Effect of ocean dumping on 13C/12C ratios in marine sediments from the New York Bight

In order to evaluate the influence of the ocean dumping of sewage sludge upon the organic carbon fraction of sediments of the New York Bight, a study of carbon isotopic variations in surface sediments from the area has been completed. On the basis of our ¹³C/¹²C measurements, it appears that: (1) sewage is depleted in ¹³C as compared to average marine organic sedimentary carbon, and (2) δ¹³C values from sediments of the New York Bight show systematic variations which are a direct consequence of the sludge disposal. Based on assumptions regarding inputs of sedimentary carbon to the sea floor in this area, we have modeled these ¹³C/¹²C variations in terms of progressive dilution of normal marine carbon with carbon derived from the ocean dumping of wastewater sludges. The isotopic composition of carbon in sediments from the New York Bight may serve as a quantitative tracer of sewage sludge components.