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Atmosphere 2018, 9(5), 201;

Enhanced Iron Solubility at Low pH in Global Aerosols

School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332-0340, USA
Environmental Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, USA
Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, USA
Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, FL 32306-4520, USA
National High Magnetic Field Laboratory, 1800 E. Paul Dirac Drive, Tallahassee, FL 32310, USA
School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332-0340, USA
Institute of Chemical Engineering Sciences, Foundation for Research and Technology–Hellas, 70013 Patras, Greece
National Observatory of Athens, Institute for Environmental Research and Sustainable Development, 15236 Penteli, Greece
Department of Chemistry, University of Crete, 71003 Iraklion, Greece
Department of Earth & Environmental Sciences, Rutgers University at Newark, Newark, NJ 07102, USA
Amity Institute of Environmental Sciences, Amity University, Noida 201303, India
Department of Environmental Science, Adigrat University, Adigrat P.O. Box: 50, Ethiopia
Author to whom correspondence should be addressed.
Received: 19 April 2018 / Revised: 16 May 2018 / Accepted: 20 May 2018 / Published: 22 May 2018
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The composition and oxidation state of aerosol iron were examined using synchrotron-based iron near-edge X-ray absorption spectroscopy. By combining synchrotron-based techniques with water leachate analysis, impacts of oxidation state and mineralogy on aerosol iron solubility were assessed for samples taken from multiple locations in the Southern and the Atlantic Oceans; and also from Noida (India), Bermuda, and the Eastern Mediterranean (Crete). These sampling locations capture iron-containing aerosols from different source regions with varying marine, mineral dust, and anthropogenic influences. Across all locations, pH had the dominating influence on aerosol iron solubility. When aerosol samples were approximately neutral pH, iron solubility was on average 3.4%; when samples were below pH 4, the iron solubility increased to 35%. This observed aerosol iron solubility profile is consistent with thermodynamic predictions for the solubility of Fe(III) oxides, the major iron containing phase in the aerosol samples. Source regions and transport paths were also important factors affecting iron solubility, as samples originating from or passing over populated regions tended to contain more soluble iron. Although the acidity appears to affect aerosol iron solubility globally, a direct relationship for all samples is confounded by factors such as anthropogenic influence, aerosol buffer capacity, mineralogy and physical processes. View Full-Text
Keywords: iron solubility; aerosol pH; aerosol chemistry; synchrotron; aerosol iron iron solubility; aerosol pH; aerosol chemistry; synchrotron; aerosol iron

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Ingall, E.D.; Feng, Y.; Longo, A.F.; Lai, B.; Shelley, R.U.; Landing, W.M.; Morton, P.L.; Nenes, A.; Mihalopoulos, N.; Violaki, K.; Gao, Y.; Sahai, S.; Castorina, E. Enhanced Iron Solubility at Low pH in Global Aerosols. Atmosphere 2018, 9, 201.

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