Benchtop μXRF as a tool for speleothem trace elemental analysis: Validation, limitations and application on an Eemian to early Weichselian (125–97 ka) stalagmite from Belgium
Benchtop μXRF as a tool for speleothem trace elemental analysis: Validation, limitations and application on an Eemian to early Weichselian (125–97 ka) stalagmite from Belgium
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台式μXRF作为洞穴微量元素分析的工具：对来自比利时的埃米安至早期Weichselian（125-97ka）石笋的验证、限制和应用
DOI：
10.1016/j.palaeo.2019.109460
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
Philippe Claeys
中科院分区：
文献类型：
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作者：
Vansteenberge Stef;De Winter Niels J;Sinnesael Matthias;Zhao Xueqin;Sophie Verheyden;Philippe Claeys
沿洞穴植物生长轴的微量元素（例如 Mg、Sr、Ba、Fe、Zn 等）浓度变化构成了重要的古气候指标。过去已经探索过使用实验室微 X 射线荧光光谱法作为传统质谱技术的快速且廉价的替代品来进行洞穴微量元素分析，并取得了令人满意的结果。然而，在洞穴动物界内，需要深入研究这种分析技术的全部潜力。与其他类型的古气候档案相比，由于洞穴体基质结晶度高且感兴趣元素丰度低，对洞穴体进行台式 (μ)XRF 分析在分析上更具挑战性。在这项研究中，研究了几种在矿物学（方解石与文石）和成分方面存在差异的洞穴沉积物样品。测试了各种仪器参数，并为未来将 (μ)XRF 分析应用于洞穴的研究提出了建议。基于多个标准校准和误差评估进行量化。通过质谱技术验证，证实台式 μXRF 装置能够生成洞穴微量元素记录。对 Sr、Mg 和 Fe 获得了成功的结果，同时对高浓度样品中的 Zn 和 Ba 进行了定量。然而，由于样品结晶度引起的衍射的存在，在解释结果时必须小心。提供可靠结果的元素是特定于样品的，并且取决于基质的类型和元素丰度。这些发现适用于比利时 Han-sur-Lesse 洞穴的埃米亚期至早期威克塞尔期石笋。构建了 Mg 和 Sr 的时间序列，与先前获得的稳定同位素（δ13C 和 δ18O）比率、生长速率和石笋形态一起创建了多代理数据集。看来镁和锶主要不是受先前方解石降水的控制，而是受洞穴上方植被活动变化的控制。
Variations of trace element (e.g. Mg, Sr, Ba, Fe, Zn etc.) concentrations along a speleothem's growth axis constitute important paleoclimate proxies. The use of laboratory micro X-ray fluorescence spectrometry as a fast and cheap alternative for conventional mass spectrometry techniques for trace element analysis on speleothems has been explored in the past and yielded satisfactory results. However, within the speleothem community there is need for an in-depth investigation of the full potential of this analytical technique. Compared to other types of paleoclimate archives, benchtop (μ)XRF analysis on speleothems is analytically more challenging because of the high-crystalline speleothem matrix and the low abundance of the elements of interest. In this study, several speleothem samples with differences in mineralogy (calcite versus aragonite) and composition are investigated. Various instrumental parameters are tested and recommendations are made for future studies applying (μ)XRF analysis to speleothems. Quantification based on a multiple standard calibration and an assessment of the error is carried out. Through validation with mass spectrometry techniques, it is confirmed that benchtop μXRF devises are able to generate speleothem trace element records. Successful results were obtained for Sr, Mg and Fe, while Zn and Ba were quantified in samples characterized by high concentrations. Nevertheless, caution has to be taken when interpreting the results, due to the presence of diffraction caused by the crystallinity of the samples. The elements which provide reliable results are sample specific and depend on the type of matrix and elemental abundance. These findings are applied on an Eemian to early Weichselian stalagmite from the Han-sur-Lesse Cave, Belgium. Time series were constructed for Mg and Sr, creating a multiproxy dataset together with previously obtained stable isotope (δ13C and δ18O) ratios, growth-rate and stalagmite morphology. It appears that Mg and Sr are not primarily controlled by prior calcite precipitation, but rather by changes in vegetation activity above the cave.