Geoscience Reference
In-Depth Information
The nitrogen supplies in water bodies are replenished due to bacterial decom-
position of organic sediments and dissolved organic matter. Consider the compo-
nent D denoting the content of dead organic matter in the water medium. On its
basis, one can write the following relationship: H 18 ¼ k D D ðu; k;
ʻ D is
the indicator of the nitrogen content and the rate of detritus lysis. The free nitrogen
supplies in the water medium are also replenished in the process of functioning of
various organisms. With account of phytoplankton
z
;
t Þ , where
ʦ
and nekton r, we have:
H 4 ¼ H r þ H N
H r ¼ k r T r ;
H N
U ;
U ¼ k U T U ;
where T r and T ʦ are the characteristics of metabolic processes, respectively, in
nekton and phytoplankton,
ʻ r and
ʻ ʦ are the coef
cients. To determine the averages
194 t km 2 year 1
125 t km 2 year 1
of these coef
cients, assume T r ¼ 0
:
;
T U ¼ 0
:
;
H r ¼ H N
83 10 3 tkm 2 year 1 . Then
U ¼ 0
:
ʻ r = 0.00428,
ʻ ʦ = 0.00664.
cation in the water medium delivers considerable
amounts of nitrogen into the atmosphere: H 20 ¼ k 5 ðh 2 Þ D T N U ðu; k; z ; t Þ , where
The process of denitri
ʻ 5
and
ʸ 2 are the constants.
The biological
fixation of nitrogen in the water medium constitutes about
10 6 tyear 1 , reaching 20.7
10 6 t year 1 in the photic layer of the ocean, and
10
×
×
10 4 tkm 3 year 1 in small lakes. For the World Ocean, H 17 ¼ 0
(36
0277
tkm 2 year 1 , on the average. Assuming H 17 ¼ k R R U , where R ʦ is the phyto-
plankton produce averaging 168.8 t km 2 year 1 , we obtain
1,800)
×
:
-
10 3 .
The characteristic feature of the nitrogen cycle in the water medium is its
transport due to gravitational sedimentation, vertical convection, turbulent diffu-
sion, and convergence. The processes of nitrogen transport by migrating animals
are almost negligible and can be neglected in the global model. The simplest form
of description of
ʻ R = 0.164
×
the vertical
fl
fluxes of nitrogen is reduced to the model
H 14 ¼ k j D
H 15 ¼ k q D
=(P, L, F).
The present contribution of human activity to the general biospheric cycle of
nitrogen has reached a level when the consequences of the introduced changes
become unpredictable and probably rather catastrophic. The epidemiological
studies testify to the growth of respiration diseases on the territories with high
concentrations of nitrogen and sulfur oxides as well as photochemical oxidizers.
The harmful effect of nitrogen oxides on living organisms starts manifesting itself
when the level 940 m kg m 3 is exceeded. In general, the consequences of the
nitrogen pollution of the biosphere are more complicated. For instance, on the one
hand, the technogenic accumulation of nitrogen from the atmosphere at fertilizer
production plays a positive role by raising the productivity of land and water
ecosystems, and on the other hand, it causes an undesirable eutrophication of water
basins. Removal of nitrogen from the atmosphere for industrial and agricultural
needs is compensated for by a technogenic input of nitrogen into the atmosphere
with the burning of solid and liquid fuel. A considerable share is contributed here
by the transport emitting nitrogen oxides reaching, for instance,
N j ;
N q , where
ʺ
=(U, P, L),
ˁ
in the USA,
t year 1 . However, even an observance of this physical equilibrium
10 6
11.7
×
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