Visualizing Environmental Science

200 CHAPTER 8 Air and Air Pollution

Miscellaneous

10%

Transportation

57%

Industrial

processes

12%

Fuel

combustion

(electric power

plants)

21%

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Emory Kristof/NG Image Collection

© Stefan Jannides/

redbrickstock.com/Alamy

a. Transportation and industrial fuel combustion (such as

electric power plants) are major contributors of pollutants.

c. Mobile source of air pollution. Diesel trucks produce particulate matter

and other kinds of air pollution.

b. Stationary source of air pollution. Ash, nitrogen oxides,

sulfur oxides, and hazardous air pollutants are released from

smokestacks at this coal-fired electric power plant in Tennessee.

The combustion of fossil fuels, especially coal, is respon-

sible for most of these emissions. The top three industrial

sources of toxic air pollutants are the chemical industry,

the metals industry, and the paper industry.

Around the world, burning forests to allow crop plant-

ing and burning the remains of a previous year’s crops cre-

ates large amounts of smoke. In Southeast Asia, smoke from

agricultural fires can be thick enough to reduce visibility to

a few meters, even far from where the burning occurs.

1. What is the difference between primary and
   secondary air pollutants?


2. What are the seven main classes of air
   pollutants, and what are some of their sources
   and effects?

The two main human sources of primary air pollut-

ants are transportation (mobile sources) and power plants

(stationary sources) (Figure 8.8a). Cars, trucks, tractors,

and heavy construction equipment are known as mobile

sources. They release significant quantities of nitrogen ox-

ides, carbon oxides, particulate matter, and hydrocarbons

during the combustion of gasoline or diesel fuel. While

diesel engines in trucks, buses, trains, and ships consume

less fuel than other types of combustion engines, they pro-

duce more air pollution (Figure 8.8b). One heavy-duty

truck emits as much particulate matter as 150 automo-

biles, whereas one diesel train engine produces, on aver-

age, 10 times the particulate matter of a diesel truck.

Electric power plants and other industrial facilities,

known as stationary sources, emit most of the particu-

late matter and sulfur oxides released in the United

States; they also emit sizable amounts of nitrogen ox-

ides, hydrocarbons, and carbon oxides (Figure 8.8c).

Sources of primary air pollutants

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