Many reactive pollutants, such as Zn, Cu, Pb, Cs-137, Pu-239, 240 and PCB's appear to be transported and accumulated together in association with fine-grained particles in the Hudson River estuary. Anthropogenic increases of 3-6 times natural levels of Zn, Cu, and Pb were found for Hudson sediments. Mobilization of Cd and Ni in the sediments of a small embayment of the Hudson with very high contamination levels appears to be primarily by resuspension of fine particles, although elevated concentrations of Cd in pore waters were also observed. Radiocarbon measurements indicate the predominant source of organic carbon in New York harbor sediments is recent sewage and not petroleum hydrocarbon contamination. A new enzymatic technique was developed to trace the distribution of cellulose, a significant component of sewage sludge, in coastal sediments. Radon-222, a natural radioactive gas dissolved in the Hudson, is supplied primarily from the sediments at approximately twice the rate predicted by molecular diffusion. The behavior of phosphate and trace metals derived from sewage was examined on the basis of field data and the use of simple models to examine management alternatives. The most reasonable course appears to be completion of secondary sewage treatment plants in New York City and major upgrading of primary treatment in New Jersey.