Page 53 - Fundamentals of Air Pollution

IV. Concepts 29

Fig. 2-3. Grand average number (N), surface area (S), and volume (V) distribution of
Los Angeles smog. The linear ordinate normalized by total number (NT), area (ST), or volume
(VT) is used so that the apparent area under the curves is proportional to the quantity in that
size range. Source: Corn, M, Properties of non-viable particles in the air, In "Air Pollution/'
3rd ed., Vol. I ( A. C. Stern, ed.). Academic Press, New York, 1976, p. 123.

each element or radical, anion, or cation is present in the mixture can be
determined. Specific organic compounds may be separated and identified.
Individual particles may be analyzed by electron microscopy techniques.
Much of the concern about particulate matter in the atmosphere arises
because particles of certain size ranges can be inhaled and retained by the
human respiratory system. There is also concern because particulate matter
in the atmosphere absorbs and scatters incoming solar radiation. For a
detailed discussion of the human respiratory system and the defenses it
provides against exposure of the lungs to particulate matter, see Chap-
ter 7.

IV. CONCEPTS

A. Sources and Sinks
The places from which pollutants emanate are called sources. There are
natural as well as anthropogenic sources of the permanent gases considered
to be pollutants. These include plant and animal respiration and the decay
of what was once living matter. Volcanoes and naturally caused forest fires
are other natural sources. The places to which pollutants disappear from
the air are called sinks. Sinks include the soil, vegetation, structures, and
water bodies, particularly the oceans. The mechanisms whereby pollutants