Distribution of neodymium isotopes and trace elements in the West Pacific: sources, sinks, and water mass signatures

稀土同位素和稀土元素（REE）是现代和过去海洋过程和变化的多功能示踪剂。它们通过大陆风化作用提供给海洋，因此提供了关于水团和陆源颗粒的来源和输送途径的信息，并提供了水库之间元素通量的估计（例如，沉积物/颗粒-海水交换）。这使得它们对于追踪其他微量元素的起源和命运特别有用，这些微量元素在海洋中扮演着微量营养素，示踪剂或污染物的重要角色。然而，由于缺乏数据，特别是来自太平洋的数据，我们对Nd同位素和稀土元素在不同海洋环境下的不同来源、汇和循环的理解迄今为止是有限的，这阻碍了它们作为海洋示踪剂的潜力的充分开发。拟议中的研究的目的是进行严格的调查溶解Nd同位素和稀土元素浓度分布沿着从韩国到斐济在西太平洋，将提供洞察控制这些分布的地球化学和物理过程。重点将放在以下关键目标上：1）直接比较水文和微量元素及同位素数据，以表征化学水团特征、它们沿沿着循环路径的演变以及这些特征与仅从水团混合预期的特征的偏差，从而提供对微量元素添加和交换过程的深入了解，2）源、汇、以及稀土元素和其它不易污染的微量元素（Ba、Tl、V、U、Mo、Re）在西太平洋的行为; 3）海洋沉积物中Nd同位素比值古档案的海水完整性验证。结果将有助于国际GEOTRACES计划的努力。

Neodymium isotopes and rare earth elements (REE) are versatile tracers for processes and changes in the modern and past ocean. They are supplied to the ocean by continental weathering and hence provide information on the source and transport pathways of water masses and terrigenous particles, and afford estimates of element fluxes between reservoirs (e.g., sediment/particle - seawater exchange). This makes them particularly useful for tracing the origin and fate of other trace elements that play important roles as micronutrients, tracers, or contaminants in the ocean. Yet, due to the scarcity of data, particularly from the Pacific Ocean, our understanding of the different sources, sinks, and cycling of Nd isotopes and REEs under different oceanic settings is so far limited, preventing a full exploitation of their potential as tracers in the ocean. The proposed study is designed to conduct a rigorous survey of the distribution of dissolved Nd isotopes and REE concentrations along a transect from South Korea to Fiji in the West Pacific that will afford insights into the biogeochemical and physical processes that control these distributions. The focus will be on the following key objectives: 1) direct comparison of hydrographic and trace element and isotope data for the characterization of chemical water mass signatures, their evolution along circulation pathways, and deviations of these signatures from those expected from water mass mixing alone, providing insight into trace element additions and exchange processes, 2) documentation and identification of sources, sinks, and the behavior of REEs and other non-contamination-prone trace elements (Ba, Tl, V, U, Mo, Re) in the West Pacific, and 3) verification of the seawater integrity of Nd isotope ratios in paleo-archives in marine sediments that are commonly used for the reconstruction of past ocean circulation. The results will contribute to the efforts of the international GEOTRACES program.