Geoscience Reference
In-Depth Information
methane in the atmosphere is estimated at about 5 years. Its extraction from the
atmosphere takes place due to the participation of methane in photochemical
reactions, resulting in methane oxidation
rst to CO, and then to CO
2
. The cycle
CO
OH
CP
4
plays an important role in the cycle of methane:
-
-
OH + CH
4
!
CH
3
þ
H
2
O
;
OH
þ
CO
!
CO
2
þ
H
The participating OH-radicals form in the atmosphere during the water vapor
photolysis. As a result, atmospheric methane is oxidized.
Methane
13) are functions of temperature, microbial population,
geographical coordinates and other environmental characteristics that are speci
fl
uxes C
i
(i =1
-
c
for pixels
Ξ
ij
. For example, Panikov and Dedysh (2000) developed the model for
methane emission to the atmosphere from snow-covered bogs in West Siberia. This
approach can be used for the modeling of anaerobic formation of CH
4
in pixels with
the permafrost. In this case
fl
ux C
8
can be described by the equation:
dC
8
=
dt ¼
l
X 1
Y
ð
Þ=
Y
;
where
c growth rate of respective microbial population with biomass X,
Y is biomass yield per unit of substrate consumed. Microbial biomass X is formed
with the following law:
ʼ
is speci
dX
=
dt ¼
l
X
;
where
ʼ
max
SR/(S + K
S
), S is catabolic substrate concentration, R is the function
of physiological state, K
S
is saturation constant, numerically equal to that substrate
concentration at which microbial speci
ʼ
=
c growth rate attains the half of maximal
value (
ʼ
max
).
Natural wetlands and rice paddies deliver to the atmosphere more 30 % of global
CH
4
emission. Flux C
3
can be parameterized by the following equation:
C
3
¼ H
r
f
1
T
ð
f
2
ðÞ
f
3
p
ð
f
4
r
p
;
ʼ
= 0.5
where H
r
is heterotrophic respiration, T
s
is soil
temperature, h is water table
position, r
p
is redox potential, functions fi
i
(i=1
4) parameterized the CH
4
emission
rates. Fluxes C
1
and C
2
that characterize major atmospheric CH
4
sinks are mainly
parameterized by its reaction with hydroxyl (OH) radical. These fluxes depend on
the OH levels and reaction rate. Under this, it is known that increase in methane
leads to positive feedback (Xu et al. 2007; Krapivin and Varotsos 2008).
The human interference into the processes described by this diagram breaks the
natural stability of the balance CH
4
/CO/CO
2
. In particular, the reclaiming of marshes
is one of such destabilizing factors. For instance, the drainage of 20%of marshes leads
o a natural reduction of CH
4
emissions from the marshes by 20 %, and on the whole,
the amount of methane is reduced by 4 %, which practically does not in
-
uence
climate, but causes changes in the biogeochemical cycles of ozone and carbon dioxide
fl
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