River discharge of strong Cu-complexing ligands to south Atlantic bight waters

Discharge of dissolved organic matter (DOM) provides an important source of strong Cu-complexing ligands to the coastal ocean waters of Long Bay off the southeast coast of North Carolina. Concentrations of strong Cu ligands (SigmaL(i) at fixed K'(CuL) = 10(13.5)), measured using competitive ligand equilibration-cathodic stripping voltammetry with 8-hydroxyquinoline (8-HQ) as the competing ligand, were linearly correlated with dissolved organic carbon (DOC) concentrations (SigmaL(i)=0.23DOC-14, r(2)=0.81, pmuch less than0.01, n=9) in Long Bay transect samples. The relationship between SigmaL(i) and DOC measured in this study was very similar to that measured in a previous study for Cape Fear estuarine sites. The Cape Fear provides 1.8 x 10(6) Mol of Strong Cu ligands annually to Long Bay with a ratio of ligand/DOC of 1.7 x 10(-5) mol g(-1) C. For South Atlantic Bight (SAB) shelf waters, yearly discharge from organic-rich rivers may provide up to 1.7 x 10(7) Mol of strong Cu ligands. A river flux of this magnitude could support 1.6 nM strong Cu-complexation capacity throughout the SAB water column, or up to 50% of the total pool of strong Cu-complexing ligands. Estimates for the worldwide river discharge of terrestrial DOM indicate this source could support 0.03-0.2 nM strong Cu complexation capacity, or a maximum of 20% of the global ocean reservoir of strong Cu ligands. (C) 2004 Elsevier B.V. All rights reserved.