Foraminifera Iodine to Calcium Ratios: Approach and Cleaning
Foraminifera Iodine to Calcium Ratios: Approach and Cleaning
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有孔虫碘钙比例：方法和清洁
DOI：
10.1029/2021gc009811
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Winkelbauer H
中科院分区：
文献类型：
--
作者：
Winkelbauer H
浮游和底栖有孔虫碘（I）钙（Ca）的摩尔比已被提出作为一个令人兴奋的新的代理，以评估地下和底层水的氧合在过去。与痕量金属相比，有孔虫方解石中碘的分析更具挑战性，因为碘在酸性溶液中易挥发。在这里，我们比较了先前使用叔胺的分析与使用四甲基氢氧化铵（TMAH）和氢氧化铵（NH 4 OH）稳定溶液中碘的替代分析。此外，我们评估了样本大小和清洁对浮游和底栖有孔虫I/Ca的影响。我们用TMAH和NH 4 OH进行的稳定化实验显示出与使用叔胺的实验类似的趋势，对于来自缺氧沃茨的浮游和底栖有孔虫样品，I/Ca比值相对较低，而对于缺氧沃茨，I/Ca比值较高。这表明这两种替代方法都适用于稳定最初溶解在酸中的碘。含有5-10个样本的样本显示I/Ca的广泛分布。含有20个或更多标本的样品显示出更集中的I/Ca值，表明更大的样本量更能代表平均的南极有孔虫群落。清洁对浮游有孔虫和底栖有孔虫I/Ca比率的影响与Mg/Ca非常相似，在粘土去除步骤中产生的影响最大。最大的碘污染是在有机碳含量中等到高的地点记录的。在这些情况下，我们建议将氧化清洁步骤加倍（4次而不是2次重复），以确保去除所有有机材料。
Planktic and benthic foraminiferal iodine (I) to calcium (Ca) molar ratios have been proposed as an exciting new proxy to assess subsurface and bottom water oxygenation in the past. Compared to trace metals, the analysis of iodine in foraminiferal calcite is more challenging, as iodine is volatile in acid solution. Here, we compare previous analyses that use tertiary amine with alternative analyses using tetramethylammonium hydroxide (TMAH) and ammonium hydroxide (NH4OH) to stabilize iodine in solution. In addition, we assess the effect of sample size and cleaning on planktic and benthic foraminiferal I/Ca. Our stabilization experiments with TMAH and NH4OH show similar trends as those using tertiary amine, giving relatively low I/Ca ratios for planktic and benthic foraminifera samples from poorly oxygenated waters, and high ratios for well‐oxygenated waters. This suggests that both alternative methods are suitable to stabilize iodine initially dissolved in acid. Samples that contain 5–10 specimens show a wide spread in I/Ca. Samples containing 20 specimens or more show more centered I/Ca values, indicating that a larger sample size is more representative of the average planktic foraminifera community. The impact of cleaning on planktic and benthic foraminifera I/Ca ratios is very similar to Mg/Ca, with the largest effect occurring during the clay removal step. The largest iodine contaminations were recorded at locations characterized by moderate to high organic carbon contents. In those circumstances, we recommend doubling the oxidative cleaning steps (4 instead of 2 repetitions) to ensure that all organic material is removed.
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DOI：
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发表时间：
2013
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J. Grützner
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DOI：
10.1029/2020gc009254
发表时间：
2020
期刊：
Geosystems
影响因子：
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作者：
Fehrenbacher, Jennifer;Marchitto, Thomas;Spero, Howard J.
通讯作者：
Spero, Howard J.