介形虫碳氧同位素测定样品处理方法对比研究

Comparative Study on Sample Preparation in Carbon and Oxygen Isotope Analyses of Lake Ostracode Shells

介形虫化石壳体被认为是反映古湖泊沉积环境的理想对象。在过去的30年,介形虫壳体的δ13C和δ18O测定已经被广泛应用到湖泊沉积古气候及古环境的重建。由于湖泊生物碳酸盐样品不同的前处理方法可能会影响到稳定同位素测试结果的重现性和辨析率以及实验室之间数据的可比性,采用有效的方法对介形虫壳体进行预处理是保证介壳稳定同位素测试的一个关键环节。在总结目前常用的湖泊生物碳酸盐稳定同位素测试样品处理方法的基础上,通过对青海湖现代和古代沉积物中介形虫的测定,讨论各种处理方法对介形虫壳体稳定同位素测试结果(δ13C和δ18O)的影响。实验表明:不同处理方法对所测介壳样品的δ13C值和δ18O值不会产生大的影响,在介壳样品的稳定同位素测试之前不需要对介壳样品进行处理。

Stable isotopic composition of fossil ostracode is used as an ideal proxy for paleo-lake sedimentary environments. Over the last three decades,measurements of the δ^13C and δ^18O values of ostraoode shells have been extensively used in lake palaeoenvironmental reconstruction. Many methods for sample preparation have been applied in stable isotope measurements of ostracode shells from lake sediments. However, for stable isotope measurements of biocarbonate samples, different methods will probably affect the resolution, reproducibility and inter-laboratory comparison of the measurement results. In this paper, previous methods of sample preparation for biocarbonate isotopic measurements are compared, with their effects on δ^13C and δ^18O analyses evaluated.The results suggest that different methods will not result in remarkable differences in δ^13C and δ^18O measurements of lake ostracode shells.Therefore, sample cleaning procedure is considered unnecessary for such analyses.