Fractionation Mechanisms of Carbon Isotopes
25
Table 6. Experimentally determined carbon isotope fractionations between dissolved bicarbonate and gaseous C02 (the values are calculated for 20° C, using a
temperature dependence of -0.109%01" C)
Author
VOGEL (1961)
ABELSON and HOERING (1961)
DEUSER and DEGENS (1967)
WENDT (1968)
EMRICH et al. (1970)
Fractionation in %0
(20° C)
7.9
7.8
7.6
8.2
8.4
3) Other important processes producing isotope fractionations in
the carbon cycle on a wide scale are:
a) A kinetic effect arises during the thermal cracking of hydrocarbons. FRANK and SACKETT (1969) have found a 13C depletion in methane
generated during the thermal cracking of neopentane. This suggests that
500 300
Temperature,OC
60Pi,00:
200 15012010080 6050403020 10
70
60
50
~40
.5
M
Q
30
o I 2 3 4 5 6 7 8 9 10 II 12 13
1I0 3 /T)2, °K- 2
Fig. 8. Calculated carbon isotope fractionation factors for exchange among graphite, calcite, carbon dioxide, and methane. (After BOTTINGA, 1969a)
25
Table 6. Experimentally determined carbon isotope fractionations between dissolved bicarbonate and gaseous C02 (the values are calculated for 20° C, using a
temperature dependence of -0.109%01" C)
Author
VOGEL (1961)
ABELSON and HOERING (1961)
DEUSER and DEGENS (1967)
WENDT (1968)
EMRICH et al. (1970)
Fractionation in %0
(20° C)
7.9
7.8
7.6
8.2
8.4
3) Other important processes producing isotope fractionations in
the carbon cycle on a wide scale are:
a) A kinetic effect arises during the thermal cracking of hydrocarbons. FRANK and SACKETT (1969) have found a 13C depletion in methane
generated during the thermal cracking of neopentane. This suggests that
500 300
Temperature,OC
60Pi,00:
200 15012010080 6050403020 10
70
60
50
~40
.5
M
Q
30
o I 2 3 4 5 6 7 8 9 10 II 12 13
1I0 3 /T)2, °K- 2
Fig. 8. Calculated carbon isotope fractionation factors for exchange among graphite, calcite, carbon dioxide, and methane. (After BOTTINGA, 1969a)