Selected Topic in Depth Photochemical Smog

Photochemical smog, an infamous example being Los Angeles smog, is a combination of unburned hydrocarbons, carbon monoxide, and nitrogen oxides from automobile exhaust that reacts under the influence of sunlight to produce a variety 

The third primary pollutant is nitric oxide, which, as discussed in Section 16.3, is produced by the reaction of molecular nitrogen and oxygen. [See Equation (16.26) in Table 16.5.] At ordinary air temperatures, this reaction has a very low equilibrium constant, but the value is appreciably higher at the high temperatures of the ICE. 

In summary, then, the primary pollutants from the internal combustion engine of an automobile are carbon monoxide, lower hydrocarbons, and nitric oxide. These are dangerous, toxic materials in themselves but are just the beginning of the story. The action of sunlight on the primary pollutants is what really still makes photochemical smog one of the most difficult problems facing humankind as we begin the twenty-first century. 

For example, oxygen atoms combine with water to produce the very reactive and important hydroxyl radical, OH, as shown in Equation (16.62)  

The hydroxyl radical, in turn, is integral to many atmospheric reactions including those that activate the various lower hydrocarbons to more reactive radical groups. For example, the hydroxyl radical combines with methane to produce the methyl radical (CH3), as shown in Equation (16.63)  

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