THE DISTRIBUTION AND PERSISTENCE OF METAL CONTAMINANTS IN SURFACE SEDIMENTS OF THE NEW YORK BIGHT

Since the late 1800s, the apex of the New York Bight has served as a disposal site for wastes from the New York metropolitan area. Disposal of sewage sludge was terminated in 1987 and dredged sediment disposal is now restricted to cleaner sediments. To study the distribution and fate of inorganic contaminants associated with disposed materials, 440 surficial sediment grab samples (0-2 cm) were collected between 1993 and 2000 in the New York Bight apex. Sediment samples were analyzed for a suite of 35 major and trace elements, sediment texture, organic carbon, and Clostridium perfringens spores (a sewage indicator). Principal Components Analysis demonstrated a covariance of contaminant trace metals and C. perfringens spores with the distribution of fine-grained sediment. Enrichment factors were calculated by dividing the contaminant concentration by the observed natural background levels in order to study the extent of metal contamination in the Bight. Contaminant concentrations were up to 12 times natural background levels (e.g., 180 µg/g Pb) at both the dredge disposal site at the northwestern end of the Hudson Shelf Valley (HSV), and within the upper 20 km of the HSV. Each of these locations was dominated by fine-grained sediment. Enrichment calculations were normalized to fines and to organic carbon and still show enrichment (e.g., 2-4 times background levels for Cu). Comparison with data from sediments collected in the two years following cessation of sewage disposal (Zdanowicz ,1991) shows a decline in contaminant concentrations immediately adjacent to the sludge dumpsite (e.g., 150 to 30 µg/g Pb). However, concentrations in the upper HSV show a persistence of metal contaminants, some up to 9 times background values, in samples collected 11 years after the cessation of sewage sludge disposal.