70 Ecology and Applied Environmental Science
Nitrogen cycle perturbation by man and the resulting nitrogen accumulation in the biosphere have the following environmental consequences:
• Eutrophication of aquatic ecosystems in which nitrogen is a limiting
factor (Chapter 8)
• Burdening of aquatic ecosystems (rivers, lakes, oceans, groundwater)
with nitrates or ammonia (Chapter 8)
• Burdening of the atmosphere with nitrogen oxides, which are toxic,
contribute to the creation of acid rain and intensifie the greenhouse
effect (Chapter 9)
The problem, summarily, is that the pace of total nitrogen fixation is
at present significantly greater than the pace of total denitrification.
Therefore, the soil and the waters, at least on a local scale, accumulate each
year a surplus of fixed nitrogen. Dealing with this perturbation requires
the restoration of the nitrogen cycle’s more natural function, i.e. the reduction of industrial fixation, nitrogen oxide emissions in the atmosphere,
and generally, of every kind of anthropogenic nitrogen fixation, as well
as the protection or enforcement of natural and the development of artificial denitrification processes, such as removal of nitrogen from wastewater
by tertiary treatment (Chapter 10), treatment of car air emissions through
catalytic converters (Chapter 10) and creation of artificial wetlands.
4.3.4 oxygen cycle
Oxygen is the most abundant element both in Earth’s crust and in the living
matter; it is present in numerous chemical compounds. Oxygen is necessary to life, since it allows for aerobic respiration to occur but in great
concentrations it can be toxic for organisms; it can also cause spontaneous
ignition of dry vegetation or biomass. Its cycle is complicated and creates
special sectors in the atmosphere, hydrosphere and lithosphere. However,
it is realised for the largest part between the atmosphere and the biosphere,
through photosynthesis which produces O 2 and respiration which consumes
it. Thus it portrays essentially the opposite image of the carbon cycle, since
the movements of the one are executed in the opposite direction of those
of the other. Due to the existence of a large O 2 quantity in the atmosphere,
its total recycling by the ecosystems takes thousands of years.
Atmospheric O 2 as well as O 2 compounds of many surface rocks
( limestone, iron oxides etc.) have a biogenetic origin. O 2 did not exist in
the primitive atmosphere and was produced by the photosynthesis of plants
and other organisms. Excessive O 2 production ceased millions of years ago,
since photosynthesis and total respiration reached an equilibrium, resulting
in the end of O 2 accumulation in the atmosphere.
Nitrogen cycle perturbation by man and the resulting nitrogen accumulation in the biosphere have the following environmental consequences:
• Eutrophication of aquatic ecosystems in which nitrogen is a limiting
factor (Chapter 8)
• Burdening of aquatic ecosystems (rivers, lakes, oceans, groundwater)
with nitrates or ammonia (Chapter 8)
• Burdening of the atmosphere with nitrogen oxides, which are toxic,
contribute to the creation of acid rain and intensifie the greenhouse
effect (Chapter 9)
The problem, summarily, is that the pace of total nitrogen fixation is
at present significantly greater than the pace of total denitrification.
Therefore, the soil and the waters, at least on a local scale, accumulate each
year a surplus of fixed nitrogen. Dealing with this perturbation requires
the restoration of the nitrogen cycle’s more natural function, i.e. the reduction of industrial fixation, nitrogen oxide emissions in the atmosphere,
and generally, of every kind of anthropogenic nitrogen fixation, as well
as the protection or enforcement of natural and the development of artificial denitrification processes, such as removal of nitrogen from wastewater
by tertiary treatment (Chapter 10), treatment of car air emissions through
catalytic converters (Chapter 10) and creation of artificial wetlands.
4.3.4 oxygen cycle
Oxygen is the most abundant element both in Earth’s crust and in the living
matter; it is present in numerous chemical compounds. Oxygen is necessary to life, since it allows for aerobic respiration to occur but in great
concentrations it can be toxic for organisms; it can also cause spontaneous
ignition of dry vegetation or biomass. Its cycle is complicated and creates
special sectors in the atmosphere, hydrosphere and lithosphere. However,
it is realised for the largest part between the atmosphere and the biosphere,
through photosynthesis which produces O 2 and respiration which consumes
it. Thus it portrays essentially the opposite image of the carbon cycle, since
the movements of the one are executed in the opposite direction of those
of the other. Due to the existence of a large O 2 quantity in the atmosphere,
its total recycling by the ecosystems takes thousands of years.
Atmospheric O 2 as well as O 2 compounds of many surface rocks
( limestone, iron oxides etc.) have a biogenetic origin. O 2 did not exist in
the primitive atmosphere and was produced by the photosynthesis of plants
and other organisms. Excessive O 2 production ceased millions of years ago,
since photosynthesis and total respiration reached an equilibrium, resulting
in the end of O 2 accumulation in the atmosphere.