Sedimentation dynamics in the East China Sea elucidated from Pb-210, Cs-137 and Pu-239,Pu-240

Sedimentation dynamics in the East China Sea was investigated based on prof iles and inventories of Pb-210(ex), Cs-137 and Pu-239,Pu-240 in sediment co res collected from various settings in this marginal sea. The derived sedim entation rates vary by two orders of magnitude, from similar to 2 to 0.02 c m yr(-1), and generally decrease southward along the inner shelf and eastwa rd offshore. This pattern is consistent with the dispersal of Yangtze River -derived sediments by the current and tidal systems. The weighted mean sedi mentation rate over the shelf (ca. 0.3 g cm(-2) yr(-1)) appears to be highe r than fluvial inputs from the Yangtze River and Taiwan (0.14 g cm(-2) yr(- 1)). The discrepancy can be reduced by considering the effect of sediment m ixing (which renders sedimentation rates overestimated) and the possibility of additional sediment input from the Yellow River's dispersal system. Spa tial variations of the observed nuclide inventories in sediments suggest ex tensive sediment redistribution, boundary scavenging of Pb-210, and large i nputs of Cs-137 and Pu-239,Pu-240 from Yangtze River's drainage basin. (C) 1999 Elsevier Science B.V. All rights reserved.