ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-10-26607-2010 Iron dissolution kinetics of mineral dust at low pH during simulated atmospheric processing Shi Z. 1 Bonneville S. 1 Krom M. D. 1 Carslaw K. S. 2 Jickells T. D. 3 Baker A. R. 3 Benning L. G. 1 Earth and Biosphere Institute, School of Earth and Environment, University of Leeds, Leeds, UK Institute of Climate and Atmospheric Sciences, School of Earth and Environment, University of Leeds, Leeds, UK School of Environmental Sciences, University of East Anglia, Norwich, UK 08 11 2010 10 11 26607 26640 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-discuss.net/10/26607/2010/acpd-10-26607-2010.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/10/26607/2010/acpd-10-26607-2010.pdf

We investigated the iron (Fe) dissolution kinetics of African (Tibesti) and Asian (Beijing) dust samples at acidic pH with the aim of reproducing the low pH conditions in atmospheric aerosols. The Beijing dust and three size fractions of the Tibesti dust (<20 μm: PM<sub>20</sub>; <10 μm: PM<sub>10</sub>; and <2.5 μm: PM<sub>2.5</sub>) were dissolved at pH 1, 2 and/or 3 for up to 1000 h. In the first 10 min, all dust samples underwent an extremely fast Fe solubilisation. Subsequently, the Fe dissolution proceeded at a much slower rate before reaching a stable dissolution plateau. The time-dependant Fe dissolution datasets were best described by a model comprising three acid-extractable Fe pools each dissolving according to first-order kinetics. The dissolution rate constant <i>k</i> of each pool was independent of the source (Saharan or Asian) and the size (PM<sub>20</sub>, PM<sub>10</sub> or PM<sub>2.5</sub>) of the dust but highly dependent on pH. The "fast" Fe pool had a <i>k</i> (25 h<sup>−1</sup> at pH=1) of a similar magnitude to "dry" ferrihydrite nanoparticles and/or poorly crystalline Fe(III) oxyhydroxide, while the "intermediate" and "slow" Fe pools had $k$ values respectively 50–60 times and 3000–4000 times smaller than the "fast" pool. The "slow" Fe pool was likely to consist of both crystalline Fe oxide phases (i.e., goethite and/or hematite) and Fe contained in the clay minerals. The initial mass of the "fast", "intermediate" and "slow" Fe pools represented respectively about 0.5–2%, 1–3% and 15–40% of the total Fe in the dust samples. Furthermore, we showed that in systems with low dust/liquid ratios, Fe can be dissolved from all three phases, whereas at high dust/liquid ratios (e.g., in aerosols), sufficient Fe is solubilised from the "fast" phase to dominate the Fe dissolved and to suppress the dissolution of Fe from the other Fe pools. These data demonstrated that dust/liquid ratio and pH are fundamental parameters controlling Fe dissolution kinetics in the dust. In order to reduce errors in atmospheric and climate models, these fundamental controlling factors need to be included.

 References Baker, A. R., Weston, K., Kelly, S. D., Voss, M., Streu, P., and Cape J. N.: Dry and wet deposition of nutrients from the tropical Atlantic atmosphere: Links to primary productivity and nitrogen fixation, Deep-Sea Res. I, 54, 1704-1720, 2007. Baker, A. R. and Jickells, T. D.: Mineral particle size as a control on aerosol iron solubility, Geophys. Res. Lett., 33, L17608, doi:10.1029/2006GL026557, 2006. Bonneville, S, Behrends, T., Van Cappellen, P.: Solubility and dissimilatory reduction kinetics of iron(III) oxyhydroxides: A linear free energy relationship, Geochim. Cosmochim. Ac., 73, 5273–5282, 2009. Boudreau, B. P. and Ruddick, B. R.: On a reactive continuum representation of organic matter diagenesis, Am. J. Sci., 291, 507–538, 1991. Boyd, P., Jickells, T. D., Law, C. S., Blain, S., et al.: Mesoscale iron enrichment experiments 1993-2005: synthesis and future directions, Science, 315, 612–617, 2007. Boyd, P. W. and Ellwood, M. J.: The biogeochemical cycle of iron in the ocean, Nature Geosci., 3, 675-682, doi:10.1038/ngeo964, 2010. Cornell, R. M., Posner, A. M., and Quirk, J. P.: Kinetics and mechanisms of the acid dissolution of goethite (α-FeOOH), J. Inorg. Nucl. Chem., 38, 563–567, 1976. Cornell, R. M. and Schwertmann, U.: The Iron Oxides: Structure, Properties, Reactions, Occurrence and Uses, Wiley-VCH Publishers, New York, USA, 201–220; 345–364; 297–344, 2003. Cwiertny, D. M., Baltrusaitis, J., Hunter, G. J., Laskin, A. Scherer, M. M., Grassian, V. H.: Characterization and acid-mobilization study of iron-containing mineral dust source materials, J. Geophys. Res., 113, D05202, 2008. Desboeufs, K. V., Sofikitis, A., Losno, R. Colin, J. L., and Ausset, P.: Dissolution and solubility of trace metals from natural and anthropogenic aerosol particulate matter, Chemosphere, 58, 195–203, 2005. Fan, S.-M., Moxim, W. J., Levy II, H.: Aeolian input of bioavailable iron to the ocean, Geophys. Res. Lett., 33, L07602, 2006. Fu. H., Cwiertny, D. M., Carmichael, G. R., Scherer, M. M., and Grassian, V. H.: Photoreductive dissolution of Fe-containing mineral dust particles in acidic media, J. Geophy. Res., 115, D11304, doi:10.1029/2009JD012702, 2010. Hand, J. L., Mahowald, N. M., Chen, Y., Siefert, R. L., Luo, C., Subramaniam, A., and Fung, I.: Estimates of atmospheric-processed soluble iron from observations and a global mineral aerosol model: Biogeochemical implications, J. Geophys. Res., 109, D17205, doi:10.1029/2004JD004574, 2004. Hegg, D. A., Gao, S., and Jonsson, H.: Measurements of selected dicarboxylic acids in marine cloud water, Atmos. Res., 62, 1–10, 2002. Hsu, S. C., Wong, G. T. F., Gong, G. C., Shiah, F. K., Huang, Y. T., Kao, S. J., Tsai, F., Lung, S. C. C., Lin, F. J., and Lin, I. I.: Sources, solubility, and dry deposition of aerosol trace elements over the East China Sea, Marine Chem., 120, 116–127, 2010. Hyacinthe, C., Bonneville, S., and Van Cappellen, P.: Reactive Iron (III) in sediments: Chemical versus microbial extractions, Geochim. Cosmochim. Ac., 70, 4166–4180, 2006. Hyacinthe, C. and Van Cappellen, P.: An authigenic iron phosphate phase in estuarine sediments: composition, formation and chemical reactivity, Mar. Chem., 91, 227–251, 2004. Ito, A. and Feng, Y.: Role of dust alkalinity in acid mobilization of iron, Atmos. Chem. Phys., 10, 9237–9250, doi:10.5194/acp-10-9237-2010, 2010. Jickells, T. D., An, Z. S., Andersen, K. K., Baker, A. R., Bergametti, G., Brooks, N., Cao, J. J., Boyd, P. W., Duce, R. A., Hunter, K. A., Kawahata, H., Kubilay, N., LaRoche, J., Liss, P. S., Mahowald, N., Prospero, J. M., Ridgwell, A. J., Tegen, I., Torres, R.: Global iron connections between desert dust, ocean biogeochemistry, and climate, Science, 308, 67–71, 2005. Jones, T., Brown, P., BeruBe, K., Wlodarczyk, A., and Shao, L.: The physicochemistry and toxicology of CFA particles, J. Toxicol. Environ. Health A, 73(5), 341–354, 2010. 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, doi:10.1029/2007GL031589, 2008. Lafon, S., Sokolik, I. N., Rajot, J. L., Caquineau, S., and Gaudichet, A.: Characterization of iron oxides in mineral dust aerosols: Implications for light absorption, J. Geophys. Res., 111, D21207, doi:10.1029/2005JD007016, 2006. Larsen, O. and Postma, D.: Kinetics of reductive bulk dissolution of lepidocrocite, ferrihydrite, and goethite, Geochim. Cosmochim. Acta, 65, 1367–1379, 2001. Luo, C., Mahowald, N. M., Meskhidze, N., Chen, Y., Siefert, R. L., Baker, A. R., and Johansen, A. M.: Estimation of iron solubility from observations and a global aerosol model, J. Geophys. Res., 110, D23307, doi:10.1029/2005JD006059, 2005. Mackie, D. S., Boyd, P. W., Hunter, K. A., and McTainsh, G. H.: Simulating the cloud processing of iron in Australian dust: pH and dust concentration, Geophys. Res. Lett., 32, L06809, doi:10.1029/2004GL022122, 2005. Mahowald, N. M., 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. Manktelow, P. T., Carslaw, K. S., Mann, G. W., and Spracklen, D. V.: The impact of dust on sulfate aerosol, CN and CCN during an East Asian dust storm, Atmos. Chem. Phys., 10, 365–382, doi:10.5194/acp-10-365-2010, 2010. Martin, J. H., Coale, K. H., Johnson, K. S., et al.: Testing the iron hypothesis in ecosystems of the equatorial Pacific Ocean, Nature, 371, 123–129, 1994 Meskhidze, N., Chameides, W. L., and Nenes, A.: Dust and pollution: A recipe for enhanced ocean fertilization?, J. Geophys. Res., 110, D03301, doi:10.1029/2004JD005082, 2005. Meskhidze, N., Chameides, W. L., Nenes, A., and Chen, G.: Iron mobilization in mineral dust: Can anthropogenic SO2 emissions affect ocean productivity?, Geophys. Res. Lett., 30, 2085, doi:10.1029/2003GL018035, 2003. Moore, C. M., Mills M. M., Achterberg, E. P., Geider, R. J., LaRoche, J., Lucas, M. I., McDonagh, E. L., Pan, X., Poulton, A. J., Rijkenberg, M. J. A., Suggett, D. J., Ussher, S. J., and Woodward, E. M. S.: Large-scale distribution of Atlantic nitrogen fixation controlled by iron availability, Nat. Geosci., 2, 867–871, 2009. Keene, W. C., Pszenny, A. A. P., Maben, J. R., and Sander, R.: Variation of marine aerosol acidity with particle size, Geophy. Res. Lett., 29(7), 1101, doi:10.1029/2001GL013881, 2002. Ogata, H., Zhang, D., Yamada, M., and Tobo, Y.: Comparison of elemental composition of Asian dust particles at Amami and Amakusa during a dust event, J. Jpn. Soc. Atmos. Environ., accepted, 2010. Ozsoy, T. and Ornektekin, S.: Trace elements in urban and suburban rainfall, Mersin, Northeastern Mediterranean, Atmos. Res., 94, 203–219, 2009. Postma, D.: The reactivity of iron oxides in sediments: a kinetic approach, Geochim. Cosmochim. Ac. 57, 5027–5034, 1993. Prospero, J. M., Ginoux, P., Torres, O., Nicholson, S. E., and Gill, T. E.: Environmental characterization of global sources of atmospheric soil dust dandified identified with the NIMBUS 7 Total Ozone Mapping Spectrometer (TOMS) absorbing aerosol product, Rev. Geophys., 40(1), 1002, doi:10.1029/2000RG000095, 2002. Raiswell, R., Vu, H. P., Brinza, L., and Benning, L. G.: The determination of labile Fe in ferrihydrite by ascorbic acid extraction: methodology, dissolution kinetics and loss of solubility with age and de-watering, Chem. Geo., 278, 20–79, doi:10.1016/j.chemgeo.2010.09.002, 2010. Raiswell, R., Benning, L. G., Tranter, M., and Tulaczyk, S.: Bioavailable iron in the Southern Ocean: the significance of the iceberg conveyor belt, Geochem. Trans., 9(7), doi:10.1029/2000RG000095, doi:10.1.1186/1467-4866-9-7, 2008. Rubasinghege, G., Lentz, R. W., Scherer, M. M., and Grassian, V. H.: Simulated atmospheric processing of iron oxyhydroxide minerals at low pH: Roles of particle size and acid anion in iron dissolution, PNAS, 107, 6628–6633, 2010. Schepanski, K., Tegen, I., Laurent, B., Heinold, B., and Macke, A. L.: A new Saharan dust source activation frequency map derived from MSG-SEVIRI IR channels, Geophys. Res. Lett., 34, L18803, doi:10.1186/1467-4866-9-7, 2007. Schwertmann, U.: Solubility and dissolution of iron oxides, Plant Soil, 130, 1–25, 1991. Shao, L., Li, W., Xiao, Z., and Sun, Z.: The mineralogy and possible sources of spring dust particles over Beijing, Adv. Atmos. Sci., 25, 395–403, 2008. Shi, Z., Shao, L., Jones, T. P., and Lu, S.: Microscopy and mineralogy of airborne particles collected during severe dust storm episodes in Beijing, China, J. Geophys. Res., 110, D01303, doi:10.1029/2004JD005073, 2005. Shi, Z., Zhang, D., Hayashi, M., Ogata, H., Ji, H., and Fujiie, W.: Influences of sulfate and nitrate on the hygroscopic behaviour of coarse dust particles, Atmos. Environ., 42, 822–827, doi:10.1016/j.atmosenv.2007.10.037, 2008. Shi, Z., Krom, M. D., Bonneville. S., Baker, A. R., Jickells, T. D., and Benning, L. G.: Formation of iron nanoparticles and increase in iron reactivity in the mineral dust during simulated cloud processing, Environ. Sci. Technol., 43, 6592–6596, doi:10.1021/es901294g, 2009. Shi, Z., Krom, M. D., Bonneville, S., Baker, A. R., Bristow, C., Drake, N., Mann, G., Carslaw, K., McQuaid, J. B., Jickells, T., Benning, L. G.: Influence of chemical weathering and aging of iron oxides on the potential iron solubility of Saharan dust during simulated atmospheric processing, Global Biogeochem. Cy., under review, 2010. Siefert, R. L., Pehkonen, S. O., Erel, Y., Hoffmann, M. R.: Iron photochemistry of aqueous suspensions of ambient aerosol with added organic acids, Geochim. Cosmochim. Ac., 58, 3271–3279, 1994. Solmon, F., Chuang, P. Y. Meskhidze, N., Chen, Y.: Acidic processing of mineral dust iron by anthropogenic compounds over the north Pacific Ocean, J. Geophys. Res., 114, D02305, doi:10.1029/2008JD010417, 2005. Spokes, J. L., Jickells, T. D., Lim, B.: Solubilisation of aerosol trace metals by cloud processing: A laboratory study, Geochim. Cosmochim. Ac., 58, 3281–3287, 1994. Spokes, L. J. and Jickells, T. D.: Factors controlling the solubility of aerosol trace metals in the atmosphere and on mixing into seawater, Aqua. Geochem., 1, 355–374, 1996. Straub, D. J., Lee, T., and Collett Jr., J. L.: Chemical composition of marine stratocumulus clouds over the eastern Pacific Ocean, J. Geophys. Res., 112, D04307, doi:10.1029/2006JD007439, 2007. Stumm, W. and Furrer, G.: The dissolution of oxides and aluminium silicates: Examples of surface-coordination-controlled kinetics, in: Aquatic surface chemistry, Stumm, W., John Wiley & Sons, New York, USA, 197–219, 1987. Sullivan, R. C., Guazzotti, S. A., Sodeman, D. A., and Prather, K. A.: Direct observations of the atmospheric processing of Asian mineral dust, Atmos. Chem. Phys., 7, 1213–1236, doi:10.5194/acp-7-1213-2007, 2007. Uno, I., Eguchi, K., Yumimoto, K., Takemura, T., Shimizu, A., Uematsu, M., Liu, Z., Wang, Z., Hara, Y., and Sugimoto, N.: Asian dust transported one full circuit around the~globe, Nature Geosci., 2, 557–560, 2009. Viollier, E., Inglett, P. W., Hunter, K., Roychoudhury, A. N., and Van Cappellen, P.: The ferrozine method revisited: Fe(II)/Fe(III) determination in natural waters, Appl. Geochem., 15, 785–790, 2000. Wieland, E. and Stumm, W.: Dissolution kinetics of kaolinite in acidic aqueous solutions at 25°C, Geochim. Cosmochim. Ac., 56, 3339–3355, 1992. Zhu, X., Prospero, J. M., Millero, F. J. Savoie, D. L., and Brass, G. W.: The solubility of ferric ion in marine mineral aerosol solutions at ambient relative humidities, Mar. Chem., 38, 91–107, 1992.