231Pa/230Th fractionation by ocean transport, biogenic particle flux and particle type
231Pa/230Th fractionation by ocean transport, biogenic particle flux and particle type
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DOI：
10.1016/j.epsl.2005.05.031
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发表时间：
2005-08
影响因子：
5.3
通讯作者：
M. Siddall;G. Henderson;N. Edwards;M. Frank;S. Müller;T. Stocker;F. Joos
中科院分区：
文献类型：
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作者：
M. Siddall;G. Henderson;N. Edwards;M. Frank;S. Müller;T. Stocker;F. Joos
231Pa和230th通过可逆清除过程从水柱中去除，该过程迅速将230th去除到沉积物中。231Pa被颗粒清除的效率低于2330s，因此在到达海洋沉积物之前更有效地通过平流和扩散输送。本研究将观测所得的粒子场（粉尘、蛋白石、CaCO3、POC）与Bern3D中等复杂性海洋模型和同位素平衡清除模型相结合。颗粒与溶解同位素活度的平衡分配系数随颗粒类型而变化。该模型可以解释全球231pa和2330s分布的许多特征。这样一个简单的模式成功地代表了231pa /230Th活度比的全球格局，支持了该代理在古海洋学研究中的使用。我们使用该模型来解决关于哪种颗粒类型在海洋中231pa /230Th分选中占主导地位的争议。岩石（尘）通量对231pa /230Th分选不重要，231pa /230Th的海洋分选主要由caco3和蛋白石通量的分布决定。我们还确认蛋白石是230的弱清除剂。
231Pa and230Th are removed from the water column by a process of reversible scavenging which quickly removes230Th to the sediment.231Pa is less efficiently scavenged onto particles than230Th and is therefore more effectively transported via advection and diffusion before it reaches the ocean sediment. This study combines particle fields (dust, opal, CaCO3, POC) derived from observations with the Bern3D intermediate complexity ocean model and an equilibrium-scavenging model for isotopes. The equilibrium partition coefficient for particulate versus dissolved isotope activity is varied with particle type. The model can explain many of the features of the global231Pa and230Th distribution. The success of such a simple model at representing the global pattern of231Pa/230Th activity ratio supports the use of this proxy in paleoceanographic studies. We use the model to address the controversy concerning which particle types are dominant in fractionating231Pa/230Th in the ocean. The lithogenic (dust) flux is found to be unimportant for231Pa/230Th fractionation— the ocean fractionation of231Pa/230Th is dominated by the distribution of the CaCO3and opal flux. We also confirm that opal is a weak scavenger of230Th.