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.
