Smog, origin

Although the original Clean Air Act of 1977 brought about significant improvements in air quality, the urban air pollution problems of ozone (known as smog), carbon monoxide (CO), and particulate matter (PM,o) persist. Currently, over 100 million Americans live in cities which are out of attaimnent with the public health standards for ozone. The most widespread and persistent urban... 

This is the characteristic pattern of an explanation. It begins with a Why question that asks about a process that is not well understood. An answer is framed in terms of a process that is well understood. In our example, the origin, of gas pressure in the balloon is the process we wish to clarify. It is difficult even to sense the presence of a gas. The air around us usually cannot be seen, tasted, nor smelled (take away smog) it cannot be heard or felt if there is no wind. So we attempt to explain the properties of a gas in terms of the behavior of billiard balls. These objects are readily seen and felt their behavior has been thoroughly studied and is well understood. 

Certainly, photochemical air pollution is not merely a local problem. Indeed, spread of anthropogenic smog plumes away from urban centers results in regional scale oxidant problems, such as found in the NE United States and many southern States. Ozone production has also been connected with biomass burning in the tropics (79,80,81). Transport of large-scale tropospheric ozone plumes over large distances has been documented from satellite measurements of total atmospheric ozone (82,83,84), originally taken to study stratospheric ozone depletion. 

Fig. 7-12 Schematic of an atmospheric aerosol size distribution. This shows the three mass modes, the main sources of mass for each mode, and the principal processes involved in inserting mass into and removing mass from each mode (m = mass concentration. Dp = particle diameter). (Reproduced with permission from K. T. Whitby and G. M. Sverdrup (1983). California aerosols their physical and chemical characteristics. In "The Character and Origin of Smog Aerosols" (G. M. Hidy, P. K. Mueller, D. Grosjean, B. R. Appel, and J. J. Wesolowski, eds), p. 483, John Wiley, New York.)...

Whitby, K. T. and Sverdrup, G. M. (1980). California aerosols their physical and chemical characteristics. In "The Character and Origins of Smog Aerosols" (G. M. Hidy et ai, eds). Wiley, New York. 

The main environmental issue concerned with VOCs is their ability to form low-level ozone and smog through free radical air oxidation processes. The EPA has published a list detailing a number of adverse health effects, which are now thought to originate from the presence of VOCs in the environment, including ... 

White, W.H., Robert, P.T., (1980) "On the Nature and Origins of Visibility-Reducing Aerosols in the Los Angeles Air Basin," in THE CHARACTER and ORIGINS of SMOG AEROSOLS, G.M. Hidy et al., (Editors) Wiley-Interscience, New York, Part IV, 715-753. 

Gartrell, G. Jr. Heisler, S.L. Friedlander, S.K. Relating Particulate Properties to Sources The Results of the California Aerosol Characterization Experiment. In The Character and Origin of Smog Aerosols, Hidy, G., Ed., J, Wiley, New York, 1980, 665. 

A general discussion of the nature and importance of these chamber characteristics, including wall effects, follows. For detailed descriptions of various types of smog chamber facilities and their operation, one should consult the original literature, including, for example, indoor studies utilizing borosilicate glass cylinders (Joshi et al., 1982 Behnke et al., 1988), chambers made from Teflon (FEP) film with volumes up to... 

This latter chain of reactions is responsible for all photochemical ozone formation in the troposphere, including that taking place during photochemical smog episodes, originally discovered in southern California. Such reactions can, however, also take place in background air, with ubiquitous CO and CH4 serving as fuels in the case of CO oxidation... 

One compound of interest originating from natural sources is 3-methylfuran. This pneumotoxic compound was identified in smog and is believed to arise from photodecomposition of naturally occurring terpenoids (Saunders et al. 1974). 

Smog was originally defined as a mixture of smoke and fog. Today it can also be photochemical, caused by sunlight breaking down air pollutants. 

For example, for NaCl solutions, crystallization occurs at a relative humidity of 70 percent and recrystallization appears at 40 percent. For nonhygroscopic materials, the effect does not occur. This phenomenon helps explain why smogs and hazes persist at relative humidities well below those at which they originally were formed. 

Well, the ozone concentration in the absence of the local smog tribution, it is my strong feeling that at that level the ozone is not produced in the stratosphere but is of chemical origin, driven primarily by the natural hydrocarbon oxidation cycles, as Chameides talked about yesterday. The large increase on that of course is the photochemical contribution, and there are a lot of mechanisms involved in that production term. So I do not know how far you want to dive into this question at this time. The ozone that you find in the upper troposphere may in isolated cases come directly from the strato-... 

NOjc and the Production of Ozone NO and NO2 are important air pollutants originating mainly in combustion processes. Most of the NO. formed in combustion is NO but some NO can become oxidized in the combustion process to NO2. Even small amounts of NO2 are sufficient to cause a complex series of reactions involving organics that lead to photochemical smog. The following is a simplified interpretation of the photochemical cycle of NO2, NO, and O3. (For details see Seinfeld, 1986, and Finlayson-Pitts and Pitts, 1986.)... 

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