An interlaboratory study of TEX 86 and BIT analysis of sediments, extracts, and standard mixtures: TEX 86 and BIT Index Round Robin
An interlaboratory study of TEX 86 and BIT analysis of sediments, extracts, and standard mixtures: TEX 86 and BIT Index Round Robin
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沉积物、提取物和标准混合物的 TEX 86 和 BIT 分析的实验室间研究：TEX 86 和 BIT 索引循环
DOI：
10.1002/2013gc004904
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Brocks, Jochen J.
中科院分区：
文献类型：
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作者：
Schouten, Stefan;Hopmans, Ellen C.;Rosell-Melé, Antoni;Pearson, Ann;Adam, Pierre;Bauersachs, Thorsten;Bard, Edouard;Bernasconi, Stefano M.;Bianchi, Thomas S.;Brocks, Jochen J.
基于甘油二烷基甘油四醚（GDGT）分布的两个常用替代物是用于重建海表面温度的TEX 86（86个碳原子的四醚指数）古温度计和用于重建土壤有机质输入海洋的BIT（支链类异戊二烯四醚）指数。对两种沉积物提取物进行的初步循环研究（有15个实验室参与）显示出相对一致的TEX 86值（转换为温度时的再现性为±3-4°C），但BIT测量值的范围很大（再现性为±0.41，范围为0-1）。在这里，我们报告了与35个实验室进行的第二轮研究的结果，其中分析了三种沉积物，一种沉积物提取物和两种纯的分离GDGT混合物。TEX 86和BIT指数的结果显示与之前的循环研究相比有所改善。当转换为温度时，TEX 86值的再现性（表明实验室间差异）范围为1.3至3.0°C。这些结果与古海洋学中使用的其他温度代用指标的结果相似。从三个沉积物中的一个得到的结果的比较表明，TEX 86和BIT指数没有显着影响实验室间的差异，沉积物提取技术。沉积物和提取物的BIT值处于指数的极端值，接近0或1，并且显示出良好的再现性（范围从0.013到0.042）。然而，对于具有已知的crenarchaeol和支链GDGT的摩尔比的两种GDGT混合物，测量的BIT值具有中间BIT值，并且显示出差的再现性和对“真实”（即，基于摩尔）BIT指数。后者可能是由于，除其他因素外，与crenarchaeol相比，支链GDGT的质谱响应更高，这也在质谱仪之间变化。对这种不同质谱响应的校正表明，实验室之间BIT指数测量的重现性有了相当大的改善，以及基于摩尔的BIT值的估计也有了实质性的改善。这表明应使用标准混合物以获得一致的、基于摩尔的BIT值。
Two commonly used proxies based on the distribution of glycerol dialkyl glycerol tetraethers (GDGTs) are the TEX86(TetraEther indeX of 86 carbon atoms) paleothermometer for sea surface temperature reconstructions and the BIT (Branched Isoprenoid Tetraether) index for reconstructing soil organic matter input to the ocean. An initial round‐robin study of two sediment extracts, in which 15 laboratories participated, showed relatively consistent TEX86values (reproducibility ±3–4°C when translated to temperature) but a large spread in BIT measurements (reproducibility ±0.41 on a scale of 0–1). Here we report results of a second round‐robin study with 35 laboratories in which three sediments, one sediment extract, and two mixtures of pure, isolated GDGTs were analyzed. The results for TEX86and BIT index showed improvement compared to the previous round‐robin study. The reproducibility, indicating interlaboratory variation, of TEX86values ranged from 1.3 to 3.0°C when translated to temperature. These results are similar to those of other temperature proxies used in paleoceanography. Comparison of the results obtained from one of the three sediments showed that TEX86and BIT indices are not significantly affected by interlaboratory differences in sediment extraction techniques. BIT values of the sediments and extracts were at the extremes of the index with values close to 0 or 1, and showed good reproducibility (ranging from 0.013 to 0.042). However, the measured BIT values for the two GDGT mixtures, with known molar ratios of crenarchaeol and branched GDGTs, had intermediate BIT values and showed poor reproducibility and a large overestimation of the “true” (i.e., molar‐based) BIT index. The latter is likely due to, among other factors, the higher mass spectrometric response of branched GDGTs compared to crenarchaeol, which also varies among mass spectrometers. Correction for this different mass spectrometric response showed a considerable improvement in the reproducibility of BIT index measurements among laboratories, as well as a substantially improved estimation of molar‐based BIT values. This suggests that standard mixtures should be used in order to obtain consistent, and molar‐based, BIT values.