The Distribution of Dissolved and Organically Complexed Copper and Nickel in the Middle Atlantic Bight

Abstract

An analytical procedure involving C₁₈ reverse-phase liquid chromatography and heated graphite atomizer–atomic absorption spectroscopy was used to isolate and measure dissolved organically complexed copper and nickel along a section from the shelf–slope boundary into the New York Bight apex. The dissolved organic matter isolated by C₁₈ reverse-phase liquid chromatography was further separated and partially characterized by high-performance liquid chromatography. The distributions of dissolved copper and nickel were similar, with higher concentrations in the low-salinity surface waters and lower concentrations beneath the pycnocline and in slope waters. The concentration of total dissolved copper and nickel ranged from 0.77 to 8.67 nmol/kg and 2.3 to 14.7 nmol/kg, respectively. The concentrations of organically complexed copper (0.24–1.67 nmol/kg) increased uniformly across the shelf, with the highest concentrations at the New York Bight apex. A small percentage of the dissolved nickel (0–8%) was isolated as organically complexed nickel. The variation in the percentage of dissolved copper isolated as organically complexed copper (10–60%) was systematically related to other chemical properties and hydrographic features of the region. The organic components responsible for the copper complexation in these coastal waters are chromatographically similar to terrigenous fulvic acid and may originate in riverine waters.