Encyclopedia of Environmental Science and Engineering, Volume I and II

Part 1. Pollutant Emissions (continued)

Pollutant types Sources and abundance Abatement and control

CO 2 is not typically considered a pollutant in air

pollution regulations, however, its role in the

global heat balance is well recognized. CO 2 can

heat up the earth’s surface by a phenomenon

commonly called the “greenhouse effect.” This

“greenhouse effect” is caused primarily by water

vapor and CO 2 , both of which are strong

absorbers of infrared radiation. When radiation is

absorbed by CO 2 and water, it is reemitted in all

directions with the net result being that part of the

radiation returns to the earth’s surface and raises

the temperature. Since 1890, atmospheric CO 2

levels have increased from about 290 to 322 ppm.

25% of this increase has occurred in the past

decade. Since 1958, the atmospheric CO 2 levels

have increased at a rate of approximately 0.7 ppm

per year. If this trend continues, atmospheric CO 2

levels could double by the year 2035a.d. This

doubling could result in the warming of surface

temperatures by 2.4ºC in the midlatitudes, with a

greater warming in the polar regions.

Sulfur Oxides

a. Sulfur Dioxide:

Sulfur dioxide (SO 2 ) is a colorless gas whose odor

and taste can be detected in the concentration

range of 0.3 to 0.1 ppm. Above 3 ppm, it has a

pungent, irritating odor. Although SO 2 emissions

may occur from volcanic eruptions, most SO 2

(and sulfur trioxide, SO 3 ) is due to the burning of

In order to reduce the levels of

sulfuric acid aerosols in urban

air, power plants are often built

with tall smokestacks which

disperse the SO 2 over a wide area.

This reduces the local problem but

increases the problem for areas

(continued)

25

20

15

10

5

0

1950 1955 1960 1965 1970 1975 1980 1985

Year

Short tons per capita

United States

Canada

Global

Mexico

FIGURE 2 Comparison of Per Capita Carbon Dioxide emissions.

Note(s): U.S. per capita emissions data is not presented for 1990 or 1991. See section 10.1 for a discussion of

1990 to 1994 national CO 2 emission estimates.

Sources(s): Marland, G., R.J. Andres, and T.A. Boden 1994. Global, regional and national CO 2 emissions, pp.

9–88. In T.A. Boden, D.P. Kaiser, R.J. Sepanski, and F.W. Stoss (Eds.), Trends ’ 93: A Compendium

of Data on Global Change. ORNL/CDIAC-65. Carbon Dioxide Information Analysis Center, Oak

Ridge National Laboratory, Oak Ridge, Tenn., U.S.A.

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