Geology Reference
In-Depth Information
CHAPTER 2
Chemistry of the Atmosphere
PAUL S. MONKS
Department of Chemistry, University of Leicester, LE1 7RH, Leicester, UK
2.1 INTRODUCTION
The thin gaseous envelope that surrounds our planet is integral to the
maintenance of life on earth. The composition of the atmosphere is
predominately determined by biological processes acting in concert with
physical and chemical change. Though the concentrations of the major
atmospheric constituents oxygen and nitrogen remain the same, the
concentration of trace species, which are key to many atmospheric
processes are changing. It is becoming apparent that man's activities
are beginning to change the composition of the atmosphere over a range
of scales, leading to, for example, increased acid deposition, local and
regional ozone episodes, stratospheric ozone loss and potentially climate
change. In this chapter, we will look at the fundamental chemistry of the
atmosphere derived from observations and their rationalisation.
In order to understand the chemistry of the atmosphere we need to be
able to map the different regions of the atmosphere. The atmosphere can
be conveniently classified into a number of different regions which are
distinguished by different characteristics of the dynamical motions of
the air (see Figure 1). The lowest region, from the earth's surface to the
tropopause at a height of 10-15 km, is termed the troposphere. The
troposphere is the region of the active weather systems which determine
the climate at the surface of the earth. The part of the troposphere at the
earth's surface, the planetary boundary layer, is that which is influenced
on a daily basis by the underlying surface.
Above the troposphere lies the stratosphere, a quiescent region of the
atmosphere where vertical transport of material is slow and radiative
transfer of energy dominates. In this region lies the ozone layer which
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