Accelerated dissolution of iron oxides in ice D. Jeong1,*, K. Kim1,*, and W. Choi1 1School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790–784, Korea *These authors contributed equally to this work.
Abstract. Iron dissolution from mineral dusts and soil particles is vital as a source
of bioavailable iron in various environmental media. In this work, the
dissolution of iron oxide particles trapped in ice was investigated as a new
pathway of iron supply. The dissolution experiments were carried out in the
absence and presence of various organic complexing ligands under dark
condition. In acidic pH conditions (pH 2, 3, and 4), the dissolution of iron
oxides was greatly enhanced in the ice phase compared to that in water. The
dissolved iron was mainly in the ferric form, which indicates that the
dissolution is not a reductive process. The extent of dissolved iron was
greatly affected by the kind of organic complexing ligands and the surface
area of iron oxides. The iron dissolution was most pronounced with high
surface area iron oxides and in the presence of strong iron binding ligands.
The enhanced dissolution of iron oxides in ice is mainly ascribed to the
"freeze concentration effect", which concentrates iron oxide particles,
organic ligands, and protons in the liquid like ice grain boundary region and
accelerates the dissolution of iron oxides. The ice-enhanced dissolution
effect gradually decreased when decreasing the freezing temperature from
−10 to −196 °C, which implies that the presence and formation of
the liquid-like ice grain boundary region play a critical role. The proposed
phenomenon of enhanced dissolution of iron oxides in ice may provide a new
pathway of bioavailable iron production. The frozen atmospheric ice with
iron-containing dust particles in the upper atmosphere thaws upon descending
and may provide bioavailable iron upon deposition onto the ocean surface.
Citation: Jeong, D., Kim, K., and Choi, W.: Accelerated dissolution of iron oxides in ice, Atmos. Chem. Phys., 12, 11125-11133, doi:10.5194/acp-12-11125-2012, 2012.