199
to lakes became necessary in the 1970s. This procedure was successful in Sweden, Canada and
Norway: planktons, aquatic insects and then fish
regenerated in the treated lakes unless they perished completely before.
For impeding acidification of the environment
international cooperation is required. It became
apparent when severe environmental damage
caused by acidification was recognised that the
sources of trouble are located generally far away
from the places of damage. A classic example is
the acidification of lakes is Sweden that was
caused primarily by emission from industrial
regions in England and Germany. Convention on
Long-range Transboundary Air Pollution was
accepted in Geneva in 1979, signed by representatives of 35 countries, including all European
and North American countries as well. Ratifying
the convention, however, was slow: it was
integrated in the legislation of 24 countries until
1983 and then 30 countries and the European
Community by 1985. The convention targeted
not only the reduction of SO 2 and NO x emission
but that of other air pollutants as well (hydrocarbons, heavy metals, solid particles). Separate
reports were made regarding each pollutants.
4.5.4 Present and Future
of the Ozone Shield
Ozone—oxygen molecule with three atoms—
can be found in the atmosphere in very small
quantity (even less than one millionth part of
gases); however, it is essential regarding the protection of life. It can be found in much greater
concentration than usual at a height of 15–50 km
in the stratosphere and absorbs that part of the
ultra violet (UV) radiation arriving from the Sun
which threatens life on Earth (UV-C radiation:
200–290 nm, UV-B radiation: 290–320 nm)
either completely or partially. (Layer of the atmosphere with greatest ozone content is located at a
height of 20–30 km.)
UV radiation in great dose damages many living organisms and also influences unfavourably
the photosynthesis and other physiological features of plants while it has tumorigenic effects
(primarily epithelioma), damages the immune
system and could cause eye diseases as well. It is
also dangerous to planktons living near surface
layers of the sea.
Due to its protective effect stratospheric ozone
layer is also referred to as ozone shield which is
not an accurate term because a part of UV radiation can get through it and reaches the Earth’s
surface. Atmospheric concentration of ozone is
given in Dobson unit (DU). One DU expresses
the ozone quantity which would form a 0.01 mm
thick layer in surface temperature and pressure
conditions. Multi-year average of stratospheric
ozone is 300 DU that would form a layer of 3 mm
on the surface. The average concentration of
ozone varies depending on geographical latitude:
260–280 DU above tropical areas, 380–400 DU
above latitude 60. Concentration of stratospheric
ozone undulates greatly in natural conditions as
well (daily and annual rhythms and irregular
changes are typical); therefore, it is not easy to
clearly separate natural and anthropogenic
changes.
Increasing degree of ozone concentration
decrease was measured above the Antarctic from
the 1970s.
The term “ozone hole” is used if the concentration of ozone falls below 220 DU even though
the term is even less apt than ozone shield as
“ozone hole” still reduces UV radiation, i.e. it
cannot cross it without hindrance. Furthermore,
the existence of the hole is periodical, occasionally the “hole darns itself”. It would be more correct to talk about ozone thinning, but the
resounding term already came into general use in
the literature. Above the Antarctic stratospheric
ozone concentration generally decreases gradually at the end of August and in September, then
the low level stabilises in October (at the start of
Antarctic spring) and then it starts to increase
again in November and slowly returns near the
multi-year average value. The reason for ozone
thinning was initially searched in nitrogen oxides
emitted by air transport but measurement results
shifted the focus of scientists to freons (Crutzen
1970).
Shortly later Molina and Rowland (1974)
proved that halogenated hydrocarbons are
4.5 Changes in the Atmosphere Owing to Human Impacts and Their Consequences
to lakes became necessary in the 1970s. This procedure was successful in Sweden, Canada and
Norway: planktons, aquatic insects and then fish
regenerated in the treated lakes unless they perished completely before.
For impeding acidification of the environment
international cooperation is required. It became
apparent when severe environmental damage
caused by acidification was recognised that the
sources of trouble are located generally far away
from the places of damage. A classic example is
the acidification of lakes is Sweden that was
caused primarily by emission from industrial
regions in England and Germany. Convention on
Long-range Transboundary Air Pollution was
accepted in Geneva in 1979, signed by representatives of 35 countries, including all European
and North American countries as well. Ratifying
the convention, however, was slow: it was
integrated in the legislation of 24 countries until
1983 and then 30 countries and the European
Community by 1985. The convention targeted
not only the reduction of SO 2 and NO x emission
but that of other air pollutants as well (hydrocarbons, heavy metals, solid particles). Separate
reports were made regarding each pollutants.
4.5.4 Present and Future
of the Ozone Shield
Ozone—oxygen molecule with three atoms—
can be found in the atmosphere in very small
quantity (even less than one millionth part of
gases); however, it is essential regarding the protection of life. It can be found in much greater
concentration than usual at a height of 15–50 km
in the stratosphere and absorbs that part of the
ultra violet (UV) radiation arriving from the Sun
which threatens life on Earth (UV-C radiation:
200–290 nm, UV-B radiation: 290–320 nm)
either completely or partially. (Layer of the atmosphere with greatest ozone content is located at a
height of 20–30 km.)
UV radiation in great dose damages many living organisms and also influences unfavourably
the photosynthesis and other physiological features of plants while it has tumorigenic effects
(primarily epithelioma), damages the immune
system and could cause eye diseases as well. It is
also dangerous to planktons living near surface
layers of the sea.
Due to its protective effect stratospheric ozone
layer is also referred to as ozone shield which is
not an accurate term because a part of UV radiation can get through it and reaches the Earth’s
surface. Atmospheric concentration of ozone is
given in Dobson unit (DU). One DU expresses
the ozone quantity which would form a 0.01 mm
thick layer in surface temperature and pressure
conditions. Multi-year average of stratospheric
ozone is 300 DU that would form a layer of 3 mm
on the surface. The average concentration of
ozone varies depending on geographical latitude:
260–280 DU above tropical areas, 380–400 DU
above latitude 60. Concentration of stratospheric
ozone undulates greatly in natural conditions as
well (daily and annual rhythms and irregular
changes are typical); therefore, it is not easy to
clearly separate natural and anthropogenic
changes.
Increasing degree of ozone concentration
decrease was measured above the Antarctic from
the 1970s.
The term “ozone hole” is used if the concentration of ozone falls below 220 DU even though
the term is even less apt than ozone shield as
“ozone hole” still reduces UV radiation, i.e. it
cannot cross it without hindrance. Furthermore,
the existence of the hole is periodical, occasionally the “hole darns itself”. It would be more correct to talk about ozone thinning, but the
resounding term already came into general use in
the literature. Above the Antarctic stratospheric
ozone concentration generally decreases gradually at the end of August and in September, then
the low level stabilises in October (at the start of
Antarctic spring) and then it starts to increase
again in November and slowly returns near the
multi-year average value. The reason for ozone
thinning was initially searched in nitrogen oxides
emitted by air transport but measurement results
shifted the focus of scientists to freons (Crutzen
1970).
Shortly later Molina and Rowland (1974)
proved that halogenated hydrocarbons are
4.5 Changes in the Atmosphere Owing to Human Impacts and Their Consequences