Abstract:

 Monitoring and sampling of soil waters and cave drip waters during the periods from April 2003 to May 2004 were performed monthly at Qixing Cave, Duyun, Guizhou, southwest China, in order to understand the effects of hydrogeochemisty on δ13CDIC of cave drip waters and their implications for interpreting the potential paleoenvironmental signal preserved in speleothems. The results show that there exists remarkable difference (≤69‰) among δ13CDIC of cave drip waters at 9 sampling sites synchronously. Drip waters are obviously classified into two groups. Compared to Group Ⅱ (3#, 4#, 5# and 9#), Group Ⅰ (1#, 2#, 6#, 7# and 8#) is characterized by heavier δ13CDIC values, smaller Ca, Sr and HCO3 concentrations as well as electrical conductivity (EC) and saturation index for calcite (SIC), and larger Mg/Ca ratio. Good correlations between δ13CDIC of drip water and its corresponding contents of Ca, Sr and HCO3, EC, Mg/Ca, and SIC, respectively, have been found in drip waters. These characteristics imply that δ13CDIC of cave drip waters are controlled to some extend by hydrogeochemistry. In comparison with average δ13CDIC value -9.9‰ of soil waters, δ13CDIC values of drip waters in Group Ⅰ  are heavier up to 45‰57‰, which is caused by the contribution from amounts of bedrock dissolution and prior calcite precipitation (PCP); by contrast, those in Group Ⅱ are slightly heavier (06‰16‰), which is affected less by bedrock dissolution and PCP, especially for 9# drip water. Therefore, the accurate interpretation of δ13C recorded in speleothems can not be guaranteed if not considering the effects of the above mentioned hydrogeochemical processes.

Key words: Key words: cave drip water; hydrogeochemistry; stable carbon isotope; correlation; Qixing Cave, Guizhou