Applications of Chemical Kinetics in Environmental Systems - Elements of Environmental Engineering: Thermodynamics and Kinetics - page 339

( a )

380

360

-100

340

-200

320

-300

-400

( b )

8

7

-8.1

6 -8.0

-7.9

-7.8

5

-7.7

-7.6

4
1970

1975 1980 1985 1990

Ye a r

1995 2000 2005

FIGURE 6.39 Monthly average CO 2 concentration observed continuously at Mauna Lao,
Hawaii. (Reprinted from Solomon, S., Qin, D., Chen, Z., Marquis, M., Averyt, K.B., Tignor,
M.,and.Miller,H.L.(Eds) IPCC2007:ClimateChange2007:ThePhysicalBasis.Contribution
of working group 1 to the fourth assessment report of the Intergovernmental Panel on Climate
Change, Cambridge, United Kingdom, and NewYork: Cambridge University Press, 996 pp.)

Let us turn our attention toward some of the natural processes that remove
GHG from the atmosphere. We will focus on CO 2 in the following discussion. The
most significant pathway is the dissolution of CO 2 in the ocean water and final
conversion to HCO 3 and CO 2 −

. This fixing of carbon is rapid in the ocean surface

3

( 500 m of the upper mixed layer), and hence can be considered to be an equilib-

rium process. Weathering of rocks and minerals, dissolution of CaCO 3 in oceans,
and increased bacterial activity in some regions also contribute to the transfer of CO 2
from the atmosphere to the oceans.

∼