TY  - GEN
A1  - Polag, Daniela
Y1  - 2009///
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/9465/
KW  - stable isotopes 
KW  -  fractionation 
KW  -  kinetics 
KW  -  laboratory experiments
N2  - In recent years, stalagmites have become an important archive for paleoclimate. Several studies about stable isotope records in stalagmites show a simultaneous enrichment of d18O and d13C along individual growth layers, which is associated with kinetic isotope fractionation. However, to deduce paleoclimatic information from calcite which is precipitated under these non-equilibrium-conditions,it is important to improve the understanding of kinetic isotope fractionation in dependence of local conditions like temperature and drip rate. Within this research work, laboratory experiments with synthetic carbonates were carried out under controlled conditions. The d18O and d13C evolution of the precipitated calcite were studied for different experiment parameters such as the initial composition of the solution, temperature and drip rate. In addition, in situ experiments were carried out in two cave systems in Sauerland (Bunkerhöhle and B7-Höhle). The modern calcite collected at three drip sites was compared with the calcite obtained from the laboratory experiments. All experiments show a distinct isotopic enrichment along the precipitated calcite. Lower drip rates, higher temperatures and higher initial supersaturation with respect to calcite result in a greater total isotopic enrichment and in a lower slope of the linear correlation d18O(d13C). The latter indicates a larger oxygen isotope buffering from the water reservoir. From a comparison with theoretical models it can be concluded that the conversion reactions between the bicarbonate and the carbon dioxid and the exchange reactions between the oxygen isotopes in the bicarbonate and the water reservoir occur faster than predicted from present publications, particularly in case of higher temperatures (23°C). Thus, for higher temperatures other effects might play a role not yet considered in theoretical models.
ID  - heidok9465
AV  - public
TI  - Kinetic fractionation of stable isotopes in speleothems : laboratory and in situ experiments
ER  -