Radionuclide Indicators of Sediment Dynamics in the Delaware Estuary
Date
2012-10-09
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Abstract
This report describes the methods and results of a seasonal study of suspended sediment dynamics in the Delaware Estuary using radionuclides as sediment tracers. Specifically, Be-7, I-131, and Pb-210 were used to determine if the estuary at selected coring sites was depositional, and if so, what were the rates of recent deposition. Be-7/Pb-210xs ratios were used to determine relative ages, or time since the sediment was in contact with the water column. Cores from eight sites in the middle to lower estuary were collected in summer, fall, and winter of 2011. Deposition rates varied among coring sites and over time. The absence of Be-7 and I-131 in bed deposits suggest that the estuary at the sampling locations is experiencing no net accumulation. An analysis of deposition variations among cores between seasons suggests large freshwater discharges following Hurricane Irene and Tropical Storm Lee moved the usual depositional zone about 50 kilometers seaward to the lower estuary. Iodine-131 was used to determine general transport distances since it is only sourced in the urbanized estuary.
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Keywords
Delaware Estuary, radionuclide indicators, sediment