Willey, J. D., U North Carolina Wilmington, Wilmington, NC, USA, willeyj@uncw.edu
Kieber, R. J., U North Carolina Wilmington, Wilmington, NC, USA, kieberr@uncw.edu
Seaton, P. J., U North Carolina Wilmington, Wilmington, NC, USA, seatonp@uncw.edu
Miller, C. ., U North Carolina Wilmington, Wilmington, NC, USA, millerc@uncw.edu

RAINWATER: AN EPISODIC SOURCE OF PHOTOCHEMICALLY REACTIVE IRON TO SURFACE SEAWATER

Rainwater hydrophobic extractable dissolved organic matter (EDOM) contains ligand(s) that prevent Fe(II) oxidation for at least four hours after mixing with seawater. The EDOM Fe(II) complex is at least as strong as the Fe(II) ferrozine complex, making it the strongest Fe(II) ligand observed in natural waters. EDOM occurs even in very low organic content marine rain and does not have the same chemical composition or chromophoric properties as EDOM collected from the nearby Cape Fear River. Photochemical experiments demonstrate that iron complexed with EDOM accurately mimics the diurnal cycling of Fe in rainwater. During the day photoreduction of Fe(III)EDOM predominates, while at night a fraction of the photochemically produced Fe(II) oxidizes to Fe(III). EDOM complexed Fe(II) resists oxidation. Photochemical production of Fe(II) from EDOM can be predicted using the same model developed for this prediction in authentic rain. In addition to its central role in redox reactions occurring in the troposphere, the stability of EDOM complexed Fe(II) is important because it directly affects the bioavailability of rainwater-derived Fe in the surface ocean.

Oral presentation

Presentation is given by student: No
Session #:SS01
Date: Friday, June 13, 2008
Time: 11:30 AM

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