Environmental Engineering Reference
In-Depth Information
Figure 3.2. In summary, incoming radiation can be absorbed (in the atmosphere and at
the surface),
Table 3.2 Albedos for the short-wave part of the
spectrum
Surface
Albedo (%)
Water (zenith angles above 40°)
2-4
Water (angles less than 40°)
6-80
Fresh snow
75-90
Old snow
40-70
Dry sand
35-45
Dark, wet soil
5-15
Dry concrete
17-27
Black road surface
5-10
Grass
20-30
Deciduous forest
10-20
Coniferous forest
5-15
Crops
15-25
Tundra
15-20
OZONE
human impact
Ozone is a rare gas made up of three atoms of oxygen. Its concentration rarely exceeds a
few parts per billion and yet it is a vital component of our atmosphere. In the stratosphere
it is formed through the interaction of the shorter, ultra-violet part of the sun's radiation
and the oxygen molecules, which consist of two atoms of oxygen. The reaction for ozone
formation is:
The result is the almost total exclusion of the harmful part of the ultra-violet rays of
the sun.
In the troposphere ozone exists as a by-product of photochemical processes between
sunlight and pollutants, particularly nitrogen oxides from car exhausts. It is considered
toxic above sixty parts per billion and has harmful effects on plant growth as well as
causing respiratory problems. In the lower part of the atmosphere its concentration has
been increasing as a result of higher car pollution, but in the stratosphere its level should
remain constant, destruction being balanced by creation.
However, in 1985 scientists working in Antarctica announced that ozone levels in the
southern hemisphere stratosphere had fallen by 40 per cent between 1977 and 1984. In
the Antarctic spring (October) a hole the size of the United States and about 10 km deep
