Behavior of Nd isotopes at the Ocean-Sediment Boundary: Addressing the "Nd Paradox"

新大洋同位素比值（143 Nd/144 Nd）越来越多地被用作过去海洋环流模式的示踪剂。然而，我们对海洋Nd动力学的理解，以及Nd作为海洋示踪剂的可靠性，目前由于Nd的同位素组成（在海洋盆地之间是独特的）和元素Nd的分布（似乎是由水柱循环驱动）之间的明显脱节而变得复杂。解决这一“Nd悖论”对于完善过去海洋行为的示踪研究非常重要。以往的研究表明，同位素和元素Nd的去耦可能发生在海洋沉积物和底层沃茨之间的界面附近。这项研究，由研究人员在俄勒冈州州立大学，调查之间的交换反应溶解和颗粒Nd发生在这个接口和周围，重点是成岩沉积过程的影响Nd同位素比值。将沿俄勒冈州大陆边缘沿着采集孔隙水、沉积物和水柱样本，并分析Nd同位素和其他相关示踪剂（包括稀土元素、碳和氮）。由此产生的数据集不仅有助于解决Nd悖论，而且还将应用于未来的概念和化学建模工作，这反过来又将为古海洋学和古气候模型的开发提供信息。该项目将纳入COSEE（海洋科学教育卓越中心）太平洋伙伴关系海洋扫盲工作。PRIME（促进海洋环境研究调查）实习生，以及两个俄勒冈州立大学的学生（博士和本科），将参与这项研究。该项目包括与布里斯托大学的一名地球化学家进行国际合作，这将加强俄勒冈州州立大学的分析能力。资金还将帮助支持俄勒冈州州立大学的一名早期职业研究人员。

Neodymium isotope ratios (143Nd/144Nd) are increasingly used as tracers of past ocean circulation patterns. However, our understanding of marine Nd dynamics, and thus the reliability of Nd as an oceanic tracer, is currently complicated by an apparent disconnect between the isotopic compositions of Nd (which are distinctive between ocean basins) and the distribution of elemental Nd (which appears to be driven by water column cycling). It is important to resolve this "Nd paradox" in order to refine tracer studies of past ocean behavior. Prior research suggests that the decoupling of isotopic and elemental Nd may occur near the interface between marine sediments and bottom waters. This study, conducted by researchers at Oregon State University, investigates exchange reactions between dissolved and particulate Nd occurring at and around this interface, with a focus on the influence of diagenetic sedimentary processes on Nd isotope ratios. Porewater, sediment, and water column samples will be collected along the Oregon continental margin and analyzed for Nd isotopes and other relevant tracers (including rare earth elements, carbon, and nitrogen). The resulting dataset will not only help to resolve the Nd paradox, but will also be applied to future conceptual and chemical modeling efforts, which in turn will inform the development of paleoceanographic and paleoclimatic models.This project will be incorporated into the COSEE (Center for Ocean Science Education Excellence) Pacific Partnerships ocean literacy effort. A PRIME (Promoting Research Investigations in the Marine Environment) intern, as well as two OSU students (PhD and undergraduate), will be involved in this research. The project includes international collaboration with a geochemist from the University of Bristol, which will strengthen Oregon State University's analytical capabilities. Funding will also help support an early-career researcher at Oregon State University.