Suspended Particulate Matter in the New York Bight Apex, Fall 1973

Abstract

ABSTRACT Four surveys of suspended particulate matter in the New York Bight apex from September through November 1973 revealed consistent distributions that reflect the water circulation. Two major currents were dominant during the fall season of limited river flow and gradually weakening stratification of the water column: (1) low-salinity (29 to 31) surface water, containing between 1 to 4 mg/l of suspended particles, flows from Hudson estuary southward along the New Jersey coast within 5 to 10 km from shore; and (2) northward flow along Hudson shelf channel occurred during all surveys. Low concentrations of total suspended matter and ash fractions dominated by diatoms indicate a central shelf origin for the shelf-channel current. The distribution of total suspended matter and the dispersion patterns of iron particles released at the acid-waste dumpsite support the existence of a clockwise gyre in the central part of the area during autumn; the shelf-channel current forms the western limb of this gyre. Dredge spoil and sewage sludge dumped near the head of the shelf channel settle into this depression to form mud lenses rich in organic matter. Some of this material is entrained into a turbid bottom layer by the northward current and transported from the depression to the northeast over Cholera Bank. The bank crest does not accumulate fine sediment owing to relatively vigorous wave surge. As the turbid current turns south along the east side of Cholera Bank, fine-grained, mineral and organic material begins to s ttle, forming two disconnected lenses of mud on either side of the sand bank. Contaminated sediments are widely dispersed throughout the water column in the bight apex. Major dispersion appears to be centered on the Hudson shelf channel, and there is good evidence that material dumped near the channel head is transported up and down the channel in substantial quantities.