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Open AccessArticle

Enhanced Iron Solubility at Low pH in Global Aerosols

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School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332-0340, USA
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Environmental Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, USA
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Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, USA
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Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, FL 32306-4520, USA
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National High Magnetic Field Laboratory, 1800 E. Paul Dirac Drive, Tallahassee, FL 32310, USA
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School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332-0340, USA
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Institute of Chemical Engineering Sciences, Foundation for Research and Technology–Hellas, 70013 Patras, Greece
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National Observatory of Athens, Institute for Environmental Research and Sustainable Development, 15236 Penteli, Greece
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Department of Chemistry, University of Crete, 71003 Iraklion, Greece
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Department of Earth & Environmental Sciences, Rutgers University at Newark, Newark, NJ 07102, USA
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Amity Institute of Environmental Sciences, Amity University, Noida 201303, India
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Department of Environmental Science, Adigrat University, Adigrat P.O. Box: 50, Ethiopia
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Author to whom correspondence should be addressed.
Atmosphere 2018, 9(5), 201; https://doi.org/10.3390/atmos9050201
Received: 19 April 2018 / Revised: 16 May 2018 / Accepted: 20 May 2018 / Published: 22 May 2018
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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MDPI and ACS Style

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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