贵州七星洞系统中水文地球化学特征对滴水δ^(13)C_(DIC)的影响及其意义  

Effects of hydrogeochemistry on δ~13C_(DIC) values of drip water in Qixing Cave,Guizhou,China and their implications

作　　者：王世杰[1] 罗维均[1] 刘秀明[1] 谢兴能[1] 周运超[1] 黎廷宇[1] 刘启明[1] 

机构地区：[1]中国科学院地球化学研究所环境地球化学国家重点实验室,贵州贵阳550002

出　　处：《地学前缘》2009年第6期66-76,共11页Earth Science Frontiers

基　　金：中国科学院知识创新工程方向性项目(kzcx2-yw-306);创新团队国际合作伙伴计划;国家重点基础研究发展计划"973"项目(2006CB403200);国家自然科学基金项目(90202003);贵州省科学技术基金(黔科合J字[2008]2219)

摘　　要：2003年4月至2004年5月,笔者对贵州七星洞(QXD)进行了较为详细的监测,逐月采集了土壤水和洞穴滴水等样品,分别测定了样品的稳定碳同位素组成和水文地球化学参数。结果显示,9个滴水点同期的溶解无机碳同位素值(δ13CDIC)之间存在着大的差异,最大达6.9‰;δ13CDIC值偏重的Ⅰ组滴水,其Ca、Sr、HCO3、电导率(EC)和方解石饱和指数(SIC)等水文地球化学指标偏小,而Mg/Ca比值偏大,Ⅱ组则相反;不同滴水点的δ13CDIC值分别与相应滴水的Ca、Sr、HCO3、EC、Mg/Ca和SIC等水文地球化学指标之间存在较好的相关关系。进一步分析表明,与土壤水δ13CDIC平均值-9.9‰相比,Ⅰ组1#、2#、6#、7#和8#滴水点δ13CDIC值偏重4.5‰～5.7‰,主要是由大量的基岩溶解以及前期方解石沉积(prior calcite precipitation,PCP)共同作用的结果;Ⅱ组3#、4#、5#和9#滴水点δ13CDIC值偏重0.6‰～1.6‰,受基岩溶解和PCP过程影响较小,尤其是9#滴水点受影响最小。因此,若不考虑基岩溶解和PCP过程影响作用,将会极大地影响洞穴化学沉积物碳同位素记录的准确解释。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 δ^13CDIC 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 δ^13CDIC 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 δ^13CDIC 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 δ^13CDIC 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 δ^13CDIC of cave drip waters are controlled to some extend by hydrogeochemistry.In comparison with average δ^13CDIC value-9.9‰ of soil waters,δ^13CDIC 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 δ^13C recorded in speleothems can not be guaranteed if not considering the effects of the above mentioned hydrogeochemical processes.

关 键 词：洞穴滴水 水文地球化学特征 稳定碳同位素 相关性 贵州七星洞 

分 类 号：P59[天文地球—地球化学] P641.3[天文地球—地质学]