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Dissolved organic copper and chromium complexes were measured in both overlying and interstitial waters of Narragansett Bay and mesocosm sediments using C18 reverse-phase liquid chromatography and atomic absorption spectroscopy. In the interstitial and overlying waters, the isolation procedure recovered 22–67% of the total dissolved copper, 23–55% of the total dissolved chromium and 14–40% of the dissolved organic carbon. The distribution of both total and organic copper decreased with depth in the cores and exhibited a subsurface maximum near the zero Eh level (z = 2–4 cm). Below that depth, both forms of copper continued to decrease until an apparent equilibrium with sulfide minerals was established (7–8 cm). Dissolved chromium exhibited a different geochemistry, with both total and organic chromium increasing in concentration with depth in the cores, possibly due to remobilization from some mineral phase such as chromic hydroxide or chromite.

The geochemistry of dissolved copper-organic complexes was investigated in the estuarine waters of Narragansett Bay. A transect survey was conducted in August 1980, while one mid-bay station was monitored from March through August of that year. The transect data indicated that most of the copper-organic complexes enter the bay via sewage effluent which is discharged into the Providence River at the head of the bay. Organic copper concentrations in the estuary ranged from 0.12 to 2.30 μg kg−1 and comprised from 14 to 70% of the total dissolved copper. The concentration of copper-organic complexes was not directly related to the amount of dissolved organic matter; and recently generated organic material from phytoplankton production within the bay had a negligible influence on the fraction of dissolved copper which was organically bound. The major source of total copper to the bay is anthropogenic inputs from sewage effluents. Particulate and dissolved copper concentrations ranged from 0.06 to 2.42 and 0.23 to 16.4 μg kg−1, respectively, giving average values of about 40% particulate and 60% dissolved copper. Particulate copper concentrations decreased rapidly from the upper to the lower bay as a result of both removal and dilution. About 75% of the dissolved copper entering the bay is rapidly removed in the Providence River and upper bay, and the remaining portion (which is largely organic copper) follows conservative mixing in the mid to lower bay. The data suggest that copper binding by dissolved organic matter may be an important control on the riverine flux of dissolved copper through estuaries into coastal and oceanic waters.

Dissolved organic matter (DOM) and dissolved copper-organic complexes were isolated from the estuarine waters of Narragansett Bay, RI, using reverse-phase liquid chromatography employing C18 Sep-Pak cartridges (Waters Associates). The cartridges were found to have a constant retention efficiency for processing ⩽ 1-l volumes of seawater. Fractionation of the isolated material, by sequential elution of the Sep-Pak with water: methanol mixtures of increasing organic solvent concentration, yielded a fraction of the organic matter with a specific copper activity six times greater than the overall activity for the isolated DOM. Analysis of this fraction by high performance liquid chromatography suggested that the organic components are of intermediate polarity and have appreciable aromatic character. An investigation of the protonation characteristics of the isolated complexes indicated that most of the copper is associated with a broad range of acidic sites on the DOM. Analysis by electron paramagnetic resonance spectroscopy confirmed the organic association of the isolated copper and also suggested the presence of several types of binding sites which probably involve oxygen donor ligands. Studies of the exchange of 64Cu with these binding sites on the isolated DOM indicated that 70% of the sites undergo rapid exchange with copper in seawater while 20% of these sites did not exchange in a 24-h time period.

Reverse-phase liquid chromatography was used for the isolation of dissolved organic matter and dissolved copper-organic complexes from the estuarine waters of Narragansett Bay, Rhode Island. The procedure isolates 10–30% of the organic matter and up to 50% of the total dissolved copper from various bay samples. Chromatograms obtained by high-performance liquid chromatography of the isolated organic matter showed qualitative differences between sampling stations progressing from the Providence River in the upper bay to the lower bay.

Dissolved organic matter (DOM) and dissolved copper-organic complexes were isolated from the estuarine waters of Narragansett Bay, RI, using reverse-phase liquid chromatography (RPLC). Different types of reverse-phase BOND ELUT columns (Analytichem International), including C 2 , C 18 and phenyl-bonded phases, were studied to determine their adsorption efficiency for extracting DOM. Extraction efficiencies followed the order phenyl > C 18 > C 2 , and phenyl − C 18 > C 2 for DOM and organic copper, respectively. However, comparisons of BOND ELUT and C 18 SEP-PAK (Waters Associates) columns indicated that SEP-PAK columns were the most efficient when both DOM and organic copper were considered. Chromatographic profiles of the isolated DOM obtained using high-performance liquid chromatography were similar in elution characteristics and resembled chromatograms typical of fulvic acid. The UV-absorption characteristics of the DOM showed small differences and suggested that the different reverse-phase columns isolated material that was qualitatively similar. Copper-organic complexes isolated using C 18 RPLC were studied to examine the dissociation of organically bound copper in seawater as the pH is lowered. Only a small amount of the complexed copper was displaced by the H + with about 40% of the copper remaining bound at pH 3. However, the chromatographic elution behavior of the DOM and organic copper was significantly altered under acidic conditions as a result of protonation of acidic functional sites on the organic matter.

The upper region of the Pettaquamscutt River, Rhode Island, is a fjord-type estuary with two deep basins separated by a shallow sill. The water column in these basins remains stable for periods of several years with only partial mixing occurring. Dissolved organic copper isolated by C18 reverse-phase extraction was determined in the uppermost basin; these values ranged from 0.29 μg kg−1 in the oxic surface waters to