title: Rapid neodymium release to marine waters from lithogenic sediments in the Amazon estuary.
abstract: Rare earth element (REE) concentrations and neodymium isotopic composition (ɛNd) are tracers for ocean circulation and biogeochemistry. Although models suggest that REE release from lithogenic sediment in river discharge may dominate all other REE inputs to the oceans, the occurrence, mechanisms and magnitude of such a source are still debated. Here we present the first simultaneous observations of dissolved (<0.45 μm), colloidal and particulate REE and ɛNd in the Amazon estuary. A sharp drop in dissolved REE in the low-salinity zone is driven by coagulation of colloidal matter. At mid-salinities, total dissolved REE levels slightly increase, while ɛNd values are shifted from the dissolved Nd river endmember (-8.9) to values typical of river suspended matter (-10.6). Combining a Nd isotope mass balance with apparent radium isotope ages of estuarine waters suggests a rapid (3 weeks) and globally significant Nd release by dissolution of lithogenic suspended sediments.
authors.affiliation: GET, Université de Toulouse, CNRS, IRD, CNES, 14 Avenue Edouard Belin, Toulouse F-31400, France.
authors.forename: Tristan C C
authors.initials: TC
authors.lastname: Rousseau
authors.affiliation: GET, Université de Toulouse, CNRS, IRD, CNES, 14 Avenue Edouard Belin, Toulouse F-31400, France.
authors.forename: Jeroen E
authors.initials: JE
authors.lastname: Sonke
authors.affiliation: GET, Université de Toulouse, CNRS, IRD, CNES, 14 Avenue Edouard Belin, Toulouse F-31400, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Chmeleff
authors.affiliation: LEGOS, Université de Toulouse, CNRS, IRD, CNES, 14 Avenue Edouard Belin, Toulouse F-31400, France.
authors.forename: Pieter
authors.initials: P
authors.lastname: van Beek
authors.affiliation: LEGOS, Université de Toulouse, CNRS, IRD, CNES, 14 Avenue Edouard Belin, Toulouse F-31400, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Souhaut
authors.affiliation: Universidade De Brasilia, UNB, LAGEQ, Campus universitário Darcy Ribeiro, Brasilia, DF 70.910-900, Brazil.
authors.forename: Geraldo
authors.initials: G
authors.lastname: Boaventura
authors.affiliation: Hydrosciences Montpellier, Université de Montpellier-IRD-CNRS, Place Eugène Bataillon 34000, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Seyler
authors.affiliation: LEGOS, Université de Toulouse, CNRS, IRD, CNES, 14 Avenue Edouard Belin, Toulouse F-31400, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Jeandel