ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-12-745-2012 Characterization of iron speciation in urban and rural single particles using XANES spectroscopy and micro X-ray fluorescence measurements: investigating the relationship between speciation and fractional iron solubility Oakes M. 1 Weber R. J. 1 Lai B. 2 Russell A. 3 Ingall E. D. 1 School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332, USA Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA School of Civil & Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA 16 01 2012 12 2 745 756 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/12/745/2012/acp-12-745-2012.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/12/745/2012/acp-12-745-2012.pdf

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 fractional iron solubility (soluble iron/total iron). In this study, iron speciation was determined in single particles at urban and rural sites in Georgia USA using synchrotron-based techniques, such as X-ray Absorption Near-Edge Structure (XANES) spectroscopy and microscopic X-ray fluorescence measurements. Soluble and total iron content (soluble + insoluble iron) of these samples was measured using spectrophotometry and synchrotron-based techniques, respectively. These bulk measurements were combined with synchrotron-based measurements to investigate the relationship between iron speciation and fractional iron 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 (e.g. elemental molar ratios of single particles based on microscopic X-ray fluorescence measurements) indicate that a majority (74%) of iron-containing 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.

 References Auffan, M., Achouak, W., Rose, J., Roncato, M., Chaneac, C., Waite, D. T., Masion, A., Woicik, J. C., Wiesner, M. R., and Bottero, J.: Relation between redox state of iron-based nanoparticles and their cytotoxicity toward escherichia coli, Environ. Sci. Technol. 42, 6730–6735, 2008. Bajt, S., Sutton, S. R., and Delaney, J. S.: X-ray microprobe analysis of iron oxidation states in silicates and oxides using X-ray absorption near edge structure (xanes), Geochim. Cosmochim. Ac., 58, 5209-5214, 1994. Baker, A. R. and Croot, P. L.: Atmospheric and marine controls on aerosol iron solubility in seawater, Mar. Chem., 120, 4–13, 2010 Baker, A. R. and Jickells, T. D.: Mineral particle size as a control on aerosol iron solubility, Geophys. Res. Lett., 33, http://dx.doi.org/10.1029/2006GL026557doi:10.1029/2006GL026557, 2006. Butler, A. J., Andrew, M. S., and Russell, A. G.: Daily sampling of PM$_2.5$ in atlanta: Results of the first year of the assessment of spatial aerosol composition in Atlanta study, J. Geophys. Res.-Atmos., 108, D7, http://dx.doi.org/10.1029/2002JD002234doi:10.1029/2002JD002234, 2003. Chuang, P. Y., Duvall, R. M., Shafer, M. M., and Schauer, J. J.: The origins of water soluble particulate iron in Asian outflow, Geophys. Res. Lett., 32, L07813, doi:0.1029/2004GL021946, 2005. Cornell, R. M. and Schwertmann, U.: The iron oxides: Structure, properties, reactions, occurences and uses, Wiley-VCH Verlag GmbH& Co. KGaA, Weinheim, 2003. Costa, D. L. and Dreher, K. L.: Bioavailable transition metals in particulate matter mediate cardiopulmonary injury in healthy and compromised animal models, Environ. Health Persp., 105, 1053–1060, 1997. Cwiertny, D. M., Baltrusaitis, J., Hunter, G. J., Laskin, A., Scherer, M. M., and Grassian, V. H.: Characterization and acid-mobilization study of iron-containing mineral dust source materials, J. Geophys. Res., 113, D05202, http://dx.doi.org/10.1029/2007JD00932doi:10.1029/2007JD00932, 2008. Deer, W. A., Howie, R. A., and Zussman, J.: An introduction to the rock forming minerals.Longman Group Limited, London, UK, 1978. Furukawa, T. and Takahashi, Y.: Oxalate metal complexes in aerosol particles: implications for the hygroscopicity of oxalate-containing particles, Atmos. Chem. Phys., 11, 4289–4301, http://dx.doi.org/10.5194/acp-11-4289-2011doi:10.5194/acp-11-4289-2011, 2011. Hoffmann, P., Dedik, A. N., Ensling, J., Weinbruch, S., Weber, S., Sinner, T., Gutlich, P., and Ortner, H. M.: Speciation of iron in atmospheric aerosol samples, J. Aerosol Sci., 27, 325–327, 1996. Ingall, E. D., Brandes, J. A., Diaz, J. M., de Jonge, M. D., Paterson, D., McNulty, I., Elliot, W. C., and Northrup, P.: Phosphorus K-edge XANES spectroscopy of mineral standards, J. Synchrotron. Radiat., 18, 18, http://dx.doi.org/10.1107/S0909049510045322doi:10.1107/S0909049510045322, 2011. Johansen, A. M., Siefert, R., and Hoffmann, M. R.: Chemical composition of aerosols collected over the tropical north atlantic ocean, J. Geophys. Res.-Atmos., 105, 15277–15312, 2000. Journet, E., Desboeufs, K. V., Caquineau, S., and Colin, J. L.: Mineralogy as a critical factor of dust iron solubility, Geophys. Res. Lett., 35, L07805, http://dx.doi.org/10.1029/2007GL031589doi:10.1029/2007GL031589, 2008. Keenan, C. R., Goth-Goldstein, R., Lucas, D., and Sedlak, D. L.: Oxidative stress induced by zero-valent iron nanoparticles and Fe(II) in human bronchial epithelial cells, Environ. Sci. Technol., 43, 4555–4560, 2009. Kelly, F. J.: Oxidative stress: Its role in air pollution and adverse health effects, Occup. Environ. Med., 60, 612–616, 2003. Lam, P. J. and Bishop, J. K.: The continental margin is a key source of iron to the hnlc north pacific ocean, Geophys. Res. Lett., 35, L07608, http://dx.doi.org/10.1029/2998GL033294doi:10.1029/2998GL033294, 2008. Liu, W., Wang, Y. H., Russell, A., and Edgerton, E. S.: Atmospheric aerosol over two urban-rural pairs in the southeastern united states: Chemical composition and possible sources, Atmos. Environ., 39, 4453–4470, 2005. Mahowald, N., Baker, A. R., Bergametti, G., Brooks, N., Duce, R. A., Jickells, T. D., Kubilay, N., Prospero, J. M., and Tegen, I.: Atmospheric global dust cycle and iron inputs to the ocean, Global Biogeochem. Cy., 19, GB4025, doi:10.1029/2004GB002402, 2005. Majestic, B. J., Schauer J. J., and Shafer, M. M.: Development of wet chemical method for the speciation of iron in atmospheric aerosols, Environ. Sci. Technol., 40, 2346–2351, 2006. Majestic, B. J., Schauer, J. J., and Shafer, M. M.: Application of synchrotron radiation for measurement of iron red-ox speciation in atmospherically processed aerosols, Atmos. Chem. Phys., 7, 2475–2487, http://dx.doi.org/10.5194/acp-7-2475-2007doi:10.5194/acp-7-2475-2007, 2007. Marcus, M. A., Westphal, A. J. and Fakra, S. C.: Classification of Fe-bearing species from k-edge xanes data using two parameter correlation plots, J. Synchrotron. Radiat., 15, 463–468, 2008. Meskhidze, N., Chameides, W. L., and Nenes, A.: Iron mobilization in mideral dust: Can anthropogenic SO2 emissions affect ocean productivity?, Geophys. Res. Lett., 30, 21, http://dx.doi.org/10.1029/2003GL018035doi:10.1029/2003GL018035, 2003. Oakes, M., Rastogi, N., Majestic, B. J., Shafer, M., Schauer, J. J., Edgerton, E. S., and Weber, R. J.: Characterization of soluble iron in urban aerosols using near-real time data, J. Geophys. Res.-Atmos., 115, D15302, http://dx.doi.org/10.1029/2009JD012532doi:10.1029/2009JD012532, 2010. Paris, R., Desboeufs, K. V., and Journet, E.,: Variability of dust iron solubility in atmospheric waters: investigateion of the role of oxalate organic complexation, Atmos. Environ., 45, 6510–6517, 2011. Pehkonen, S. O., Siefert, R., Erel, Y., Webb, S., and Hoffmann, M. R.: Photoreduction of iron oxyhydroxides in the presence of important atmospheric organic compounds, Environ. Sci. Technol., 27, 2056–2062, 1993. Prietzel, J., Thieme, J., Eusterhues, K., and Eichert, D.: Iron speciation in soils and soil aggregates by synchrotron-based x-ray \mboxmicrospectroscopy (xanes, mu-xanes), Eur. J. Soil. Sci., 58, 1027–1041, 2007. Schroth, A. W., Crusius, J., Sholkovitz, E. R., and Bostick, B. C.: Iron solubility driven by speciation in dust sources to the ocean, Nat. Geosci., 2, 337–340, 2009. See, S. W., Wang, Y. H., and Balasubramanian, R.: Contrasting reactive oxygen species and transition metal concentrations in combustion aerosols, Environ. Res., 103, 317–324, 2007. Shafer, M. M., Perkins, D. A., Antkiewicz, D. S., Stone, E. A., Quiraishi, T. A., and Schauer, J. J.: Reactive oxygen species acitivity and chemical speciation of size-fractionated atmospheric particlate matter from lahore, pakistan: An important role for transition metals, J. Environ. Monitor., 12, 704–415, 2010. Shi, Z., Krom, M. D., and Bonneville, S.: Formation of iron nanoparticles and increase in iron reactivity in mineral dust during simulated cloud processing, Environ. Sci. Technol., 43, 6592–6596, 2009. Shi, Z., Bonneville, S., Krom, M. D., Carslaw, K. S., Jickells, T. D., Baker, A. R., and Benning, L. G.: Iron dissolution kinetics of mineral dust at low pH during simulated atmospheric processing, Atmos. Chem. Phys., 11, 995–1007, http://dx.doi.org/10.5194/acp-11-995-2011doi:10.5194/acp-11-995-2011, 2011a. Shi, Z. B., Woodhouse, M. T., Carslaw, K. S., Krom, M. D., Mann, G. W., Baker, A. R., Savov, I., Fones, G. R., Brooks, B., Drake, N., Jickells, T. D., and Benning, L. G.: Minor effect of physical size sorting on iron solubility of transported mineral dust, Atmos. Chem. Phys., 11, 8459–8469, http://dx.doi.org/10.5194/acp-11-8459-2011doi:10.5194/acp-11-8459-2011, 2011b. Smith, K. R. and Aust, A. E.: Mobilization of iron from urban particulates leads to generation of reactive oxygen species in vitro and induction of ferritin synthesis in human lung epithlial cells, Chem. Res. Toxicol., 10, 828–834, 1997. Stookey, L. L.: Ferrozine – a new spectrophotometric reagent for iron, Anal. Chem., 42, 779–781, 1970. Takahama, S., Gilardoni, S. and Russell, L. M:. Single-particle oxidation state and morphology of atmospheric iron, J. Geophys. Res.-Atmos., 113, D22202, http://dx.doi.org/10.1029/2009JD009810doi:10.1029/2009JD009810, 2008. Valavanidas, A., Fiotakis, K., and Viachogianni, T.: Airborne particulate matter and human health: Toxicological assessment and importance of size and composition of particle for oxidative damage and carcinogenic mechanisms, J. Environ. Sci. Heal. C, 26, 339–362, 2008. Vidrio, E., Jung, H., and Anastasio, C.: Generation of hydroxyl radicals from dissolved transition metals in surrogate lung fluid solutions, Atmos. Environ., 42, 4369–4379, 2008. Werner, M. L., Nico, P. S., Marcus, M. A., and Anastasio, C.: Use of micro-xanes to speciate chromium in airborne fine particles in the sacramento valley, Environ. Sci. Technol., 41, 4919–4924, 2007. Wilke, M., Farges, F., Petit, P., Brown Jr, G. E., and Martin, F.: Oxidation state and coordination of fe in minerals: An Fe k-xanes spectroscopic study, American Mineralogist., 86, 714–730, 2001. Zhang, Y., Schauer, J., Shafer, M. M., Hannigan, M. P., and Dutton, S. J.: Source apportionment of in vitro reactive oxygen species bioassay activity from atmospheric particulate matter, Environ. Sci. Technol., 42, 7502–7509, 2008. Zhuang, G., Yi, Z., Duce, R. A., and Brown, P. R.: Link between iron and sulphur cycles suggested by detection of fe(ii) in remote marine aerosols, Nature, 355, 537–539, 1992.