ETBC: Collaborative Research: Evaluating the Role of Submarine Groundwater Discharge in the Oceanic Nd Budget

关于海洋钕（Nd）收支仍有许多未解决的问题，这限制了我们对这种稀土金属的地球化学认识和对古海洋Nd同位素记录的解释。其中一个问题是Nd同位素比率与海洋中Nd浓度的明显不耦合，或所谓的“Nd悖论”，以及对流入海洋的Nd通量的大小和同位素组成的限制不足。杜兰大学和老道明大学的科学家根据初步数据假设，向海洋排放的海底地下水是平衡Nd收支所需的“缺失的Nd通量”的来源，这些通量也在控制海洋环境的Nd同位素组成方面发挥作用。为了验证他们的假设，科学家们计划从一系列排放到沿海海洋的地点获得地下水Nd浓度和同位素比率。所得数据将用于建立一个全球质量平衡模型，以确定测量到的Nd浓度和海底地下水排放的同位素比率是否足以平衡海洋Nd收支。该模型还将用于评估地下水Nd通量变化及其相关同位素组成对保存在含氢沉积物中的古海洋学Nd同位素记录的影响。至于更广泛的影响，这项研究的结果将被纳入两位科学家在各自大学所教授的课程中。作为该项目的一部分，杜兰大学的一名研究生和一名本科生以及老道明大学的一名研究生将得到支持和培训。

A number of unresolved questions remain concerning the oceanic neodymium (Nd) budget which limits our understanding of the geochemistry of this rare earth metal and the interpretation of the paleoceanographic Nd isotope record. Amongst the issues is the apparent uncoupling of Nd isotope ratios and Nd concentrations in the oceans, or the so-called 'Nd paradox', as well as poor constraint on the magnitude and isotopic composition of Nd fluxes to the oceans. Scientists from Tulane University and Old Dominion University, on the basis of preliminary data, hypothesize that submarine groundwater discharge to the ocean is the source of the 'missing Nd flux' required to balance the Nd budget, and that these fluxes also play a role in controlling the Nd isotopic composition of the marine environment. To test their hypothesis, the scientists plan to obtain groundwater Nd concentrations and isotope ratios from a range of locations that discharge to the coastal oceans. Resultant data would be used to develop a global mass balance model to determine whether measured Nd concentrations and isotope ratios of submarine groundwater discharge are sufficient to balance the oceanic Nd budget. The model would also be used to evaluate the impact of varying groundwater Nd fluxes, and their associated isotopic composition, on the paleoceanographic Nd isotope record preserved in hydrogenous sediments.As regards broader impacts, results from this research would be incorporated into classes taught by both scientists at their respective universities. One graduate student and one undergraduate student from Tulane University and one graduate student from Old Dominion University would be supported and trained as part of this project.