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Photoreductive Dissolution of Iron Oxides Trapped in Ice and Its Environmental Implications

Kim, Kitae and Choi, Wonyong and Hoffmann, Michael R. and Yoon, Ho-Il and Park, Byong-Kwon (2010) Photoreductive Dissolution of Iron Oxides Trapped in Ice and Its Environmental Implications. Environmental Science and Technology, 44 (11). pp. 4142-4148. ISSN 0013-936X.

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The availability of iron has been thought to be a main limiting factor for the productivity of phytoplankton and related with the uptake of atmospheric CO_2 and algal blooms in fresh and sea waters. In this work, the formation of bioavailable iron (Fe(II)_(aq)) from the dissolution of iron oxide particles was investigated in the 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, 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 (γ-Fe_2O_3), goethite (α-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-Ålesund (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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Hoffmann, Michael R.0000-0001-6495-1946
Additional Information:© 2010 American Chemical Society. Received December 14, 2009. Revised manuscript received April 15, 2010. Accepted April 20, 2010. Publication Date (Web): May 6, 2010. Funding for this work was provided by KOSEF NRL program (No. R0A-2008-000-20068-0), KOSEF EPB center (No. R11-2008-052-02002),KCAP (Sogang Univ.) funded by NRF(2009-C1AAA001-2009-0093879), and Korea Polar Research Institute (KOPRI). K.K. thanks J. Klanova and P. Klan for their kind support of his visit and training at Masaryk University, Czech Republic. We gratefully acknowledge the contributions of D. Hrazdira and Y. Ahn.
Funding AgencyGrant Number
Korea Science and Engineering Foundation (KOSEF)R0A-2008-000-20068-0
Korea Science and Engineering Foundation (KOSEF)R11-2008-052-02002
National Research Foundation of Korea2009-C1AAA001-2009-0093879
Korea Polar Research Institute (KOPRI)UNSPECIFIED
Masaryk University, Czech RepublicUNSPECIFIED
Issue or Number:11
Record Number:CaltechAUTHORS:20100617-080853893
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Official Citation:Photoreductive Dissolution of Iron Oxides Trapped in Ice and Its Environmental Implications Kitae Kim, Wonyong Choi, Michael R. Hoffmann, Ho-Il Yoon, Byong-Kwon Park Environmental Science & Technology 2010 44 (11), 4142-4148
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:18715
Deposited By: Tony Diaz
Deposited On:09 Jul 2010 21:33
Last Modified:03 Mar 2020 13:01

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