Atmos. Chem. Phys. Discuss., 11, 22771-22799, 2011
www.atmos-chem-phys-discuss.net/11/22771/2011/
doi:10.5194/acpd-11-22771-2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
Review Status
This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Characterization of iron speciation in single particles using XANES spectroscopy and micro X-ray fluorescence measurements: insight into factors controlling iron solubility
M. Oakes1, R. J. Weber1, B. Lai2, A. Russell3, and E. D. Ingall1
1School of Earth and Atmospheric Science, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
2Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
3School of Civil {&} Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA

Abstract. Soluble iron in fine atmospheric particles has been identified as a public health concern by participating in reactions that generate reactive oxygen species (ROS). The mineralogy and oxidation state (speciation) of iron have been shown to influence solubility. In this study, iron speciation was determined in single particles at urban and rural sites in Georgia USA using X-ray Absorption Near-Edge Structure (XANES) spectroscopy and microscopic X-ray fluorescence. Iron solubility of these samples was measured using spectrophotometry. These measurements (XANES and spectrophotometry) were combined to investigate the relationship between iron speciation and solubility in ambient aerosols. XANES measurements indicate that iron in the single particles was present as a mixture of Fe(II) and Fe(III), with Fe(II) content generally between 5 and 35 % (mean: ~25 %). XANES and elemental analyses indicate that a majority (74 %) of Fe particles are best characterized as Al-substituted Fe-oxides, with a Fe/Al molar ratio of 4.9. The next most abundant group of particles (12 %) was Fe-aluminosilicates, with Si/Al molar ratio of 1.4. No correlation was found between fractional iron solubility (soluble iron/total iron) and the abundance of Al-substituted Fe-oxides and Fe-aluminosilicates present in single particles at any of the sites during different seasons, suggesting solubility largely depended on factors other than differences in major iron phases.

Citation: Oakes, M., Weber, R. J., Lai, B., Russell, A., and Ingall, E. D.: Characterization of iron speciation in single particles using XANES spectroscopy and micro X-ray fluorescence measurements: insight into factors controlling iron solubility, Atmos. Chem. Phys. Discuss., 11, 22771-22799, doi:10.5194/acpd-11-22771-2011, 2011.
 
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