Geoscience Reference
In-Depth Information
Dissolved CO in mg
2
l
-1
2500
2000
1500
1000
500
0°
20°
40°
60°
80°
100°
120°
Temperature in °C
Fig. 7.8
Solubility of CO
2
in water under one atmosphere of pure gas (BRGM 1997).
Table 7.2
Variation in solubility of CaCO
3
with CO
2
content.
Solubility of CaCO
3
at 10 °C, mg l
-1
P CO
2
, %
6 mg l
-1
0
60 mg l
-1
0.0381 (value of the atmosphere)
180 mg l
-1
1 (possible value in soils)
300 mg l
-1
4
Biological activity is thus liable to load rainwater with CO
2
and to
augment three-fold or even more the aggressiveness of the water.
The CO
2
content is also linked to a very important factor, namely, the
nature (open or closed) of the reaction environment. In other words, as
the available CO
2
in the water is consumed by dissolution, is it replaced
by new CO
2
provided by the atmosphere?
Table 7.3 (Chamayou and Legros 1989) gives the values obtained in
the two cases considered.
Table 7.3
Dissolution of CaCO
3
in systems open or closed to the air.
Parameter
System open to
System closed to
the air
the air
Ca
2+
in mg l
-1
16
6.0
Corresponding CaCO
3
in mg l
-1
49
12.5
pH
8.3
9.95
Final CO
2
content in mg l
-1
0.44
0
