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IPY-OSC Francisco Fernandoy-46
APECS is an international and interdisciplinary organization for undergraduate and graduate students, postdoctoral researchers, early faculty members, educators and others with interests in Polar Regions and the wider cryosphere. Our aims are to stimulate interdisciplinary and international research collaborations, and develop effective future leaders in polar research, education and outreach. We seek to achieve these aims by:
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KitaeKim2010aAuthor(s):
Kitae Kim*, Wonyong Choi*, Michael R. Hoffmann**, Ho-Il Yoon***, Byong-Kwon Park***

*School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea **W. M. Keck Laboratories, California Institute of Technology, Pasadena, CA, USA ***Korea Polar Research Institute, Incheon, Korea

Originally Presented at:
IPY Oslo Science Conference, Oslo, Norway 8-12 June 2010

Abstract:
The availability of iron has been thought as a main limiting factor for the phytoplankton productivity and related with the uptake of atmospheric CO2 and algal blooms in fresh and sea waters. In this work, the formation of bio-available iron (Fe(II)aq) from the dissolution of iron oxide particles was investigated in ice phase under both UV and visible light irradiation. The photoreductive dissolution of iron oxides proceeded slowly in aqueous solution (pH 3.5) but was significantly accelerated in polycrystalline ice with subsequently releasing more bioavailable ferrous iron upon thawing. The enhanced photogeneration of Fe(II)aq in ice was confirmed regardless of the type of iron oxides [hematite, maghemite (?-Fe2O3), goethite (?-FeOOH)] and the kind of electron donors. The ice-enhanced dissolution of iron oxides was also observed under visible light irradiation although the dissolution rate was much slower compared with the case of UV radiation. The iron oxide particles and organic electron donors (if any) in ice are concentrated and aggregated in the liquid-like grain boundary region (freeze concentration effect) where protons are also highly concentrated (lower pH). The enhanced photodissolution of iron oxides should occur in this confined boundary region. We hypothesized that electron hopping through the interconnected grain boundaries of iron oxide particles facilitates the separation of photoinduced charge pairs. The outdoor experiments carried out under ambient solar radiation of Ny-Alesund (Svalbard, 78.55 N) also showed that the generation of dissolved Fe(II)aq via photoreductive dissolution is enhanced when iron oxides are trapped in ice. Our results imply that the ice(snow)-covered surfaces and ice-cloud particles containing iron-rich mineral dusts in the polar and cold environments provide a source of bioavailable iron when they thaw.

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