THE DISTRIBUTION AND BIOGEOCHEMISTRY OF TRANSITION METAL - ORGANIC COMPLEXES IN MARINE WATERS (CONNECTICUT, COPPER, IRON)

This thesis involves an investigation of the interaction between dissolved organic matter (DOM) and transition metals, particularly copper, in marine waters. Analytical techniques, including reverse phase liquid chromatography (C(,18)-RPLC), heated graphite atomizer atomic absorption spectrophotometry (HGA-AAS), and high performance liquid chromatography (HPLC), have been applied for the isolation, measurement, and characterization, respectively, of organically complexed metals dissolved in seawater. The geochemistry of copper and iron was studied in the estuarine waters of the Connecticut River, Connecticut, U.S.A. in July 1981. The organically complexed copper isolated by C(,18)-RPLC (Cu-organic) comprised 24 to 59% of the dissolved copper and was mostly conservative in the estuary and in laboratory estuarine mixing experiments. Riverine DOM, similar to terrigenous fulvic acid, was responsible for the observed copper complexation. The shelf and slope waters of the Middle Atlantic Bight were studied in July 1980. A significant fraction of the dissolved copper (9 - 60%) and smaller amounts of the dissolved nickel (0 - 8%) were complexed by DOM. The % Cu-organic was correlated with apparent oxygen utilization (AOU) indicating that biological production and consumption may considerably alter the copper speciation of seawater by forcing shifts in the carbonate equilibria and variations in pH. Riverine DOM was also responsible for the copper complexation observed in the Middle Atlantic Bight. The vertical distributions of dissolved copper and Cu-organic species were investigated during July 1980 in the Nothwestern Atlantic Ocean. Cu-organic species were present in all oceanic waters sampled and comprised 9 to 64% of the dissolved copper. The vertical distributions of Cu-organic were characterized by low concentrations in near surface waters, increasing to euphotic zone maxima at the depth of the seasonal thermocline and gradually increasing concentrations in deeper water. An equilibrium model, incorporating the complexation of copper by humic ligands, accounted for most of the Cu-organic measured analytically by C(,18)-RPLC in seawater collected from several Marine Ecosystem Research Laboratory (MERL) microcosms and the fraction of the copper organically complexed (26 - 40%) was dependent upon the pH and alkalinity in a predictable manner