南中国海岩质输入对Nd循环的影响：基于水柱不同深度海水中稀土元素浓度及浮游有孔虫中Nd同位素组成的研究。

本研究项目通过调查海水中钕的同位素组成，以了解海洋环流与岩源输入对钕循环的影响。研究利用沉积物捕集器采集浮游有孔虫，旨在评估钕同位素随季节的变化及其对南海海水化学特性的影响。要求具备地球化学或地质学方面的背景知识。

Job description: Project description: The isotopic composition of dissolved neodymium (143Nd/144Nd, expressed as εNd) in seawater is a valuable tracer of both ocean circulation and lithogenic Nd inputs associated with continental weathering. The εNd of the modern ocean exhibits strong spatial heterogeneity, related to the relatively short residence time of Nd (500–1000 years) compared with the global ocean mixing time (~1500 years). Its distribution is controlled by several processes, including fluvial and aeolian lithogenic inputs, particle scavenging and desorption in the water column, so-called “boundary exchange” processes, and benthic fluxes associated with early diagenesis of sediments. However, the impact of these external inputs, particularly sediment–seawater interactions, remains poorly constrained. This knowledge gap limits our understanding of the modern Nd cycle and the use of εNd as a tracer of water-mass mixing and continental weathering inputs, both in modern oceanographic and palaeoceanographic studies. Planktonic foraminifera are widely used to reconstruct past variations in ocean circulation. Several studies have shown that foraminifera recovered from surface sediments primarily record the εNd composition of deep and/or pore waters. The initial seawater isotopic signature can indeed be modified by Fe–Mn oxide coatings formed below the sediment–water interface. Recent studies using sediment traps have nevertheless shown that the εNd incorporated into Fe–Mn oxide coatings on foraminiferal tests may also be modified during their descent through the water column. Seasonal variations in seawater εNd associated with fluctuations in sediment inputs have notably been observed in the Bay of Bengal and the Philippine Sea. These variations provide evidence for rapid (seasonal-scale) exchanges between lithogenic particles and seawater, particularly when particulate inputs are high, and are influenced by the mineralogy and degree of weathering of terrigenous material. Local lithogenic inputs may therefore exert a significant influence on seawater εNd in marginal seas, yet high-resolution data covering different seasons remain scarce. The South China Sea (SCS), a semi-enclosed marginal sea of the Pacific Ocean, provides an ideal setting for disentangling the effects of ocean circulation from those of lithogenic Nd inputs. Pacific Deep Water (PDW; εNd ~ −4) enters the SCS through the Luzon Strait and continuously ventilates its deep basin. As it flows along the northern and western margins of the SCS, the PDW may be modified by substantial sediment inputs from major Asian rivers, including the Pearl River, Red River, and Mekong River, which are characterized by contrasting εNd values (−11 to −13). This study will investigate rare earth element (REE) concentrations and Nd isotopic compositions in seawater samples and planktonic foraminifera collected at different depths using sediment traps along a north–south transect in the SCS. The objectives are to: (i) better constrain the distribution of εNd and REE concentrations along the pathway of PDW on the western margin of the SCS, particularly in the central and southern regions, which remain poorly documented; (ii) characterize the Nd isotopic signatures preserved in modern planktonic foraminifera collected using sediment traps; (iii) assess the impact of seasonal variations in lithogenic inputs on seawater εNd throughout the water column; and (iv) improve our understanding of the preservation of the Nd isotopic signature of foraminifera in marine sediment cores.

所需个人背景与技能要求： 申请者需具备地球化学与地质学方面的知识。对古气候学和/或海洋沉积地质学技能亦备受重视。申请者将需在多个分析平台上工作，并运用各种尖端技术获取研究结果。申请者还需进行文献研究，撰写摘要与论文，并具备较高的英语水平。 所需英语水平：基础级。如果您与交流者能够轻声清晰地沟通，您便能够在基本的日常场景中理解语言。您能够理解并使用简单的表达方式。