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
'
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