125
peratures results in the release of nitrogen oxides
into the atmosphere in vast amount. This is the
case with combustion engines, the energy industry, metal industry and domestic heating using
natural gas as well. From nitrogen oxides in such
processes 30 megatonnes of nitrogen is produced
globally on terrestrial lands via chemical transformation and then dry and wet deposition.
Nitrogen absorption by marine living beings
can be estimated to be around 140 megatonnes
globally with a margin of error of ±50%.
Simplified system model of the nitrogen cycle
can be seen in Fig. 4.40. It is worth noting that
scientist try to incorporate atmospheric chemical
processes in the models in recent years; therefore, the models are turning very complex, however, this is not detailed in the figure for keeping
it relatively simple. The authors consider the
great dispersion of flux data in the literature a
much more important problem. For example,
according to Jaffe (2000), the quantity of nitrogen released into the atmosphere from oceans via
denitrification is 25–180 Tg (=25–180 Mt) while
the same ranges between 10 Tg and 200 Tg
(=10–200 Mt) in biological absorption showing
high variability. Fowler et al. (2013) incorporated
the data of 17 authors analysed nitrogen cycle on
the basis of the most reliable database, according
to current knowledge.
Studying Fig. 4.40 it can be seen that fluxes
are minimal compared to the nitrogen stock of
the atmosphere, thus they cannot influence the
nitrogen content of the atmosphere. Greatest
nitrogen exchange is produced by terrestrial and
marine plants: their joint annual nitrogen fixation
(BNF) exceeds 250 Mt. while annual denitrification is around 200–380 Mt. Uncertainty is caused
by the lack of knowledge regarding denitrification in oceans. Biomass burning releases 40 Mt.
nitrogen into the atmosphere annually in the form
of NO while animal metabolism releases further
60 Mt. in the form of NH 3 . (Cattle breeding has a
significant role in this.) The above two compounds are transformed chemically in the atmosphere and then nitrogen gets back to the surface
of continents and oceans in oxidised and reduced
forms via dry and wet deposition. From continents 80 Mt. of nitrogen are washed into oceans
in the form of dissolved N compounds via rivers
and groundwater flow.
Phosphorus is just as important as nitrogen for
living beings: a fundamental element of DNA
molecules and adenosine triphosphate (ATP)
supplying energy for the cells. Its natural cycle
and significance in the history of Earth have been
studied by numerous scientists (Ruttenberg 2003;
Slomp and Van Cappellen 2006; Filippelli 2008;
Elser and Bennett 2011; Reinhard et al. 2016).
The phosphorus cycle includes a complex
series of transition of organic and inorganic phosphates; therefore, a simplified model is presented
here. The natural cycle is controlled mostly by
biotic processes in which microorganisms have a
decisive role. In the twentieth century with extensive application of fertilisers and other phosphorus containing chemicals humanity takes control
to an increasing grade in the phosphorus cycle.
In terrestrial areas phosphorus is derived from
dead plant remnants supplying the phosphorus
content of soils as it is used continuously by
plants striking root in the soil (Fig. 4.41).
Terrestrial animals obtain phosphorus via food
chains from the plants. Faeces of animals and
their carcass releases organic phosphorus into the
soil where it is mineralised and thus transformed
to be available for plants. In this way a small
phosphorus cycle is formed involving soil, plants
and animals (centre of Fig. 4.41). Bird and bat
faeces have greatest significance regarding animal faeces. Economically valuable guano is
sometimes accumulated in enormous quantity by
bird and bat colonies that is transformed into a
sedimentary rock by bacteria activity. It is mined
presently in several countries as excellent manure
due to its nitrogen and potassium content apart
from phosphorus. Phosphorus also occurs in several minerals, apatite is mined most often. With
the prosperity of fertiliser production in the
twentieth century the application of phosphorus
in cultivation became general thus the inorganic
phosphorus content of soils has been increased
significantly generating better crop yield.
Some terrestrial phosphorus is transported
into lakes and oceans by erosion and rivers supplying in this way the needs of aquatic organism.
In natural conditions phosphorus is often a limit4.2 Changes in the Pedosphere
peratures results in the release of nitrogen oxides
into the atmosphere in vast amount. This is the
case with combustion engines, the energy industry, metal industry and domestic heating using
natural gas as well. From nitrogen oxides in such
processes 30 megatonnes of nitrogen is produced
globally on terrestrial lands via chemical transformation and then dry and wet deposition.
Nitrogen absorption by marine living beings
can be estimated to be around 140 megatonnes
globally with a margin of error of ±50%.
Simplified system model of the nitrogen cycle
can be seen in Fig. 4.40. It is worth noting that
scientist try to incorporate atmospheric chemical
processes in the models in recent years; therefore, the models are turning very complex, however, this is not detailed in the figure for keeping
it relatively simple. The authors consider the
great dispersion of flux data in the literature a
much more important problem. For example,
according to Jaffe (2000), the quantity of nitrogen released into the atmosphere from oceans via
denitrification is 25–180 Tg (=25–180 Mt) while
the same ranges between 10 Tg and 200 Tg
(=10–200 Mt) in biological absorption showing
high variability. Fowler et al. (2013) incorporated
the data of 17 authors analysed nitrogen cycle on
the basis of the most reliable database, according
to current knowledge.
Studying Fig. 4.40 it can be seen that fluxes
are minimal compared to the nitrogen stock of
the atmosphere, thus they cannot influence the
nitrogen content of the atmosphere. Greatest
nitrogen exchange is produced by terrestrial and
marine plants: their joint annual nitrogen fixation
(BNF) exceeds 250 Mt. while annual denitrification is around 200–380 Mt. Uncertainty is caused
by the lack of knowledge regarding denitrification in oceans. Biomass burning releases 40 Mt.
nitrogen into the atmosphere annually in the form
of NO while animal metabolism releases further
60 Mt. in the form of NH 3 . (Cattle breeding has a
significant role in this.) The above two compounds are transformed chemically in the atmosphere and then nitrogen gets back to the surface
of continents and oceans in oxidised and reduced
forms via dry and wet deposition. From continents 80 Mt. of nitrogen are washed into oceans
in the form of dissolved N compounds via rivers
and groundwater flow.
Phosphorus is just as important as nitrogen for
living beings: a fundamental element of DNA
molecules and adenosine triphosphate (ATP)
supplying energy for the cells. Its natural cycle
and significance in the history of Earth have been
studied by numerous scientists (Ruttenberg 2003;
Slomp and Van Cappellen 2006; Filippelli 2008;
Elser and Bennett 2011; Reinhard et al. 2016).
The phosphorus cycle includes a complex
series of transition of organic and inorganic phosphates; therefore, a simplified model is presented
here. The natural cycle is controlled mostly by
biotic processes in which microorganisms have a
decisive role. In the twentieth century with extensive application of fertilisers and other phosphorus containing chemicals humanity takes control
to an increasing grade in the phosphorus cycle.
In terrestrial areas phosphorus is derived from
dead plant remnants supplying the phosphorus
content of soils as it is used continuously by
plants striking root in the soil (Fig. 4.41).
Terrestrial animals obtain phosphorus via food
chains from the plants. Faeces of animals and
their carcass releases organic phosphorus into the
soil where it is mineralised and thus transformed
to be available for plants. In this way a small
phosphorus cycle is formed involving soil, plants
and animals (centre of Fig. 4.41). Bird and bat
faeces have greatest significance regarding animal faeces. Economically valuable guano is
sometimes accumulated in enormous quantity by
bird and bat colonies that is transformed into a
sedimentary rock by bacteria activity. It is mined
presently in several countries as excellent manure
due to its nitrogen and potassium content apart
from phosphorus. Phosphorus also occurs in several minerals, apatite is mined most often. With
the prosperity of fertiliser production in the
twentieth century the application of phosphorus
in cultivation became general thus the inorganic
phosphorus content of soils has been increased
significantly generating better crop yield.
Some terrestrial phosphorus is transported
into lakes and oceans by erosion and rivers supplying in this way the needs of aquatic organism.
In natural conditions phosphorus is often a limit4.2 Changes in the Pedosphere