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

关于大洋钕(ND)的预算仍有许多悬而未决的问题，这限制了我们对这种稀土金属的地球化学的理解和对古海洋ND同位素记录的解释。其中一个问题是，海洋中的ND同位素比率和ND浓度明显脱钩，即所谓的“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很差。杜兰大学和老道明大学的科学家根据初步数据假设，海底地下水向海洋排放是平衡ND收支平衡所需的“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，科学家们计划从排放到沿海海洋的一系列地点获得地下水的ND浓度和同位素比率。所产生的数据将被用来开发一个全球物质平衡模型，以确定海底地下水排放的测量的ND浓度和同位素比率是否足以平衡海洋的ND收支。该模型还将用于评估不同的地下水ND通量及其相关的同位素组成对保存在水文沉积物中的古海洋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教授的课程。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多米尼恩大学的一名研究生将得到支助和培训。

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.