Dissolved organic copper isolated by C18 reverse-phase extraction in an anoxic basin located in the Pettaquamscutt River Estuary

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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 <0.001 μg kg-1 in the deeper anoxic waters. Total dissolved and particulate copper concentrations ranged from 0.53 to 0.13 μg kg-1 and 0.46 to <0.03 μg kg-1, respectively. Dissolved concentrations were highest at the surface while particulate copper values were greatest in the suboxic deeper waters. Organically bound copper accounted for 42-60% of the total dissolved copper in the oxic surface waters; however, these values progressively decreased to < 1% through the redox transition zone. Chromatographic profiles of isolated dissolved organic matter were obtained using high-performance liquid chromatography. These profiles indicate that dissolved organic matter (DOM), which complexes copper in oxic waters, is present in the suboxic region. However, binding of copper by this fraction of DOM is reduced or eliminated by competition with dissolved sulfide complexes. © 1989.

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Marine Chemistry