| Popis: |
High precision measurements of natural uranium isotopes in the Atlantic Ocean, Mediterranean Sea,and Black Sea reveal isotopic makeups which differ significantly from the well-known oceaniccomposition. In the Mediterranean, water masses are strongly differentiated to the extent that theyare able to be fingerprinted on the basis of δ234U. Mediterranean deep water masses show thehighest enrichment, with an offset with respect to oceanic δ234U values of just over 1 ‰. The BlackSea shows an even higher offset of up to ~40 ‰.This offset provides an opportunity to look into the as of yet largely unstudied uranium inputs to theMediterranean, in particular rivers and submarine groundwater discharge (SGD), which are thoughtto play key roles in uranium input to the global ocean. A simple box model, incorporating theMediterranean and Black Sea data from this study is constructed to provide a first estimate of the Uconcentration and δ234U signature of rivers and SGD necessary for this offset to arise. Theseestimates are then compared with new measurements of various coastal and submarine springs fromalong the French Mediterranean Coast as well as with existing riverine data exists to speculate onwhich inputs may be most responsible for this offset. |
