Selected Topic in Depth Acid Rain

One two-step reaction sequence representing the role of hydroxyl groups in the oxidization of sulfur dioxide directly to sulfuric acid is shown in Equation (17.29). Alternatively, the SO3H can react with diatomic oxygen and water to produce the acid as shown in Equations (17.30) and (17.31). 

Another S02-to-H2S04 pathway may be initiated by the photodissociation of tropospheric ozone to molecular and atomic oxygen as shown in Equation (17.32). The oxygen atom then reacts with sulfur dioxide to produce the trioade [Equation (17.33)] that in turn combines with water to form the sulfuric acid aerosol. 

The effect of add rain in the United States, 2008. The average pH of rainfall is shown by contour lines. 

In high-altitude areas, such as the Adirondack Mountains of New York, forests are bathed directly in high-acidity clouds, or acidfog. The devastating effects on these forests have been well documented. When acid rain falls in areas with little natural capacity to neutralize it the pH of lakes and ponds has been known to fall to as low as 5.2, and aquatic and plant life have greatly suffered. 

Flue-gas desulfurization (FGD) is the best way to remove sulfur dioxide from fossil fuel power plants. FGD commonly uses either wet or dry scrubbers. In wet scrubbers, a slurry of limestone, CaC03, or hydrated lime Ca(OH)2 is sprayed 

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