Photochemical smog reactions

Stedman, D. H., E. D. Norris, Jr., E. E. Daby, H. Niki, and B. Weinstock. The role of OH radicals in photochemical smog reactions. Abstract WATR 26. In Abstracts of Papers. 160th National Meeting of the American Chemical Society. Chicago, September 14-18, 1970. 

Similarity solutions of the species-mass-balance equations were assumed by Friedlander and Seinfeld for a simple photochemical-smog reaction scheme. (This scheme assumed a steady-state condition for ozone.) Demonstration runs were shown for parametric variations in the... 

B. Weinstock, The Role of OH Radicals in Photochemical Smog Reactions, 160th National Meeting of the American Chemical Society, Chicago, IL, Sept. 14-18, 1970. 

Nitrogen Oxide. The photochemical smog reaction involves nitrogen oxides, hydrocarbons, and sunlight. The global importance of this pollutant system depends upon the amounts of materials emitted to the atmosphere, their residence time in the atmosphere, and their reaction products. 

Table I gives a complete statement of the mechanism reference should be made to this table throughout the following discussion. The major inorganic species that participate in photochemical smog reactions are NO, NO2, O2, CO, O3, and H2O. In Table I Reactions 1-8 and 14 represent most of the important reactions among these species and account for the following experimentally observed phenomena ...

Hess Q. D., F. Camovale. M. E., Cope, and Q. M. Johnson The evaluation of some photochemical smog reaction mechanisms - 1 temperature and initial composition effects, Atmos. Environ., 26A, 625-641. (1992)... 

Explain the role of nitrogen dioxide and nitrate radicals in photochemical smog reaction during daytime and nighttime. 

Photochemical smog Reactions in the lower troposphere caused by emissions such as NO, gases and hydrocarbons from automotive exhaust (Theodore and Theodore 1996)... 

Aldehydes, both aliphatic and aromatic, are powerful air pollutants. They are present in exhaust gas and are also formed from exhaust gas in smog-forming reactions in the air. They have been reported to be eye irritants and irritants to mucous membranes, plant toxicants, and participants in photochemical smog reactions. 

Studies by General Motors Research (20) and Midwest Research Institute (21) have shown that lead compounds in car exhaust do not contribute to or enter into photochemical smog reactions. 

Atomic oxygen can also react with hydrocarbons to form other chemicals that are toxic and also impart an odor to the air. On a sunny day only about 0.2 ppm of nitrogen oxides and 1 ppm of reactive hydrocarbons are sufficient to initiate these photochemical smog reactions. The hydrocarbons involved in these reactions come mostly from unburned petroleum products such as gasoline, and the nitrogen oxides come from the exhausts of internal combustion engines. 

Note that non-acidic sulfate aerosols are produced from sea spray and crustal materials these compounds tend to have larger particle sizes than the typically acidic particles. With the exception of primary emissions of acids, the transformation processes are just as important as the source terms both are needed to produce acid aerosols. Reactions in the aqueous phase (fog) are much faster than in the gas phase and can produce acids on a local scale. The slower gas-phase reactions tend to produce acids on a larger scale, often regional in extent. Organic acids are usually the products of photochemical smog reactions. 

The important hydrocarbon classes are alkanes, alkenes, aromatics, and oxygenates. The first three classes are generally released to the atmosphere, whereas the fourth class, the oxygenates, is generally formed in the atmosphere. Propene will be used to illustrate the types of reactions that take place with alkenes. Propene reactions are initiated by a chemical reaction of OH or O3 with the carbon-carbon double bond. The chemical steps that follow result in the formation of free radicals of several different types which can undergo reaction with O2, NO, SO2, and NO2 to promote the formation of photochemical smog products. 

Photochemical smog Air conditioning/ventilation units Reaction between chemicals and ozone... 

Combustion processes are the most important source of air pollutants. Normal products of complete combustion of fossil fuel, e.g. coal, oil or natural gas, are carbon dioxide, water vapour and nitrogen. However, traces of sulphur and incomplete combustion result in emissions of carbon monoxide, sulphur oxides, oxides of nitrogen, unburned hydrocarbons and particulates. These are primary pollutants . Some may take part in reactions in the atmosphere producing secondary pollutants , e.g. photochemical smogs and acid mists. Escaping gas, or vapour, may... 

Consider the air pollutants NO and N02, contributors to photochemical smog. Both can be formed by the reaction between atmospheric nitrogen and oxygen. At 25°C,... 

Photochemical smog is formed, in part, by the action of light on nitrogen dioxide. The wavelength of the radiation absorbed by N02 in this reaction is 197 nm. 

The atmospheric chemistry of nitrogen is quite complex and involves literally hundreds or thousands of chemical reactions. Although the fluxes are much smaller than the biological fluxes, these processes are important for a variety of reasons, including impacts on climate, stratospheric ozone, and photochemical smog. In this section we present an overview of the most important processes. 

These reactions are important in a cycle that oxidizes CO and hydrocarbons and produces ozone, in the presence of NO (NO + N02). In photochemical smog, ozone can build up to... 

C05-0120. Explain in your own words how the reactions occurring in the cylinders of automobile engines contribute to the production of photochemical smog. Use balanced equations when appropriate. 

A reaction of ozone provides an example of concentration effects. Ozone in the atmosphere near the Earth s surface is a serious pollutant that damages soft tissues such as the lungs. In major urban areas, smog alerts are issued whenever there are elevated concentrations of ozone in the lower atmosphere. Nitmgen oxide, another component of photochemical smog, is a colorless gas produced in a side reaction in automobile engines. One reaction that links these species is the reaction of NO and O3 to produce O2 and NO2 ... 

C16-0125. One reaction that plays a role in photochemical smog is the following ... 

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