Environmental Engineering Reference
In-Depth Information
TABLE 1.1 Global carbon reservoir overview
Pools
Quantity (Gt
a
)
Atmosphere
720
Oceans
38,400
Total inorganic
37,400
Surface layer
670
Deep layer
36,730
Total organic
1,000
Lithosphere
Sedimentary carbonates
>60,000,000
Kerogens
15,000,000
Terrestrial biosphere (total)
~2,000
Living biomass
600-1,000
Dead biomass
1,200
Aquatic biosphere
1-2
Fossil fuels
4,130
Coal
3,510
Oil
230
Gas
140
Other (mainly peat)
250
Reproduced with permission from Falkowski et al. (2000). © AAAS.
a
1Gtis10
9
metric tons = 10
12
kg.
Oceans store approximately 50 times more CO
2
than the atmosphere. There is a
dynamic exchange by diffusion of about 90 Gt C per year between oceans and the
atmosphere, showing the importance of the oceans in CO
2
capture processes. This
capture by dissolution leads to ionic bicarbonate formation and increased acidity of
the water. Buffering of changes in atmospheric CO
2
concentrations is limited and
is very much related to the release of cations from comparatively slow rock weath-
ering. Relevant reactions are:
HCO
3
−
+H
+
CO
2
+H
2
O
$
ð
RX
1
1
Þ
:
:
HCO
3
−
+H
2
O
CO
3
2−
+H
+
$
ð
RX
1
2
Þ
:
:
CaSiO
3
+CO
2
!
CaCO
3
+ SiO
2
ð
RX
1
3
Þ
:
:
In the deep ocean (below ~300 m), the concentration of carbonates is higher than at
the surface level, which is a consequence of two processes, called the oceanic
“
sol-
ubility pump
mechanisms. The first is related to the better
solubility of CO
2
in cold saline waters, which are in particular present at the Earth
”
and
“
biological pump
”
s
higher latitudes. These take up CO
2
, sink to lower levels, and redistribute the solution
laterally. However, a CO
2
-induced global temperature rise leads to a more stable
height profile of water (a phenomenon called stratification), by which transport of
'
Search WWH ::
Custom Search