Dating of sediment record at two contrasting sites of the Seine River using radioactivity data and hydrological time series.
Sediment cores were collected at the outlet of the highly anthropogenized catchment of the Seine River at two contrasting sites: a flood plain of the lower Seine River and a quasi-permanently submerged harbour basin (or wet dock) in the upper tidal estuary. Analyses of artificial radionuclides ((137)Cs and plutonium isotopes), coupled with hydrological and bathymetric data, lead to a precise dating of the sediment cores collected at the two sites. (137)Cs signals originating from global fallout (early 1960s) and from the Chernobyl accident (1986) are identified, but at different levels due to the incomplete nature or variable continuity of the records. Anomalous (238)Pu concentrations found at both sites (1-2 Bq kg(-1)) are attributed to unknown industrial releases originating from upstream. Interpolating (137)Cs sediment activities under the assumption of a constant sediment rate, those releases were dated back to 1975 ± 1, thus providing a local but reliable time-marker. Age models have highlighted a very contrasting sediment filling dynamics in these two sites. This study presents the first sediment record of alpha- and gamma-emitting artificial radionuclides obtained at the outlet of the huge catchment area of the River Seine, over a period covering the last 50 years.
Laboratoire de Radioécologie de Cherbourg-Octeville (LRC), IRSN, 50130 Cherbourg-Octeville, France; Université de Caen-Basse Normandie, Laboratoire M2C, UMR CNRS 6143, 14032 Caen, France.
Anne
A
Vrel
Dominique
D
Boust
Patrick
P
Lesueur
Julien
J
Deloffre
Carole
C
Dubrulle-Brunaud
Luc
L
Solier
Marianne
M
Rozet
Coralie
C
Thouroude
Catherine
C
Cossonnet
Sandrine
S
Thomas
D002588:Cesium Radioisotopes / Q000032:analysis; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000032:analysis*; D011005:Plutonium / Q000032:analysis; D045483:Rivers; D014875:Water Pollutants, Radioactive / Q000032:analysis
D002588:Cesium Radioisotopes; D014875:Water Pollutants, Radioactive; D011005:Plutonium
Dating; Flood plain; Isotope ratio; Sediment cores; Seine River; Upper estuary