Geoscience Reference
In-Depth Information
ux H
1
The
fl
can be, to some extent, interpreted as a compensation for the
fl
uxes
H
13
and H
21
.
The nitrogen supplies on land consist of the assimilable nitrogen in soil
N
S2
≈
10
4
tkm
−
2
, in plants (12
10
9
t), and living organisms (0.2
10
9
t). A
0.19
×
×
×
diversity of nitrogen
fl
fluxes is formed here of the processes of nitrifucation, deni-
tri
uxes
depend on climatic conditions, temperature regime, moistening, as well as chemical
and physical properties of soil. Many qualitative and quantitative characteristics of
these dependences have been described in the literature (Hellebrand et al. 2003).
Let us consider some of them.
Nitri
cation, ammoni
cation,
fixation, and river run-off. The intensities of these
fl
cation is the biological oxidation of ammonia with oxygen into nitrite
followed by the oxidation of these nitrites into nitrates. Nitri
cation is an important
step in the nitrogen cycle in soil. Nitri
cation involves the oxidation of nitrogen by
specialized bacteria (Nitrosomonas, Nitrobacter, etc.). The return of nitrogen to the
cycle due to living micro-organisms is one of the stabilizing natural processes.
Simplifying the whole process of the transformation of ammonia salts into nitrates,
present the activity of heterotrophic micro-organisms and saprophags as a gen-
eralized process of the organic matter decomposition. The rate of the organic matter
decomposition and nitri
cation increases with an increasing temperature, reaching
its optimal value at T
a
= 34.5
ux H
3
°
C. Therefore for the
fl
an approximation
H
3
¼
k
N
j
M
j
can be assumed, where M
ʺ
is the rate of the dying-off of the com-
ponent
ʺ
,
ʻ
N
ʺ
is the content of nitrogen in the component
ʺ
.
Denitri
cation process exists in anoxic environments when nitrate and nitrite act
as
electron acceptors
(oxidizers)
and the nitri
cation reactions
reverse:
cation H
7
on land are important
channels of the input of nitrogen into the atmosphere. The intensity of these pro-
cesses depends on temperature, humidity, pollution of soils with poisonous
chemicals, and pH. The quantitative and functional characteristics of these de-
pendences have been well studied. Within the global model it is possible to take
into account only the factors of temperature and humidity:
NO
3
)
NO
2
)
NO. The processes of denitri
N
S
k
1
þ
N
S
;
H
7
¼
k
6
h
D
2
W
S
where W
S
is soil moisture,
ʸ
2
is the temperature coef
cient,
ʻ
6
and k
1
are empirical
318 t/km
2
parameters. If we assume H
7
¼ 0
ʻ
6
= 0.496, k
1
= 0.556.
In the biological cycle of nitrogen of importance are the processes of its
:
=
year, then
fixation,
10
6
t year
−
1
.
by microorganisms and plants whose intensity is estimated at 148
×
The rate of
fixation, depending on the character of the medium, can vary reaching
10
9
t year
−
1
in highly productive regions. The nitrogen
×
ux H
10
depends on the
3
fl
distribution of vegetation cover
and can be described by the equation
H
10
¼
r
j
k
j
R
j
=r
ij
, where
˃
ʺ
is the area under vegetation of the
ʺ
type on the
territory
Ξ
ij
of the area
˃
ij
, R
ʺ
is the productivity of plants of the
ʺ
type,
ʻ
ʺ
is the
coef
cient.
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