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La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Small-scale spatial variations of natural radionuclide and trace metal distributions in sediments from the Hudson River estuary
Auteurs :	H. Feng, Auteur ; J. K. Cochran, Auteur ; D. J. Hirschberg, Auteur ; R. E. Wilson, Auteur
Type de document :	Article
Dans :	Estuaries (21(2) JUN 1998)
Article en page(s) :	263-280
Résumé :	Multiple sediment cores were collected in June 1994 in the turbidity maximum zone of the Hudson River estuary off Manhattan, New York. Results from X-radiography of the sediments and measurements of natural radionuclides ((234)Th, (7)Be, and (210)Pb) and trace metals (Ag, Cd, Cu, Pb, and Zn) show significant spatial variability of sediment composition and structure and patchy distributions of radionuclides activities and trace metal concentrations in this small area (0.6 km x 0.5 km). Radionuclide and trace metal analyses confirm prior work (Olsen et ai. 1978; Olsen et al. 1981; Hirschberg et al. 1996) that show the western margin area of the river acts as a repository of these chemical constituents at least for the short-term period (0.5-1 yr), and the midchannel area is not a depositional area for sediments and associated chemical constituents. (7)Be profiles reveal short-term sediment deposition rates ranging from 6 cm yr(-1) to 26 cm yr(-1) in the western margin area. Significant spatial variations in excess (234)Th and (7)Be inventories (up to a factor of 10 and 5 for (234)Th and (7)Be, respectively) are found in the western margin depositional area, although the inventories are balanced, on average, with in situ production in water column and atmospheric supply The spatial variation of surficial excess (210)Pb and trace metal concentrations in depositional areas of the western margin are less than or equal to 10% for Ag, Cu, Pb, and Zn and 29% for Cd. However, the variations in the transition zone range from 28% to 93%. This variability is likely related to variations in tidal current velocity, bottom shear stress, and river channel morphology.

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