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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Calibration of Na partitioning in the calcitic foraminifer Operculina ammonoides under variable Ca concentration: Toward reconstructing past seawater composition
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Calibration of Na partitioning in the calcitic foraminifer Operculina ammonoides under variable Ca concentration: Toward reconstructing past seawater composition

机译：可变CA浓度下磷酸盐传染率氨基铵氨基铵中Na分配的校准：朝向海水组合物重建

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Reconstructions of past changes in the seawater calcium concentration (Ca-sw) are critical for understanding the long-term changes in ocean chemistry, the carbon cycle and for accurate application of elemental proxies (EI/Ca-CaCO3) in foraminifera (e.g., Mg/Ca as proxy of temperature). Here we show that Na/Ca ratios in foraminiferal shells could be used for reconstructing Ca-sw and Mg/Ca in the past oceans. Ca has a short residence time in the ocean (similar to 1 My), whereas Na in seawater has a residence time of similar to 100 My. Hence it may be reasonably assumed that Na-sw is invariant over the Cenozoic, enabling variations in oceanic Ca to be deduced from foraminiferal Na/Ca (Na/Ca-shell) if Na incorporation into foraminiferal shells depends on Na/Ca in seawater. Furthermore, the paleo-concentrations of other major and minor elements may then be calculated relative to the Ca in the shells, provided that other environmental or biological factors do not present a further complication. To evaluate this hypothesis, we cultured the benthic foraminifer Operculina ammonoides, an extant relative of the Eocene Nummulites, under varying Ca-sw and temperature. The foraminifera grew well under the experimental conditions and increased their weight by 40-90%. The newly grown calcite (identified using a Ba-135 labeling in the experimental seawater) was analyzed by Laser-Ablation ICP-MS for Li, Na, Mg and Sr to Ca ratios. The relationship between Na/Ca and Mg/Ca in the shell and their ratio in the solution are best described as a power function, where the instantaneous distribution coefficient is the derivative of the power fit to the El/Ca-shell versus El/Ca-sw. In contrast, D-sr and D-Li are invariant with El/Ca-sw. The influence of temperature on Li, Na and Sr incorporation was smaller than the uncertainty of our measurements. We conclude that Na/Ca in foraminiferal shells can be used to calculate paleo-calcium concentrations in the oceans and also other elements that may
机译：海水钙浓度（CA-SW）的过去变化的重建对于了解海洋化学，碳循环和准确应用的青少年（例如，Mg）的长期变化是至关重要的（例如，mg）的长期变化（EI / Ca-CaCO 3） / ca作为温度代理）。在这里，我们表明，火山虫壳中的Na / Ca比可以用于在过去的海洋中重建Ca-SW和Mg / Ca。 CA在海洋中有一个短暂的住宿时间（类似于1我），而海水中的NA具有类似于100我的住宿时间。因此，如果Na掺入火山虫壳中，则可以合理地假设Na-SW在新生代中的不变性，从新生代掺入从多孔酰胺Na / Ca（Na / Ca-shell）中所推断的海洋Ca的变化取决于海水中的Na / Ca。此外，可以相对于壳中的Ca来计算其他主要和次要元素的古浓度，只要其他环境或生物因素不存在进一步的并发症。为了评估该假设，我们培养了底栖传染症杂志，在不同的Ca-SW和温度下培养了eoceneuulites的远端相对。 Foraminifera在实验条件下浓得很好，重量增加40-90％。通过激光烧蚀ICP-MS进行Li，Na，Mg和Sr，对Ca比的激光消融ICP-MS进行分析新种植的方解石（使用实验海水中的标记）。壳体中Na / Ca和Mg / Ca之间的关系及其在溶液中的比率最好被描述为功率函数，其中瞬时分布系数是拟合EL / CA-Shell的功率的导数与EL / CA -sw。相比之下，D-SR和D-Li具有EL / CA-SW的不变。温度对Li，Na和Sr掺入的影响小于我们测量的不确定性。我们得出结论，火山虫壳中的Na / Ca可用于计算海洋中的古钙浓度以及可能的其他元素

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