminescence and ultraviolet ozone monitor responses in the presence of humidity and photochemical pollutants. J Air Waste Manage Assoc 43 213-222. 

Methods of measuring the components of photochemical smog are reviewed in Chapter 6. There have been significant advances in the calibration of instruments for monitoring ozone in ambient air. A method based on the absorption of ultraviolet radiation at 254 nm has been adopted by California for the calibration of air monitoring instruments. The method is based on the use of a commercially available instrument that measures ultraviolet absorption as a transfer standard in the calibration process. 

Instruments based on differential ultraviolet absorption still need to be evaluated, and possibly modified, before their acceptance for monitoring ozone in polluted atmospheres on a nationwide scale. The California Air Resources Board and other air pollution control agencies are evaluating ultraviolet absorption with both chemiluminescence and potassium iodide instruments. 

The analytic principles that have been applied to accumulate air quality data are colorimetry, amperometry, chemiluminescence, and ultraviolet absorption. Calorimetric and amperometric continuous analyzers that use wet chemical techniques (reagent solutions) have been in use as ambient-air monitors for many years. Chemiluminescent analyzers, which measure the amount of chemiluminescence produced when ozone reacts with a gas or solid, were developed to provide a specific and sensitive analysis for ozone and have also been field-tested. Ultraviolet-absorption analyzers are based on a physical detection principle, the absorption of ultraviolet radiation by a substance. They do not use chemical reagents, gases, or solids in their operation and have only recently been field-tested. Ultraviolet-absorption analyzers are ideal as transfer standards, but, as discussed earlier, they have limitations as air monitors, because aerosols, mercury vapor, and some hydrocarbons could, interfere with the accuracy of ozone measurements made in polluted air. 

Differences in measurement methods include analyzer systems based both on the same and on different measurement principles. The average standard deviation in the performance of different chemiluminescent ozone instruments that are sampling the same ambient air both with and without an added ozone concentration of 0.(X)2-0.5 ppm is 6-10%. Field studies comparing an ultraviolet monitor with several chemiluminescent monitors showed correlation coefficients for hourly averages of 0.80-0.95 between various pairs of instruments. Hourly averages for about 500 pairs of values at ambient ozone concentrations of 0.005-0.100 ppm showed deviations of 3-23% between the average values for paired instruments. 

Hodgeson, J. A., C. L. Bennett, H. C. Kelly, and B. A. Mitehell. Ozone measurements by iodometiy, ultraviolet photometry and gas-phase titration. Paper Presented at the American Society for Testing and Materiak Conference on Calibration in Air Monitoring, Boulder, University of Cdorado, Aug. 5-7, 1975. 

McGrath and Morrow " studied the reactions of both 0( D) and 0( P) with cyanogen at room temperature by flash photolysis. The 0( D) was produced by the photolysis of ozone. The reaction was monitored by absorption spectroscopy. At first, they attributed the previously unidentified ultraviolet absorption bands at 3250-3330 A to the fulminate radical (CNO), concluding that the initial step of the reaction was... 

Instrumentation for the research was developed prior to formulation of the problem. This fortunate situation arose because the instruments were developed for monitoring the lower atmosphere for ozone, nitric oxide, and nitrogen dioxide these compounds are usually present in polluted atmospheres at concentrations below 1 p.p.m. by volume. On hand were an automatic recording nitrogen dioxide analyzer (11), a neutral potassium iodide oxidant recorder (5), and an ozone photometer (Model 53 ultraviolet, Harold Kruger Instruments, San Gabriel, Calif.). Each of these instruments has a sensitivity of 1 to 2 p.p.hm. parts of carrier gas at atmospheric pressure. Without their prior development, the photochemical study would have been impossible. 

The solar spectrum has been the subject of numerous rocket experiments undertaken since the 1940s. The first spectrum measured above the ozone layer by a V-2 rocket dates from October 1946 (Baum et al, 1946), and not until the 1950s was a solar spectrum observed from an altitude of 100 km (Johnson et al, 1952). Today the solar irradiance is routinely observed by spectrometers on board balloons, aircraft, or spacecraft. During the 1990s, for example, the solar UY flux was measured almost continuously between 120 and 400 nm by the Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) and the Solar/Stellar Irradiance Comparison Experiment (SOLSTICE), both on board the... 

Satellite observations have added much to our understanding of the morphology of atmospheric ozone, both in terms of its altitude profile and total column density (see Box 5.3). For example, early observations by the Backscatter Ultraviolet Spectrometer (BUV) on board Nimbus 4, as well as by the Limb Infrared Monitor of the Stratosphere (LIMS), and the Solar and Backscatter Ultraviolet Spectrometer (SBUV) on board Nimbus 7 led to the first global view of the distribution of ozone... 

The ozone layer protects Earth s surface from damaging ultraviolet (UV) radiation. Therefore, if the concentration of ozone in the stratosphere decreases substantially, more UV radiation wiU reach Earth s surface, causing unwanted photochemical reactions, including reactions correlated with skin cancer. Satellite monitoring of ozone, which began in 1978, has revealed a depletion of ozone in the stratosphere that is particularly severe over Antarctica, a phenomenon known as the ozone hole ( FIGURE 18.6). The first scientific paper on this phenomenon appeared in 1985, and the National Aeronautics and Space Administration (NASA) maintains an Ozone Hole Watch website with daily updates and data from 1999 to the present. 

Due to the direct impact on the microbial state of the product, any process water that is used in the filling area has to be under strict microbial control. Next to a certain water treatment in terms of its mineral and other substance content, the microbial state should be regularly monitored. To reduce the microbial load of process (and product) water, several methods are available that shall not be further discussed here (e.g. ultraviolet treatment, microfiltration, chlorine dioxide use, ozone use and many others). 

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