Soluble and Colloidal Iron-Binding Organic Ligands in the Surface Water of Subtropical North Atlantic and North Pacific Oceans

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OCE-0220978A PI from the University of Alaska plans to measure concentrations of Fe and Fe-binding ligands in the soluble (0.02 um) and the colloidal phase (0.02-0.4 um) of surface waters from the BATS and HOT regions to understand the chemical and physical speciation of Fe. Samples will be separated into the soluble and colloidal phase using a new microfiltration technique developed by the PI. Iron concentrations will be measured by an isotope dilution-high resolution inductively coupled plasma mass spectrometry microanalytical method. The thermodynamic stability constants and kinetic rate constants of Fe-complexing natural ligands in the soluble and colloidal phases will be determined by the competitive ligand equilibration/cathodic stripping voltammetric method. The PI also plans to assess the spatial and temporal variability of these parameters at these two sites. Results from this study will provide useful constraints for models to determine the biological availability of soluble and colloidal Fe, the fate of Fe from dust inputs to the surface ocean and the Fe limitation on nitrogen fixation.