Geoscience Reference
In-Depth Information
Table 1.8 Greenhouse gases and global warming potentials (GWPs)
Gas
100 year
GWP
ʔ
GWP
(%)
Gas
100 year
GWP
ʔ
GWP
(%)
Carbon dioxide (CO
2
)
1
55
HFC-227ea (C
3
HF
7
)
2,900
0.69
Methane (CH
4
)
21
17
HFC-236fa (C
3
H
2
F
6
)
6,300
0.75
Nitrous oxide (N
2
O)
310
5
HFC-43-10mee (C
5
H
2
F
10
)
1,300
0.75
HFC-23 (CHF
3
)
11,700
0.96
Per
fl
uoromethane (CF
4
)
6,500
1.15
HFC-125 (C
2
HF
5
)
2,800
0.75
Perfluoroethane (C
2
F
6
)
9,200
0.75
HFC-134a (CH
2
FCF
3
)
1,300
0.34
Perfluorobutane (C
4
F
10
)
7,000
0.87
HFC-143a (CF
3
CH
3
)
3,800
0.75
Per
fl
uorohexane (C
6
F
14
)
7,400
0.75
HFC-152a (CH
3
CHF
2
)
140
0.28
Sulphur hexafluoride (SF
6
)
23,900
0.3
biogenic, and biological cycles of this rotation. The biogenic cycle includes sub-
cycles, such as biogeochemical, biogeocenotic, and geochemical.
Land ecosystems play an important role in the biogeochemical cycles
dynamics
on Earth. The anthropogenic changes in vegetation covers affect the biogeochemical
cycles and, thereby, other processes, climate included. The most well-known and
important biogeochemical cycles, for example, include cycles of carbon, nitrogen,
oxygen, phosphorus, and water. Biogeochemical cycles always involve equilibrium
states: a balance in the cycling of the element between land surface compartments.
Chemical elements participate in the processes of photosynthesis and respiration of
plants, as well as their dying-off, through which their exchange is formed between
compartments and elements of land ecosystems. The most characteristic features of
biogeochemical cycles of individual chemical elements are as follows:
'
The nitrogen cycle is a much more complicated biogeochemical cycle but also
cycles through living parts and nonliving parts including the water, land, and air.
Nitrogen is a very important element in that it is part of both proteins, present in
the composition of the amino acids that make up proteins, as well as nucleic
acids such as DNA and RNA, present in nitrogenous bases. The largest reservoir
of nitrogen is the atmosphere, in which about 78 % of nitrogen is contained as
nitrogen gas (N
2
). Nitrogen gas is
“
xed,
”
in a process called nitrogen
fixation.
Nitrogen
fixation combines nitrogen with oxygen to create nitrates (NO
3
).
The oxygen cycle is the biogeochemical cycle that describes the movement of
oxygen within and between its three main reservoirs: the atmosphere, the bio-
sphere, and the lithosphere. The main driving factor of the oxygen cycle is
photosynthesis, which is responsible for the modern Earth
'
is atmosphere and life.
The carbon cycle is the biogeochemical cycle by which carbon is exchanged
between the biosphere, geosphere, hydrosphere, and atmosphere of the Earth.
The cycle is usually thought of as four major reservoirs of carbon interconnected
by pathways of exchange. The reservoirs are the atmosphere, the terrestrial
biosphere (which usually includes freshwater systems and non-living organic
material, such as soil carbon), the oceans, and the sediments.
The phosphorus cycle is the biogeochemical cycle that describes the movement
of phosphorus through the lithosphere, hydrosphere, and biosphere. Unlike
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