THE DISTRIBUTION OF SEWAGE SLUDGE, TRACED BY ELEVATED SILVER AND COPPER CONCENTRATIONS, ALONG THE HUDSON SHELF VALLEY

The Hudson Shelf Valley (HSV), located off the coast of New Jersey and south of Long Island, is a submerged extension of the Hudson River, cutting into the shallow sloping continental shelf. The 12-Mile Dump Site located on the shelf adjacent to the head of the HSV was the site of sludge dumping until about 1987. Elevated concentrations of metals, bacteria, carbon, and organic contaminants can be measured as far as 60km down the valley from the dumpsite. After the sludge dumping ban in 1987, sources of anthropogenic material have remained, such as urban runoff and atmospheric deposition. Ten cores along the axis of the valley and seven cores in a transect 10km south of the dumpsite, were selected to examine the effects of sludge dumping. Silver (Ag) and copper (Cu) were selected from a suite of 35 elements to serve as anthropogenic tracers. Ag and Cu both have primarily anthropogenic sources, Ag from photo developing and X-ray synthesis, and Cu from plumbing hardware. The highest concentrations of Ag and Cu are found in cores taken in a transect down the axis of the HSV, with Ag peaks at 9.02µg/g and Cu at 552.3µg/g. The average background concentration for Ag in cores from the New York Bight is 0.42µg/g, and Cu background values were measured at 10µg/g in similar cores. The cores taken in a transect across the valley show that Ag and Cu concentrations are high in the center of the valley (Ag concentrations reach 5.0µg/g, and Cu concentrations reach 530µg/g) but background values are recorded for both Ag and Cu at the edges of the valley. These observations show potential movement of the sediment away from the dumpsite, with accumulation occurring in the upper part of the HSV.