Atmos. Chem. Phys. Discuss., 10, 10399-10428, 2010
www.atmos-chem-phys-discuss.net/10/10399/2010/
doi:10.5194/acpd-10-10399-2010
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Role of dust alkalinity in acid mobilization of iron
A. Ito1 and Y. Feng2
1Research Institute for Global Change, JAMSTEC, Yokohama, Kanagawa, 236-0001, Japan
2Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0221, USA

Abstract. Atmospheric processing of mineral aerosols by acid gases (e.g., SO2, HNO3, N2O5, and HCl) may play a key role in the transformation of insoluble iron (Fe2O3) to soluble forms (e.g., Fe(II), inorganic soluble species of Fe(III), and organic complexes of iron). However, mineral dust particles also have a potential of neutralizing the acidic species due to the alkaline buffer ability of carbonate minerals (e.g., CaCO3 and MgCO3). Here we demonstrate the impact of dust alkalinity on the acid mobilization of iron in a three-dimensional aerosol chemistry transport model, which is incorporated with a mineral dissolution scheme. In our model simulations, most of the alkaline dust minerals cannot be entirely consumed by inorganic acids during the transport across the North Pacific Ocean. As a result, the inclusion of alkaline compounds in aqueous chemistry substantially limits the iron dissolution in aerosol solution during the long-range transport. Over the North Pacific Ocean, only a small fraction (<0.2%) of iron dissolves from hematite in the coarse-mode dust aerosols, when assuming internally mixed with carbonate minerals. However, if the iron-containing minerals are externally mixed with carbonate minerals, a significant amount (1–2%) of iron would dissolve from the acid mobilization. It implies that the alkaline content in dust aerosols might help to explain the inverse relationship between aerosol iron solubility and particle size.

Citation: Ito, A. and Feng, Y.: Role of dust alkalinity in acid mobilization of iron, Atmos. Chem. Phys. Discuss., 10, 10399-10428, doi:10.5194/acpd-10-10399-2010, 2010.
 
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