Photochemical smog chamber

Akimoto, H., M. Hoshino, G. Inoue, F. Sakamaki, N. Washida, and M. Okuda, Design and Characterization of the Evacuable and Bakable Photochemical Smog Chamber, Environ. Sci. Technol., 13, 471-475 (1979). 

Sakamaki, F., and H. Akimoto, HONO Formation as Unknown Radical Source in Photochemical Smog Chamber, lnt. J. Chem. Kinet, 20, 111-116(1988). 

This comprehensive databank ineludes photochemical smog chamber studies on the four classes of mono-aromatic compounds above (carried out under suitable atmospheric conditions) as well as a series of experiments looking into specific key areas of aromatic photo-oxidation, focussing on subsets of die toluene system. Results from this system ean be transferred to other aromatics as the mechanisms are expected to be similar. Where appropriate, results from diis database have been used to refine the mechanisms. 

Fig. 7.5 Evacuable photochemical smog chamber at National Institute for Environmental Studies, Tsukuba, Japan...

In this paragraph, dependence of O3 production on NO and VOC concentrations under the conditions of polluted urban atmosphere is summarized referring to the photochemical smog chamber experiments (see Column 2 p. 317). The almost sole reaction of direct O3 formation in the troposphere is the reaction of O2 with the ground state oxygen atom 0( P) from the photolysis of NO2,... 

Akimoto, H., Hoshino, M., Inoue, G., Okuda, M. Reaction mechanism of the photooxidation of the toluene-N02-02-N2 system in the gas phase. Bull. Chem. Soc. Jpn. 51, 2496-2502 (1978) Akimoto, H., Hoshino, M., Inoue, G., Sakamaki, F., Washida, N., Okuda, M. Design and characterization of the evacuable and bakable photochemical smog chamber. Environ. Sci. Technol. 13, 471 75 (1979a)... 

Table 2-6 is a list of some compounds that may be present in photochemical smog, but have not yet been reported. The presence of some of these compounds (such as PBzN and ketene) seems very probable, in diat they have been observed in smog-chamber studies, whereas others are... 

The diurnal patterns of ozone, nitric oxide, and nitrogen dioxide concentrations observed during photochemical oxidant episodes in California have been confirmed by smog-chamber studies. There may be, however, a decrease in reliability with decreasing concentration of values less than 0.1 ppm that were measured by the colorimetric method. The magnitude of these uncertainties among the various monitoring networks in the United States has still to be assessed. 

Smog chamber studies have documented similar aerosol growth mechanisms. For example, in the photochemical oxidation of dimethyl sulfide, the formation and growth of particles in an initially particle-free system was observed. However, if seed particles with 34-nm mean size were present, an oscillation in the... 

The results from such chamber studies are frequently used to test the chemical portion of various computer models for photochemical air pollution in order to provide a scientific basis for control strategies. While the interpretation of the results of smog chamber studies and their extrapolation to atmospheric conditions also have some limitations (vide infra), such studies do provide a highly useful means of initially examining the emissions-air quality relationship under controlled conditions. 

Clearly, environmental chamber studies are very useful tools in examining the chemical relationships between emissions and air quality and for carrying out related (e.g., exposure) studies. Use of these chambers has permitted the systematic variation of individual parameters under controlled conditions, unlike ambient air studies, where the continuous injection of pollutants and the effects of meteorology are often difficult to assess and to quantitatively incorporate into the data analysis. Chamber studies have also provided the basis for the validation of computer kinetic models. Finally, they have provided important kinetic and mechanistic information on some of the individual reactions occurring during photochemical smog formation. 

However, despite these complications, smog chambers have proven extremely useful in studying the chemistiy of photochemical air pollution under controlled conditions in which emissions and meteorology are not complicating factors. While there are some... 

Behnke, W., W. Hollander, W. Koch, F. Nolting, and C. Zetzsch, A Smog Chamber for Studies of the Photochemical Degradation of Chemicals in the Presence of Aerosols, Atmos. Environ., 22, 1113-1120 (1988). 

Dodge, M. C., Combined Use of Modeling Techniques and Smog Chamber Data to Derive Ozone-Precursor Relationships, in Proceedings of the International Conference on Photochemical Oxidant Pollution and Its Control (B. Dimitriades, Ed.), EPA-600/3-77-001b, Vol. II, pp. 881-889, 1977a. 

Evans, L. F I. A. Weeks, and A. J. Eccleston, A Chamber Study of Photochemical Smog in Melbourne, Australia—Present and Future, Atmos. Environ., 20, 1355-1368(1986). 

In later experiments, Izumi et al. (47, 48) examined aerosol formation during photooxidation of a variety of hydrocarbons in an evacuable smog chamber. No seed particles were used in these experiments, but good estimates of the yield of aerosol from photochemical oxidation of the hydrocarbon precursors were obtained by using EAA data. In some cases, the volumetric yield was found to decrease with decreasing precursor concentration (Figure 4), so the finite vapor pressure of the reaction products limited nucleation, particle growth, or both. 

Fig. VI-9. Concentration-lime history or reactants and some products in the photooxidation of C3H. Mixtures of C,H4 + NO + NOj in air were irradiated by simulated sunlight in smog chamber. Reprinted with permission from H. Niki, C. E. Daby, and B. Weinstock, in Photochemical Smog and Ozone Reactions, R. F. Gould, Ed., American Chemical Society, Washington, D. C. Copyright by the American Chemical Society, 1972. 

Photochemical smog contains N02, the gas responsible for the brown blanket over larger cities. This gas can produce a dimer (two identical units chemically bonded) by the reaction, 2N02 —> N204. If the reaction of 750 g N02 goes all the way to the right, what will be the pressure in a 10-L chamber at 42°C ... 

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