Error ozone measurement

Box 3-2 Case Study Systematic Error in Ozone Measurement ... 

As can be seen in Fig. 7.10, the larger Ru nanoparticles are more reactive than the smaller Ru nanoparticles. These results are consistent with the reports of several research groups, as described earlier, that larger Ru nanoparticles show higher catalytic activity due to enhanced stability of the core-shell-type surface oxide layer on the Ru metallic core [36, 48, 50]. We also see that the TOF of Ru nanoparticles decreases after UV-ozone treatment. The activation energy of the 2.8 nm Ru nanoparticles remained the same, within the error of measurement, while that of the 6 nm Ru nanoparticles increased from 33.2 to 38.7 kcal/mol after UV-ozone... 

A diagram of a typical gas-phase (ozone-ethylene) chemiluminescent ozone analyzer is shown in Figure 6-10. The detector responds linearly to ozone concentrations between 0.003 and 30 ppm no interferences were initially observed. More recently, however, it has been established that, as the relative humidity goes from 0 to 60% and the temperature from 20° to 25° C, water vapor produces a small positive signal that results in an increase of about 8% in the ozone concentration measurement. This potential source of error can be minimized by using humidified, rather than dry, ozone in air streams when calibrating. 

Fig. 13.9a. Cunnold et al. (1996) indicate that these errors in accurately extracting the aerosol contribution were responsible for about half of the discrepancy and increases in tropospheric ozone the other half. Similar discrepancies between SAGE measurements and the results from other techniques such as ozonesondes have also been reported and attributed largely to the problem of accurately removing the aerosol particle contributions (e.g., Veiga et al., 1995 Steele and Turco, 1997b).

The statistical comparisons between ozone forecasts and measurements for all stations in eastern Austria show correlation coefficients between 0.4 and 0.7 and standard errors around 12 ppbv for 2006. 

Nitric Oxide. Since photolysis of NO2 did not proceed measurably before irradiation, as indicated by zero ozone readings for systems containing NO2 in zero air, the NO readings obtained before irradiation for these systems and for the system of Figure 1 are artifacts of the analytical method. The positive error is probably attributable to the scrubbing column used to remove NO2 before the NO oxidation step. Either less... 

By the use of measured volumes of liquid ozone at low temperature, liquid ozone-oxygen mixtures are prepared without ozone decomposition. Techniques for the preparation, mixing, disposal, and measurement of the physical properties of these mixtures are described at the liquid phase boundaries at —183 and —195.5° C., the specific volume of ozone-oxygen mixtures is additive within experimental error (0.005 gram per cc). The viscosity of solutions at —183° C. (on a log scale) varied linearly with the composition from 0.189 cp. for 100% oxygen to 1.57 cp. for 100% ozone. At —195.5° C., the viscosity of supercooled liquid ozone is 4.20 cp. Single phase liquid ozone-oxygen mixtures are Newtonian fluids. The surface tension of liquid ozone is 43.8 and 38.4 dynes per cm. at —195.5° and —183°C., respectively. The parachor of liquid ozone is 76.5. 

The deviation from additive volumes is less than the experimental error for the four solutions measured. The density of the solutions may be calculated to 0.3% from the sum of the volumes of liquid ozone and oxygen ... 

Measurements away from industry and cities gave comparable values (5), but large errors arose from smoke and industrial contamination. These components, brought into the solution with the air, reduce iodine. As their reaction is not distinguishable from the action of sodium thiosulfate, the ozone content calculated is low. With severe contamination by smoke, negative ozone values are found. 

The photometric evaluation of the spectra has to be carried out very carefully. The transmittance of the three-stage filter employed in front of the slit was calibrated by means of a physical method (Fraunhofer diffraction) (11, 12). A special procedure was used for checking the path of the three intensity curves of the spectrum (6). As a result of all these precautions, an accuracy to 1.5% for a single measurement of x(h) was obtained. The errors in (/i) then amount to 1, 0.5, and 0.3 X lO cm. of ozone per km. for altitudes of 5, 25, and 30 km., respectively. 

Providing these biofilters only contain beneficial bacteria that are involved in this breakdown of ammonia then they pose little risk to the larvae. If the biosecurity breaks down due to say, operator error, and a pathogen is introduced it may become established in the biofilm with the biofilter and become a more permanent member of the bacterial community. In this situation, there is the potential for the filter to shed pathogens into the water column with subsequent infection of the production larvae. This situation is very difficult to eradicate. Control measures may include installation of UV or ozone after the biofilters to kill any shed bacteria before the water enters the production area or the breakdown and sterilization of the larval production system. 

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