Geoscience Reference
In-Depth Information
real scales of danger threatening the life on the Earth can be estimated only with the
use of the global model of the nature-society system.
A diversity of the anthropogenic impacts on the global biogeochemical cycle of
oxygen is determined by direct and indirect causes of breaking the natural balance
of oxygen. According to the equation of photosynthesis, the gram-molecular
amounts of assimilated CO
2
and emitted O
2
are equal. Also equal are the gram-
molecular amounts of assimilated O
2
and emitted CO
2
for the dead organic matter
decomposition and fuel burning. Hence, for time periods of tens and hundreds of
years, a change of the CO
2
amount in the atmosphere is accompanied by the same
change of O
2
, but in the opposite direction. For instance, a CO
2
doubling in the
atmosphere leads to a decrease of the amount of O
2
. But, since the volume con-
centration of CO
2
in the atmosphere is now estimated at 0.031 %, and that of O
2
at
20.946 %, in this case a decrease of O
2
will constitute only 0.15 % of the total O
2
content in the atmosphere.
Imagine the following situation. Let
the total biomass of
the biosphere
10
11
t C), and all fossil chemical
fuel, the explored supplies of which constitute 128
10
11
t C), all organic matter of soil (
(
*
9.6
×
*
14
×
10
11
×
t of conditional fuel
10
11
t C) be burnt. Then the amount of CO
2
in the atmosphere increases by a
factor of 12.5, and that of O
2
, respectively, decreases but only by 1.75 %. Hence, the
amount of oxygen during hundreds of years has to be practically constant.
However, it should be borne in mind that the region of excess anthropogenic
emissions of CO
2
and, hence, O
2
assimilation is concentrated on a small area of
cities and forest
(64
×
fires. Since the concentrations in the atmosphere do not equalize
instantly, a gradient of O
2
concentrations can appear around these sites, when the
oxygen provision will be insuf
cient for animals and humans. Therefore the model
of the global oxygen cycle (MGBO unit) re
ecting the spatial heterogeneities in the
distributions of O
2
concentrations, enables one to reveal such dangerous territories.
An interaction between the cycles of oxygen, nitrogen, sulfur, phosphorus, and
carbon manifests itself through the processes of oxidation and decomposition. The
level of detailing the global model units does not permit one to re
fl
ect all the diversity
of these processes. Therefore in the simplest case, when only averaged characteristics
of the oxygen cycle elements are taken into account, the scheme in Fig.
1.38
of the
global O
2
fl
fl
fluxes can be presented as the schemes in Figs.
1.36
and
1.37
. The indicated
stability of the O
2
concentration in the atmosphere makes it possible to simplify a
description of the MGBO unit, using a single balance equation:
@
O
@
t
þ
V
u
@
O
@u
þ
V
k
@
O
@k
¼ k
0
R
F
þ
k
L
R
L
m
L
T
L
b
G
G
m
F
T
F
m
G
T
G
l
Q
R
Q
where k
0
and k
L
are the indicators of the rate of O
2
emission due to photosynthesis
in the ocean and on land, respectively,
ʽ
s
is the indicator of the role of respiration of
land vegetation (s=L), animals (s=F), and humans (s=G) in the removal of
oxygen from the atmosphere,
ʼ
Q
is the rate of O
2
consumption at the decomposition
of the soil dead organic matter.
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