Environmental Engineering Reference
In-Depth Information
Table 2.1
Average gaseous composition of dry air in
the troposphere
ensures that they are evenly distributed. There is
no evidence that the relative levels of oxygen and
nitrogen are changing significantly, although
there have been measurable changes in the
proportions of other gases in the atmosphere.
Changes in the nature of oxygen, however, are
involved in the depletion of the ozone layer, now
recognised as one of the world's major
environmental issues. Oxygen can exist in the
atmosphere as atomic, diatomic or triatomic
oxygen, depending upon the number of atoms in
a molecule. The most common form is diatomic
oxygen (O
2
), but the triatomic form called ozone
(O
3
), created through the combination of the
other two types, is present in the upper
atmosphere. Ozone is also found close to the
Figure 2.1
S pectral distribution of solar and terrestrial radiation. Solar radiation is represented by a curve for
a black body at 6000°K and terrestrial by a black body at 300°K. A black body is a perfect radiator or
absorber of energy
