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reduction of 2010 anthropogenic emissions to account
for anticipated future growth in emissions.
Table 3.7.
Storage reservoirs of carbon in Earth's
atmosphere, oceans, sediments, and land in 2011
Gigatonnes
Example 3.7
For an emission rate of 8,400 Tg-C yr
−1
from fossil
fuels and 1,800 Tg-C yr
−1
from permanent defor-
estation, calculate the equilibrium mixing ratio of
CO
2
(g) in the atmosphere assuming an overall
lifetime of 40 years.
Location and form of carbon
of carbon
Atmosphere
Gas and particulate carbon
859
Surface oceans
Live organic carbon
Dead organic carbon
Bicarbonate ion
5
30
500
Solution
The total anthropogenic emission rate of 10,200
Tg-C yr
−1
is first converted to ppmv-CO
2
(g)/yr
with 2,184.82 Tg-C/ppmv-CO
2
(g), giving
E
Deep oceans
Dead organic carbon
Bicarbonate ion
3,000
40,000
4.67
ppmv-CO
2
(g) yr
−1
. Substituting this emission rate
into
=
Ocean sediments
Dead organic carbon
a
(
∞
)
=
E
gives 187 ppmv. Adding this
10,000,000
to
275 ppmv gives the steady-state total
mixing ratio,
b
=
Land/ocean sediments
Carbonate rock
(
∞
)
=
462 ppmv CO
2
(g).
60,000,000
Land
Live organic carbon
Dead organic carbon
800
2,000
Example 3.8
In 2030, the projected fossil fuel plus perma-
nent deforestation emission rate for the world
is expected to be 12,800 Tg-C yr
−1
.Whatper-
cent reduction in 2030 anthropogenic emissions
is needed to stabilize the atmospheric mixing
ratio of CO
2
(g) to 360 ppmv? What percent of
2010 anthropogenic emissions does this reduc-
tion represent?
nearest carbon-containing rival, CH
4
(g). The atmo-
spheric mass of carbon pales in comparison with the
mass of carbon in other reservoirs, particularly the deep
oceans, ocean sediments, and carbonate rocks. Table
3.7 shows the relative abundance of carbon in each
reservoir.
Exchanges of carbon among the reservoirs include
exchanges between the surface ocean (0-60 m below
sea level) and deep ocean (below the surface ocean) by
up- and down-welling of water. Exchanges also occur
between the deep ocean and sediments by gravitational
sinking and burial of dead organic matter and shell
material, between the sediments and atmosphere by vol-
canism, between the land and atmosphere by oxygen-
producing photosynthesis and bacterial metabolism,
and between the surface ocean and atmosphere by evap-
oration and dissolution.
Solution
The emission rate needed to stabilize CO
2
(g) at
atotal mixing ratio of
=
360 ppmv is
E
=
a
(
2.125
ppmv yr
−1
.Multiplying this by 2,184.82 Tg-
C/ppmv-CO
2
(g) gives 4,642.74 Tg-C yr
−1
. The
2030 emission rate reduction needed is, there-
fore, 8,160 Tg-C yr
−1
,ora63.7percent reduc-
tion. This reduction represents 80 percent of the
2010 emission rate of 10,200 Tg-C yr
−1
.
∞
)
/
=
(360
−
275 ppmv)/40 years
=
3.6.2.4. Carbon Reservoirs
At 393 ppmv CO
2
(g) in 2011, the atmosphere con-
tained about 859 gigatonnes (GT) of carbon (1 ppmv-
CO
2
(g)
3.6.2.5. Health Effects
Carbon dioxide mixing ratios must be higher than
15,000 ppmv to affect human respiration. Mixing ratios
higher than 30,000 ppmv cause headaches, dizziness,
or nausea (Schwarzberg, 1993). In indoor air, carbon
dioxide mixing ratios may build up enough to cause
discomfort, but levels above 15,000 ppmv are rare. Out-
door mixing ratios of carbon dioxide are almost always
too low to cause noticeable direct health impacts. One
10
9
10
15
=
2,184.82 Tg-C; 1 GT
=
tonnes
=
g
1,000 Tg). Almost all carbon in the air is in its most
oxidized form, CO
2
(g), but some is in its most reduced
form, methane [CH
4
(g)], and in many inorganic and
organic gas and particle components. The mass of car-
bon in airborne CO
2
(g) is more than 200 times that of its
=
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