The dynamics of ⁶⁰Co- labelled sediment particles in the Seine estuary

¹ Laboratoire d'Études Radioécologiques de la Façade Atlantique, IPSN, Octeville, France
² Laboratoire Morphodynamique Continentale et Côtière, UPRES A 6143 du CNRS, Université de Caen, France
³ Service de la Navigation de la Seine, Port Autonome de Rouen, France

Abstract

From 1990 to 2000, ⁶⁰Co, a radionuclide released into the English Channel by the La Hague reprocessing plant, has been measured in the deposited sediments of the Seine estuary. Since 1990, the ⁶⁰Co concentrations have slowly increased from some tenths of Bq.kg^-1 to ca 10 Bq.kg^-1. This transient signal was used to bring the evidence of the input of marine particles far upstream in the estuary, ca 80 km from the river mouth. The dynamics of this process have been deciphered by comparing several sets of data obtained in the years 1990 to 2000. An average velocity of about 10 km.y^-1 was found for this incoming sediment pool. These observations are conformable with calculated of suspended sediment fluxes performed along the river.