Distribution and inventories of some artificial and naturally occurring radionuclides in medium to coarse-grained sediments of the channel

• Published in: Continental shelf research Vol. 19; no. 15; pp. 1959 - 1975
• Main Author: Boust, Dominique
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.1999
• Subjects: Artificial radionuclides; Clastic sediments; English Channel; FLUXMANCHE II; Inventory; Marine; Naturally occurring radionuclides; Northwest European Shelf; ANE, Europe, English Channel; Naturally occurring radionuclides; FLUXMANCHE II; Artificial radionuclides; English Channel; Northwest European Shelf; Inventory; Clastic sediments
• ISSN: 0278-4343; 1873-6955
• DOI: 10.1016/S0278-4343(99)00048-5

Concentrations of artificial ( 60 Co, 137 Cs, 238 Pu and 239,240 Pu ) and naturally occurring radionuclides ( 40 K, 212 Pb and 214 Pb , daughter nuclides of the 232 Th and 238 U series) in bottom sediments of the Channel are reported. They are grain-size modulated but usual grain-size normalisation methods fail due to the strong heterogeneity of the sediment admixture and/or the occurrence of rock debris in the area of concern. When plotted versus distance from Cap La Hague, 60 Co and Pu isotope concentrations display a maximum in the Central Channel, but 137 Cs do not. This is further explained by the contribution of the releases from the La Hague plant relative to other radionuclide inputs, especially Atlantic inflow and direct atmospheric fallout. Apparent transit times from Cap La Hague are derived from Pu isotopic ratios and yield average sediment velocities ranging from some kilometres to some tens of kilometres per year. Sediment inventories of artificial radionuclides show that a significant part of the input of 60 Co and Pu isotopes is immobilised in the Channel seabed while most of the 137 Cs input has been evacuated by water mass circulation.