La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

Titre :	Annual cycle of radionuclide contamination on tide-washed pasture in the Mersey Estuary, NW England
Auteurs :	M. S. Johnson, Auteur ; D. Copplestone, Auteur ; W. M. Fox, Auteur ; S. R. Jones, Auteur
Type de document :	Article
Dans :	Estuaries (24(2) APR 2001)
Article en page(s) :	198-203
Résumé :	The radionuclide burden of vegetation comprising a tide-washed pasture at Ince Marsh in the Mersey Estuary; U.K., derives mainly from adhered external particulates originating as suspended sediments in estuarine water. Radionuclide concentrations are dominated by the growth cycle of the vegetation, with the highest winter levels of contamination activity an order of magnitude greater than the lowest levels in mid-summer. A secondary effect due to sediment transfer during periods of severe flooding produces subsidiary features on this dominant seasonal profile. Radionuclide concentrations on vegetation are in the range (137)Cs = 8-191, (134)Cs = 0.3-0.9, (241)Am = 0.6-46, (238)Pu = 0.1- 15, and (239,240)Pu = 0.8-44 Bq kg(-1). These ranges reflect the relative concentrations of radionuclides in estuarine sediment ((137)Cs = 615) (241)Am = 202, and (239/240)Pu = 104 Bq kg(-1)) rather than the values in filtered estuary water ((137)Cs = 0.4) (241)Am = 0.001, and (239/240)Pu = 0.001 Bq l(-1)). Median K(d) values for these radionuclide species are Cs = 1,400, Am = 200,000, and Pu = 80,000 I kg(-1)).

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