河蚬壳体与水体的无机碳同位素关系

Measurement of δ^(13)C in Bivalve Shells: Implications for Dissolved Inorganic Carbon Reconstructions

河流溶解无机碳对于评价区域水环境的碳循环具有重要意义,若能获得古水体DIC的地球化学特征,则可以为重建过去环境变化提供大量基础数据,因此寻找δ13CDIC替代指标十分迫切。对花溪河淡水双壳类河蚬进行了室内养殖研究,结果表明:河蚬壳体碳同位素与生长期间水体δ13CDIC存在显著正相关关系,δ13CDIC是影响δ13Cshell的重要因素,壳体记录了其形成时期水体的信息,δ13Cshell可以用作δ13CDIC定性的替代指标来区分具有不同δ13CDIC值的水环境。由于新陈代谢作用的影响,利用δ13Cshell重建的δ13CDIC值与真实的δ13CDIC值相比,平均偏负约2.00‰,且这种差异随着河蚬年龄的增大而增大,因此δ13Cshell不能够直接用来定量提取水体δ13CDIC。

Stable isotope of Dissolved Inorganic Carbon is a very useful indicator for evaluation of carbon sources, sinks, and fluxes. Because of the difficulties in measurement of δ13CDIC, it is urgent to find a proxy of δ13CDIC. Stable carbon isotope in bivalve shells is a potential target. In this study, modern bivalve Corbicula is bred for experiment, and the results show that： δ13Cshell is highly correlated with δ13CDIC, and this significant correlation is due to markedly differences of δ13CDIC between the culture environment and the metabolic effects of the shells. δ13Cshell can not directly be used to quantitatively extract the δ13CDIC, but the high correlation between δ13Cshell and δ13CDIC implies that δ13Cshell can be used as a promising qualitative proxy of large scale variations in δ13CDIC. The future work should focus on the contribution of metabolic effects to δ13Cshell.