Contaminant Fate and Transport - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 294

(km)

(mi)

0.0001

100

Thermosphere

60

0.001

90

Mesopause

50

80

0.01

70

0.1 40

Mesosphere

60

50

30

1

Stratopause

40

Ozone region

20

10 30

Stratosphere

20

10

100

Mt. Eeverest
8848m

Tropopause

10

Troposphere

1000

180 200 220 240 260 280 300

Temperature (K)

FIGURE 8.13
Layers of the atmosphere. (From United States Standard Atmosphere, The Standard Atmosphere of the United
States , National Oceanic and Atmospheric Administration, National Aeronautics and Space Administration,
and the United States Air Force, Washington, DC: United States Government Printing Office, 1976.)

Advective transport
of smoke by wind
and dispersion

Rising smoke due to
advective convection

Billowing smoke
indicative of
turbulent diffusion

FIGURE 8.14
Smoke rising into the atmosphere from a fire. (Photo
by Daniel T. Rogers.)

Anthropogenic sources of atmospheric contaminants are significant and present
themselves as an array of different contaminants released in high volumes annually
(USEPA 1998a). Most contaminants are released into the atmosphere from anthropo-
genic sources at or near the surface, with most of the impacts occurring in the tropo-
sphere, and to a lesser degree, the stratosphere (USEPA 1991). Contaminants released
near the ground surface can mix throughout the troposphere in a few weeks, but it
can take years or decades for them to reach the stratosphere (Hemond and Fechner-
Levy 2000). Records of atmospheric contaminants and their effects can be traced to the