ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-9-25085-2009 Optical, physical and chemical characteristics of Australian Desert dust aerosols: results from a field experiment Radhi M. 1 Box M. A. 1 Box G. P. 1 Mitchell R. M. 2 Cohen D. D. 3 Stelcer E. 3 Keywood M. D. 2 School of Physics, University of New South Wales, Sydney NSW 2052, Australia CSIRO Marine and Atmospheric Research, Centre for Australian Weather and Climate Research, a partnership between CSIRO and the Australian Bureau of Meteorology, Australia Australian Nuclear Science and Technology Organisation, Menai NSW 2234, Australia 25 11 2009 9 6 25085 25125 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/9/25085/2009/acpd-9-25085-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/9/25085/2009/acpd-9-25085-2009.pdf

Mineral dust is one of the major components of the world's aerosol mix, having a number of impacts within the Earth system. However, the climate forcing impact of mineral dust is currently poorly constrained, with even its sign uncertain. As Australian deserts are more reddish than those in the northern hemisphere, it is important to better understand the physical, chemical and optical properties of this important aerosol. We have investigated the properties of Australian desert dust at a site in SW Queensland, which is strongly influenced by both dust and biomass burning aerosol. Three years of ground-based monitoring of spectral optical thickness has provided a statistical picture of gross aerosol properties. In November 2006 we undertook a field campaign which collected 4 sets of size-resolved aerosol samples for laboratory analysis – both ion beam analysis and ion chromatography.<br> <br> The aerosol optical depth data showed a weak seasonal cycle with an annual mean of 0.06&plusmn;0.03. The Angstrom coefficient showed a stronger cycle, indicating the influence of the winter-spring burning season in Australia's north. Size distribution inversions showed a bimodal character, with the coarse mode assumed to be mineral dust, and the fine mode a mixture of biomass burning and marine biogenic material. Ion Beam Analysis was used to determine the elemental composition of all filter samples, although elemental ratios were considered the most reliable output. Scatter plots showed that Fe, Al and Ti were well correlated with Si, and Co reasonably well correlated, with the Fe/Si ratio higher than the crustal average, as expected. Scatter plots for Ca, Mn and K against Si showed clear evidence of a second population, which in some cases could be identified with a particular sample day or size fraction. Ion Chromatography was used to quantify water soluble ions for 2 of our sample sets, showing the importance of marine influences on both fine (biogenic) and coarse (sea salt) modes.

 References Arimoto, R., Duce, R. A., Savoie, D. L., Prospero, J. M., Talbot, R., Cullen. J. D., Tomza, U., Lewis, N. F., and Ray, B. J.: Relationships among aerosol constituents from Asia and the North Pacific during PEMWest A, J. Geophys. Res., 101, 2011–2023, 1996. Ayers, G. P., Ivey, J. P., and Goodman, H. S.: Sulfate and Methanesulfonate in the maritime aerosol at Cape Grim, Tasmania, J. Atmos. Chem., 4, 173–185, 1986. Bates, T. S., Cline, J. D., Gammon, R. H., and Kelly-Hansen, S. R.: Regional and seasonal variations in the flux of oceanic dimethylsulfide to the atmosphere, J. Geophys. Res., 92, 2930–2938, 1987. Charlson, R. J., Schwartz, S. E., Hales, J. M., Cess, R. D., Coakley, J. A., Hansen, J. E., and Hofmann, D. J.: Climate forcing by anthropogenic aerosols, Science, 255, 423–430, 1992. Cohen, D. D.: Applications of simultaneous IBA techniques to aerosol analysis, Nucl. Instrum. Meth. B, 79, 385–388, 1993. Cohen, D. D.: Characterisation of atmospheric fine particles using IBA techniques, Nucl. Instrum. Meth. B, 136, 14–22, 1998. Cohen, D. D., Graham, M. B., and Kondepudi, R.: Elemental analysis by PIXE and other IBA techniques and their application to source fingerprinting of atmospheric fine particle pollution, Nucl. Instrum. Meth. B, 109–110, 218–226, 1996. Cohen, D. D., Siegele, R., Ivo, O., and Stelcer, E.: Long-term accuracy and precision of PIXE and PIGE measurements for thin and thick sample analyses, Nucl. Instrum. Meth. B, 189, 81–85, 2002. Dasch, J. M. and Cadle, S. H.: The removal of nitrate acid to atmospheric particles during a wintertime field study, Atmos. Environ., 24A, 2557–2562, 1990. Dentener, F. J., Carmichael, G. R., Zhang, Y., Lelieveld, J., and Crutzen, P. J.: Role of mineral aerosol as a reactive surface in the global troposphere, J. Geophys. Res., 101, 22869–22889, 1996. Dubovik, O., Holben, B., Eck, T. F., Smirnov, A., Kaufman, Y. J., King, M. D., Tanré, D., and Slutsker, I.: Variability of absorption and optical properties of key aerosol types observed in worldwide locations, J. Atmos. Sci., 59, 590–608, 2002. Dubovik, O. and King, M. D.: A flexible inversion algorithm for retrieval of aerosol optical properties from Sun and sky radiance measurements, J. Geophys. Res., 105, 20673–20696, 2000. Fitzgerald, J. W.: Marine aerosols: A review, Atmos. Environ., 25, 533–545, 1991. Forster, P., Ramaswamy, V., Atraxo, P., Bernsten, T., Betts, R., Fahey, D., Haywood, J., Lean, J., Lowe, D., Myhre, G., Nganga, J., Prinn, R., Raga, G., Schulz, M., and Dorland, R. V.: Changes in Atmospheric Constituents and in Radiative Forcing, in: Climate Change 2007: The Physical Science Basis, Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by: Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K. B., Tignor, M., and Miller, H. L., Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 2007. Gao, Y., Arimoto, R., Duce, R. A., Chen, L. Q., Zhou, M. Y., and Gu, D. Y.: Atmospheric non-sea-salt sulfate, nitrate and methanesulfonate over the China Sea, J. Geophys. Res., 101(D7), 12601–12611, 1996. Gloudemans, A. M. S., Krol, M. C., Meirink, J. F., de Laat, A. T. J., van der Werf, G. R., Schrijver, H., van den Broek, M. M. P., and Aben, I.: Evidence for long-range transport of carbon monoxide in the Southern Hemisphere from Sciamachy observations, Geophys. Res. Lett., 33, L16807, 2006. Harrison, R. M. and Pio, C. A.: Size-differentiated composition of inorganic atmospheric aerosols of both marine and polluted continental origin, Atmos. Environ., 17, 1733–1783, 1983. Holben, B. N., Eck, T. F., Slutsker, I., Tanre, D., Buis, J. P., Setzer, A., Vermote, E., Reagan, J. A., Kaufman, Y. J., Nakajima, T., Lavenu, F., Jankowiak, I., and Smirnov, A.: AERONET – A federated instrument network and data archive for aerosol characterization, Remote Sens. Environ., 66, 1–16, 1998. Huebert, B. J., Howell, S., Laj, P., Johnson, J. E., Bates, T. S., Quinn, P. K., Yegorov, V., Clarke A. D., and Porter, J. N.: Observations of the atmospheric sulfur cycle on SAGA 3, J. Geophys. Res., 98, 16985–16995, 1993. Jacob, D. J.: Heterogeneous chemistry and tropospheric ozone, Atmos. Environ., 34, 2131–2159, 2000. John, W., Wall, S. M., Ondo, J. L., and Winklmayr, W.; Modes in the size distributions of atmospheric inorganic aerosol, Atmos. Environ., 24A, 2349–2359, 1990. Kadowaki, S.: Size distribution of atmospheric total aerosols, sulfate, ammonium and nitrate particulate in the Nagoya area, Atmos. Environ., 10, 39–43, 1976. Keywood M. D., Ayers G. P., Gras J. L., Gillett R. W., and Cohen D. D.: Relationships between size segregated mass concentration data and ultrafine particle number concentrations in urban areas, Atmos. Environ., 33, 2907–2913, 1999. Kubilay, N., Cokacar, T., and Oguz, T.: Optical properties of mineral dust outbreaks over the northeastern Mediterranean, J. Geophys. Res., 108(D21), 4666, doi:10.1029/2003JD003798, 2003. Kulshrestha, U. C., Saxena, A., Kumar, N., Kumari, K. M., and Srivastava, S. S.: Chemical composition and association of size-differentiated aerosols at a suburban site in a semi-arid tract of India, J. Atmos. Chem., 29, 109–118, 1998. 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. Leck, C. and Rodhe, H.: Emissions of marine biogenic sulfur to the atmosphere of northern Europe, J. Atmos. Chem., 12, 63–86, 1991. Lide, D. R.: CRC Handbook of Chemistry and Physics, 78$^th$ edition, CRC Press, Boca Raton, Fl., 1997. Mamane, Y. and Gottlieb, J.: Nitrate formation on sea-salt and mineral particles a single particle approach, Atmos. Environ., 26A, 1763–1769, 1992. Marple, V. A., Rubow, K. L., and Behm, S. M.: A Microorifice Uniform Deposit Impactor (MOUDI): Description, calibration and use, Aerosol Sci, Tech., 14, 434–446, 1991. Mitchell, R. M. and Forgan, B. W.: Aerosol Measurement in the Australian Outback: Intercomparison of Sun Photometers, J. Atmos. Oceanic Tech., 20, 54–66, 2003. Millero, F. J. and Sohn, M. L.: Chemical Oceanography, CRC Press, Boca Raton, Fla., 1992. Nishikawa, M., Kanamori, S., Kanamori, N., and Mizoguchi, T.: Kosa aerosol as eolian carrier of anthropogenic material, Sci. Total Environ., 107, 13–27, 1991. Pakkanen, T. A., Kerminen, V. M., Hillamo, R. E., Makinen, M., Makela, T., and Virkkula, A.: Distribution of nitrate over sea-salt and soil derived particles – implications from a field study, J. Atmos. Chem., 24, 189–205, 1996. Parmar, R. S., Satsangi, G. S., Kumari, M., Lakhani, A., Srivastava, S. S., and Prakash, S.: Study of size distribution of atmospheric aerosol at Agra, Atmos. Environ., 35, 693–702, 2001. Prospero, J. M. and Savoie, D. L.: Effect of continental sources of nitrate concentrations over the Pacific Ocean, Nature, 33, 687–689, 1989. Qin, Y. and Mitchell, R. M.: Characterisation of episodic aerosol types over the Australian continent, Atmos. Chem. Phys., 9, 1943–1956, 2009. Quinn, P. K., Covert, D. S., Bates, T. S., Kapustin, V. N., Ramsey-Bell, D. C., and McInnes, L. M.: Dimethylsulfide/cloud condensation nuclei/climate system: Relevant size-resolved measurements of the chemical and physical properties of atmospheric aerosol particles, J. Geophy. Res., 98, 10411–10427, 1993. Ramanathan, V., Crutzen, P. J., Kiehl, J. T., and Rosenfeld, D.: Aerosols, climate, and the hydrological cycle, Science, 294, 2119–2124, 2001. Rosen, J. M., Young, S. A., Laby, J., Kjome, N., and Gras, J.: Springtime aerosol layers in the free troposphere over Australia: Mildura Aerosol Tropospheric Experiment (MATE 98), J. Geophys. Res., 105, 17833–17842, 2000. Saltzman, E. S., Savoie, D. L., Zika, R. G., and Prospero, J. M.: Methanesulphonic acid in the marine atmosphere, J. Geophys. Res., 88, 10897–10902, 1983. Savoie, D. L. and Prospero, J. M.: Particle size distribution of nitrate and sulfate in the marine atmosphere, Geophys. Res. Lett., 9, 1207–1210, 1982. Savoie, D. L., Prospero, J. M., Arimoto, R., and Duce, R. A.: Non-seasalt sulfate and methanesulfonate at American Samoa, J. Geophys. Res., 99, 3587–3596, 1994. Savoie, D. L., Arimoto, R., Keene, W. C., Prospero, J. M., Duce, R. A., and Galloway, J. N.: Marine biogenic and anthropogenic contributions to non-sea-salt-sulfate in the marine boundary layer over the North Atlantic Ocean, J. Geophys. Res., 107(D18), 4356, doi:10.1029/2001JD000970, 2002. Sokolik, I. N. and Toon, O. B.: Direct radiative forcing by anthropogenic airborne mineral aerosols, Nature, 381, 681–683, 1996. Sokolik, I. N., Winker, D. M., Bergametti, G., Gillette, D. A., Carmichael, G., Kaufman, Y. J., Gomes, L., Schuetz, L., and Penner, J. E.: Introduction to special section: outstanding problems in quantifying the radiative impacts of mineral dust, J. Geophys. Res., 106, 18015–18027, 2001. Tanaka, T. Y. and Chiba, M.: A numerical study of the contributions of dust source regions to the global dust budget, Glob. Planet. Change, 52, 88–104 2006. Tegen, I., Lacis, A. A., and Fung, I.: The influence on climate forcing of mineral aerosols from disturbed soils, Nature, 380, 419–422, 1996. Wolf, G. T.: On the nature of nitrate in coarse continental aerosols, Atmos. Environ., 18, 977–981, 1984. Wall, S. M., John, W., and Ondo, J. L.: Measurement of aerosol size distributions for nitrate and major ionic species, Atmos. Environ., 22, 1649–1656, 1988. Zhuang, H., Chan, C. K., Fang, M., and Wexler, A. S.: Size distributions of particulate sulfate, nitrate, and ammonium at a coastal site in Hong Kong, Atmos. Environ., 33, 843–853, 1999.