Page 41 - Fundamentals of Air Pollution

20 2. The Natural versus Polluted Atmosphere

Fig. 2-1. The regions of the atmosphere.

moon or the planets, and they are regions in which satellites travel in the
earth's orbit. These regions are of interest to communications scientists
because of their influence on radio communications, and they are of interest
to air pollution scientists primarily because of their absorption and scatter-
ing of solar energy, which influence the amount and spectral distribution
of solar energy and cosmic rays reaching the stratosphere and troposphere.
The stratosphere is of interest to aeronautical scientists because it is
traversed by airplanes; to communications scientists because of radio and
television communications; and to air pollution scientists because global
transport of pollution, particularly the debris of aboveground atomic bomb
tests and volcanic eruptions, occurs in this region and because absorption
and scattering of solar energy also occur there. The lower portion of this
region contains the stratospheric ozone layer, which absorbs harmful ultra-
violet (UV) solar radiation. Global change scientists are interested in modi-
fications of this layer by long-term accumulation of chlorofluorocarbons
(CFCs) and other gases released at the earth's surface or by high-altitude
aircraft.
The troposphere is the region in which we live and is the primary focus
of this book.

II. UNPOLLUTED AIR

The gaseous composition of unpolluted tropospheric air is given in Table
2-1. Unpolluted air is a concept, i.e., what the composition of the air would
be if humans and their works were not on earth. We will never know the