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Photochemical Degradation of Strong Natural Iron-Binding Ligands in the California Current Ecosystem

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Randelle Bundy
Kathy Barbeau

The speciation of iron has been shown to be significantly affected by photochemical processes in the surface ocean, altering both the redox state and organic complexation of iron. The effects of photochemistry on natural iron-binding ligands were examined in the California Current Ecosystem on subsurface water masses. Changes in the iron-binding ligand pool were measured using competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-ACSV) at several competition strengths in order to probe changes in both the strong and weak ligand classes. Preliminary results suggest that strong ligands are significantly altered upon exposure to natural light. Light treatments showed a significant decrease in conditional stability constants and a large increase in weak iron-binding ligand concentrations, only perceptible at the lowest competition strengths. Dark treatments remained relatively unchanged compared to initial conditions. The fact that such changes in the ligand pool were not readily detectable at all analytical windows suggests the utility of using multiple analytical windows for mechanistic iron-binding ligand studies.

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Background Photo by: Nicole Hansen - Jornada (JRN) LTER