Dynamics of sediment and contaminant transport in the Hudson River estuary: Evidence from sediment distributions of naturally occurring radionuclides

Near surface (< 10 cm) sediment distributions of ²³⁴Th sampled multiple times at five locations along the axis of the Hudson Estuary from the Upper Bay of New York to Haverstraw Bay are compared with ²¹⁰Pb data from longer cores at the same locations. The comparison indicates that while there is little net sediment accumulation anywhere except at one location in the Upper Bay, near surface sediment in this reach of the estuary is mobile on short (months) time scales. The sediment appears to be physically mixed rather than bioturbated. Comparison of the sediment inventories of ²³⁴Th with calculated water column production indicates short time scale (months) variability in ²³⁴Th deposition. Some parts of the bottom have ²³⁴Th inventories in excess of local production but these appear to be balanced by ²³⁴Th deficient area, resulting in a general equilibrium. Sediment inventories of Pb, Cu, and Zn normalized to ²¹⁰Pb show no evidence of a uniquely urban source of these metals to the lower estuary. Silver distributions in sediment indicate a possible source of silver from New York City, probably related to sewage inputs.