南海砗磲Sr/Ca比值测试：XRF和ICP-OES方法对比研究

对采自中国南海的5个砗磲(1个现代砗磲、4个化石砗磲)进行了两种高分辨率Sr/Ca比值分析。电感耦合等离子体发射光谱法(ICP-OES)得到的Sr/Ca比值呈现出年周期变化，且与海表面温度呈现负相关关系，这表明Sr/Ca可作为良好的SST替代性指标。ICP-OES是测试砗磲壳体Sr/Ca常用的方法，但大量的样品需要钻样及预处理，相当耗时。而同步辐射X射线荧光分析(SR-XRF)可以克服这些缺点，它只需要前期的样品制备，并允许固态样品原位无损快速分析，具有高空间分辨率(微米级)、高灵敏度和多元素分析的特点。在本研究中，我们用SR-XRF方法测试砗磲样品化学元素的可行性。据查阅，目前尚未有类似的相关研究文献。本文实验结果显示SR-XRF 数据能够揭示元素含量及其比值变化。且SR-XRF测得的砗磲Sr/Ca比值与ICP-OES分析方法测得的Sr/Ca通过相关统计分析发现其显著性水平p值(5个砗磲样品的p值均<0.05)非常显著，表明高分辨率SR-XRF测得的砗磲Sr/Ca比值在一定程度上代替ICP-OES分析方法的可能性非常大。SR-XRF方法在砗磲重建古气候领域有很大的应用前景。

Measurement of Sr/Ca Ratio in Tridacna spp. Shells from South China Sea: A Comparison of SR-XRF and ICP-OES Analysis Methods

Two different analysis methods were applied and compared for determining high-resolution Sr/Ca ratio profiles of one modern (live-caught) and four fossil (dead-collected) Tridacna spp. samples from South China Sea. The Sr/Ca profile of Tridacna gigas in the South China Sea determined by Inductively coupled plasma optical emission spectrometry (ICP-OES) had well defined annual cycles and was significantly, negatively correlated with sea surface temperature, implying that they can be used as good proxies of historical Sea Surface Temperature (SST). ICP-OES is an commonly used method for measuring Sr/Ca ratios in Tridacna spp. shells, but it needs ex-situ, time-consuming chemical pretreatments using variable acids and considerable amounts of sample. While the synchrotron radiation X-ray fluorescence (SR-XRF) technique does not have these shortcomings, it requires little sample preparation and allows rapid in situ analysis of solid-state samples at high spatial resolution (submicron scales), and it is characterized by non-destructive, high sensitivity, and multi-elemental distribution. In this study, we tested the feasibility of determining chemical elements in shell samples of Tridacna spp. by using SR-XRF. To the best of our knowledge, no similar studies have been reported in the literature.Our study showed that the data of SR-XRF can reflect the elements contents and their ratios change. SR-XRF derived Sr/Ca ratio profiles are significantly correlated with those from ICP-OES (P-values for five Tridacna spp. samples are all <0.05); therefore, SR-XRF can be a promising alternative to ICP-OES. And it has a broad application potential in palaeoclimate reconstructions by using Tridacna spp..