ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-9-8283-2009 Observations of heterogeneous reactions between Asian pollution and mineral dust over the Eastern North Pacific during INTEX-B McNaughton C. S. 1 Clarke A. D. 1 Kapustin V. 1 Shinozuka Y. 1 9 Howell S. G. 1 Anderson B. E. 2 Winstead E. 2 Dibb J. 3 Scheuer E. 3 Cohen R. C. 4 Wooldridge P. 4 Perring A. 4 Huey L. G. 5 Kim S. 5 Jimenez J. L. 6 Dunlea E. J. 6 DeCarlo P. F. 6 10 Wennberg P. O. 7 Crounse J. D. 7 Weinheimer A. J. 8 Flocke F. 8 School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, 96822 HI, USA NASA Langley Research Center, Hampton, 23665 VA, USA University of New Hampshire, Durham, 03824 NH, USA University of California Berkeley, Berkeley, 94720 CA, USA Georgia Institute of Technology, Atlanta, 30332 GA, USA Cooperative Institute for Research in Environmental Sciences (CIRES) and University of Colorado, Boulder, 80309 CO, USA California Institute of Technology, Pasadena, 91125 CA, USA National Center for Atmospheric Research, Boulder, 80307 CO, USA now at: NASA Ames Research Center, Moffett Field, 94035 CA, USA now at: Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland 03 11 2009 9 21 8283 8308 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/9/8283/2009/acp-9-8283-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/9/8283/2009/acp-9-8283-2009.pdf

In-situ airborne measurements of trace gases, aerosol size distributions, chemistry and optical properties were conducted over Mexico and the Eastern North Pacific during MILAGRO and INTEX-B. Heterogeneous reactions between secondary aerosol precursor gases and mineral dust lead to sequestration of sulfur, nitrogen and chlorine in the supermicrometer particulate size range. <br><br> Simultaneous measurements of aerosol size distributions and weak-acid soluble calcium result in an estimate of 11 wt% of CaCO<sub>3</sub> for Asian dust. During transport across the North Pacific, ~5–30% of the CaCO<sub>3</sub> is converted to CaSO<sub>4</sub> or Ca(NO<sub>3</sub>)<sub>2</sub> with an additional ~4% consumed through reactions with HCl. The 1996 to 2008 record from the Mauna Loa Observatory confirm these findings, indicating that, on average, 19% of the CaCO<sub>3</sub> has reacted to form CaSO<sub>4</sub> and 7% has reacted to form Ca(NO<sub>3</sub>)<sub>2</sub> and ~2% has reacted with HCl. In the nitrogen-oxide rich boundary layer near Mexico City up to 30% of the CaCO<sub>3</sub> has reacted to form Ca(NO<sub>3</sub>)<sub>2</sub> while an additional 8% has reacted with HCl. <br><br> These heterogeneous reactions can result in a ~3% increase in dust solubility which has an insignificant effect on their optical properties compared to their variability in-situ. However, competition between supermicrometer dust and submicrometer primary aerosol for condensing secondary aerosol species led to a 25% smaller number median diameter for the accumulation mode aerosol. A 10–25% reduction of accumulation mode number median diameter results in a 30–70% reduction in submicrometer light scattering at relative humidities in the 80–95% range. At 80% RH submicrometer light scattering is only reduced ~3% due to a higher mass fraction of hydrophobic refractory components in the dust-affected accumulation mode aerosol. Thus reducing the geometric mean diameter of the submicrometer aerosol has a much larger effect on aerosol optical properties than changes to the hygroscopic:hydrophobic mass fractions of the accumulation mode aerosol. <br><br> In the presence of dust, nitric acid concentrations are reduced to <50% of total nitrate (nitric acid plus particulate nitrate). NO<sub>y</sub> as a fraction of total nitrogen (NO<sub>y</sub> plus particulate nitrate), is reduced from >85% to 60–80% in the presence of dust. These observations support previous model studies which predict irreversible sequestration of reactive nitrogen species through heterogeneous reactions with mineral dust during long-range transport.

 References Aiken, A. C., Salcedo, D., Cubison, M. J., Huffman, J. A., DeCarlo, P. F., Ulbrich, I. M., Docherty, K. S., Sueper, D., Kimmel, J. R., Worsnop, D. R., Trimborn, A., Northway, M., Stone, E. A., Schauer, J. J., Volkamer, R. M., Fortner, E., de Foy, B., Wang, J., Laskin, A., Shutthanandan, V., Zheng, J., Zhang, R., Gaffney, J., Marley, N. A., Paredes-Miranda, G., Arnott, W. P., Molina, L. T., Sosa, G., and Jimenez, J. L.: Mexico City aerosol analysis during MILAGRO using high resolution aerosol mass spectrometry at the urban supersite (T0) – Part 1: Fine particle composition and organic source a pportionment, Atmos. Chem. Phys., 9, 6633–6653, 2009. Alfaro, S. C., Gomes, L., Rajot, J. L., Lafon, S., Gaudichet, A., Chatenet, B., Maille, M., Cautenet, G., Lasserre, F., Cachier, H., and Zhang, X. Y.: Chemcial and optical characterizatino of aerosols measured in spring 2002 at the ACE-ASia supersite, Zhenbeitai, China, J. Geophys. Res., $108$ (D23), 8641, doi:10.1029/2002JD003214, 2003. Anderson, T., Masonis, S. J., Covert, D. S., Ahlquist, N. C., Howell, S., Clarke, A. D., and McNaughton, C. S.: Variability of aerosol optical properties derived from in-situ aircraft measurements during ACE-Asia, J. Geophys. Res., 108(D23), 8647, doi:10.1029JD003247, 2003. Anderson, T. L., Covert, D. S., Marshall, S. F., Laucks, M. L., Charlson, R. J., Waggoner, A. P., Ogren, J. A., Caldow, R., R. L. Holm, F. R. Quant, G. J. Sem, A. Wiedensohler, N. A. Ahlquist, and T. S. Bates, Performance characteristics of a high-sensitivity, three-wavelength, total scatter/backscatter nephelometer, J. Atmos. Ocean. Technol., $13$(5), 967–986, 1996. Anderson, T. L. and Ogren, J. A.: Determining aerosol radiative properties using a TSI 3563 integrating nephelometer, Aerosol Sci. Technol., 29, 57–69, 1998. Andreae, M. O. and Crutzen, P. J.: Atmospheric Aerosols: Biogeochemical Sources and Role in Atmospheric Chemistry, Science, 276(5315), 1052–1058, 1997. Archuleta, C. M., DeMott, P. J., and Kreidenweis, S. M.: Ice nucleation by surrogates for atmospheric mineral dust andmineral dust/sulfate particles at cirrus temperatures, Atmos. Chem. Phys., $5$, 2617–2634, 2005. Arimoto, R., Kim, Y. J., Quinn, P. K., Bates, T. S., Anderson, T. L., Gong, S., Uno, I., Chin, M., Huebert, B. J., Clarke, A. D., Shinozuka, Y., Weber, R. J., Anderson, J. R., Guazzotti, S. A., Sullivan, R. C., Sodeman, D. A., Prather, K. A., and Sokolik, I. N.: Characterization of Asian Dust during ACE-Asia, Global Planet. Change, 52(1–4), 23–53, 2006. Arimoto, R., Zhang, X. Y., Huebert, B. J., Kang, C. H., Savoie, D. L., Prospero, J. M., Sage, S. K., Schloesslin, C. A., Khaing, H. M., and Oh, S. N.: Chemical composition of atmospheric aerosols from Zhenbeitai, China and Gosan, South Korea, during ACE-Asia, J. Geophys. Res., 109, D19S04, doi:10.1029/2003JD004323, 2004. Baron, P. A. and Willeke, K.: Aerosol Measurement: Principles, techniques, and applications, second edition, John Wiley and Sons Inc., 2001. Bauer, S. E. and Koch, D.: Impact of heterogeneoussulfate formation at mineral dust surfaces on aerosol loads and radiative forcing in the Goddard Institute for Space Studies general circulation model, J. Geophys. Res., 110, D17202, doi:10.1029/2005JD005870, 2005. Bauer, S. E., Mishchenko, M. I., Lacis, A. A., Zhang, S., Perlwitz, J., and Metzger, A. M.: Do sulfate and nitrate coatings on minearl dust have important effects on radiative properties and climate modelling?, J. Geophys. Res., 112, D06307, doi:10.1029/2005JD006977, 2007. Bergin, M. H., Ogren, J. A., Schwartz, S. E., and McInnes, L. M.: Evaporation of ammonium nitrate aerosol in a heated nephelometer: Implications for field measurements, Environ. Sci. Technol., 31(10), 2878–2883, 1997. Bian, H. and C. S. Zender: Mineral dust and global tropospheric chemistry: Relative roles ofphotolysis and heterogeneous uptake, J. Geophys. Res., 108(D21), 4672, doi:10.1029/2002JD003143, 2003. Blomquist, B.W., B.J. Huebert, S.G. Howell, M.R. Litchy, C.H. Twohy, A. Schanot, D. Baumgardner, B. Lafleur, R. Seebauch, and M.L. Laucks, An evaluation of the community aerosol inlet for the NCAR C-130 research aircraft, J. Atmos. Ocean. Technol., $18$ (8), 1387–1397, 2001. Bond, T. C., Bussemer, M., Wehner, B., Keller, S., Charlson, R. J., and Heintzenberg, J.: Light absorption by primary particle emissions from a lignite burning plant, Environ. Sci. Technol., $33$(21), 3887–3891, 1999. Boucher, O. and Anderson, T. L.: General circulation model assessment of the sensitivity of direct climate forcing by anthropogenic sulfate aerosols to aerosol size and chemistry, J. Geophys. Res., $100$(D12), 26117–26134, 1995. Brock, C. A., Sullivan, A. P., Peltier, R. E., Weber, R. J., Wollny, A. G., Gouw, J. A. d., Middlebrook, A. M., Atlas, E. L., Stohl, A., Trainer, M. K., Cooper, O. R., Fehsenfeld, F. C., Frost, G. J., Holloway, J. S., Hubler, G., Neuman, J. A., Ryerson, T. B., Warneke, C., and Wilson, J. C.: Sources of particulate matter in the northeastern United States in summer: 2. Evolution of chemical and microphysical properties, J. Geophys. Res., $113$, D08302, doi:10.1029/2007JD009241, 2008. Canagaratna, M. R., Jayne, J. T., Jimenez, J. L., Allan, J. D., Alfarra, M. R., Zhang, Q., Onasch, T. B., Drewnick, F., Coe, H., Middlebrook, A., Delia, A. E., Williams, L. R., Trimborn, A., Northway, M. J., DeCarlo, P. F., Kolb, C. E., Davidovits, P., and Worsnop, D. R.: Chemical and Microphysical Characterization of Ambient Aerosols with the Aerodyne Aerosol Mass Spectrometer, Mass Spectrom. Rev., $26$, 185–222, 2007. Carrico, C. M., Kus, P., Rood, M. J., Quinn, P. K., and Bates, T. S.: Mixtures of pollution, dust, sea salt, and volcanic aerosol during ACE-Asia: Radiative properties as a function of relative humidity, J. Geophys. Res., $108$ (D23), ACE 18-1–ACE 18-18, 2003. 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(5043), 423–430, 1992. Chen, F. H., Shi, Q., and Wang, J. M.: Environmental changes documented by sedimentation of Lake Yiema in arid China since Late Glaciation, J. Paleolimnol., $22$, 159–169, 1999. Clarke, A. D.: A thermo-optic technique for in situ analysis of size-resolved aerosol physicochemistry, Atmos. Environ., $25A$, 635–644, 1991. Clarke, A. D., Collins, W. G., Rasch, P. J., Kapustin, V. N., Moore, K., Howell, S., and Fuelberg, H. E.: Dust and pollution transport on global scales: Aerosol measurements and model predictions, J. Geophys. Res., $106$(D23), 32555–32570, 2001. Clarke, A.D., C. McNaughton, V.N. Kapustin, Y. Shinozuka, S. Howell, J. Dibb, J. Zhou, B. Anderson, V. Brekhovskikh, H. Turner, and M. Pinkerton, Biomass burning and pollution aerosol over North America: Organic components and their influence on spectral optical properties and humidification response, J. Geophys. Res., $112$, D12S18, doi:10.1029/2006JD007777, 2007. Clarke, A. D., Shinozuka, Y., Kapustin, V. N., Howell, S., Huebert, B., Doherty, S., Anderson, T., Covert, D., Anderson, J., Hua, X., Moore, I. K. G., McNaughton, C., Carmichael, G., and Weber, R.: Size distributions and mixtures of dust and black carbon aerosol in Asian outflow: Physiochemistry and optical properties, J. Geophys. Res., $109$(D15), 1–20, 2004. Clarke, A.D., T. Uehara, and J.N. Porter, Atmospheric nuclei and related aerosol fields over the Atlantic: Clean subsiding air and continental pollution during ASTEX, J. Geophys. Res.-Atmos., $102$(D21), 25281–25292, 1997. Clarke, A. D., Varner, J. L., Eisele, F., Mauldin, R. L., Tanner, D., and Litchy, M.: Particle production in the remote marine atmosphere: Cloud outflow and subsidence during ACE 1, J. Geophys. Res.-Atmos., $103$(D13), 16397–16409, 1998. Cohen, D. D., Garton, D., Stelcer, E., Hawas, O., Want, T., Poon, S., Kim, J., Choi, B. C., Oh, S. N., Sin, H.-J., Ko, M. Y., and Uematsu, M.: Multielemental analysis and characterization of fine aerosols at several key ACE-Asia sites, J. Geophys. Res., $109$, D19S12, doi:10.1029/2003JD003569, 2004. Craig., R. F.: Soil Mechanics, E & FN Spon, New York, USA, 1997. Crounse, J. D., McKinney, K. A., Kwan, A. J., and Wennberg, P. O.: Measurement of gas-phase hydroperoxides by chemical ionization mass spectrometry (CIMS), Anal. Chem., $78$, 6726–6732, 2006. Dai, A., Fung, I., and Genio, A. D. D.: Surface observed global land precipitiation variations during 1900–1988, J. Climate, $10$, 2943–2962, 1997. Davis, D. D., Chen, G., Crawford, J. H., Liu, S., Tan, D., Sandholm, S. T., Jing, P., Cunnold, D. M., DiNunno, B., Browell, E. V., Grant, W. B., Fenn, M. A., Anderson, B. E., Barrick, J. D., Sachse, G. W., Vay, S. A., Hudgins, C. H., Avery, M. A., Lefer, B., Shetter, R. E., Heikes, B. G., Blake, D. R., Blake, N., Kondo, Y., and Oltmans, S.: An assessment of western North Pacific ozone photochemistry based on springtime observations from NASA's PEM&hyphen; West B (1994) and TRACE&hyphen;P (2001) field studies, J. Geophys. Res., $108$(D21), GTE 50-1–GTE 50-18, 2003. Day, D. A., Wooldridge, P. J., Dillon, M. B., Thornton, J. A., and Cohen, R. C.: A thermal dissociation laser-induced fluorescence instrument for in-situ detection of NO2, peroxy nitrates, alkyl nitrates, and HNO<sub>3</sub>, J. Geophys. Res., $107$(D6), doi:10.1029/2001JD000779, 2002. DeCarlo, P. F., Dunlea, E. J., Kimmel, R. E., Aiken, A. C., Sueper, D. T., Crounse, J. D., Wennberg, P. O., Emmons, L., Shinozuka, Y., Clarke, A. D., Zhou, J. C., Tomlinson, J. M., Collins, D., Knapp, D., Weinheimer, A., Campos, T., and Jimenez, J. L.: Fast airborne aerosol size and chemistry measurements above Mexico City and Central Mexico during the MILARGRO campaign, Atmos. Chem. Phys., $8$, 4027–4048, 2008. DeCarlo, P. F., Kimmel, R. E., Trimborn, A., Northway, M. J., Jayne, J. T., Aiken, A. C., Gonin, M., Fuhrer, K., Horvath, T., Docherty, K. S., Worsnop, D. R., and Jimenez, J. L.: Field-Deployable, High-Resolution, Time-of-Flight Aerosol Mass Spectrometer, Anal. Chem., $78$, 8281–8289, 2006. DeCarlo, P.F., J.G. Slowik, D.R. Worsnop, P. Davidovits, and J.L. Jimenez, Particle Morphology and Density Characterization by Combined Mobility and Aerodynamic Diameter Measurements. Part 1: Theory, Aerosol Sci. Technol., $38$, 1185–1205, 2004. Dentener, F., 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(D17), 22869–22889, 1996. Dentener, F., Kinne, S., Bond, T., Boucher, O., Cofala, J., Generoso, S., Ginoux, P., Gong, S., Hoelzemann, J. J., Ito, A., Marelli, L., Penner, J. E., Putaud, J. P., Textor, C., Schulz, M., van der Werf, G. R., and Wilson, J.: Emissions of primary aerosol and precursor gases in the years 2000 and 1750, prescribed data-sets for AeroCom, Atmos. Chem. Phys. Discuss., 6, 2703–2763, 2006. Derbyshire, E.: On the morphology, sediments, and origin of the Loess Plateau of centratl China, in: Mega-geomorphology, edited by: Gardner, R. and Scoging, H., Clarendon Press, Oxford, 172–194, 1983. Dibb, J. E., Talbot, R. W., Lefer, B. L., Scheuer, E., Gregory, G. L., Browell, E. V., Bradshaw, J. D., Sandholm, S. T., and Singh, H. B.: Distributions of beryllium-7 and lead-210 over the wesern Pacific: PEM West B, J. Geophys. Res., 102, 28287–28302, 1997. Dibb, J. E., Talbot, R. W., Scheuer, E., Seid, G., DeBell, L., Lefer, B., and Ridley, B.: Stratospheric influence on the northern North American free troposphere during TOPSE: 7 Be as a stratospheric tracer, J. Geophys. Res., $108$(D4), TOP~11-1–TOP~11-8, 2003a. Dibb, J. E., Talbot, R. W., Scheuer, E. M., Seid, G., Avery, M. A., and Singh, H. B.: Aerosol chemical composition in Asian continental outflow during the TRACE-P campaign: Comparison with PEM-West B, J. Geophys. Res., 108(D21), GTE 36-1–GTE 36-13, 2003b. Ding, Z. L., Sun, J. M., Yang, S. L., and Liu, T. S.: Geochemistry of the Pliocene red clay formation in the Chinese Loess Plateau and implications for its origin, source provenance and palioclimate change, Geochim. Cosmochim. Acta, $65$ (6), 901–913, 2001. Dunlea, E. J., DeCarlo, P. F., Aiken, A. C., Kimmel, J. R., Peltier, R. E., Weber, R. J., Tomlinson, J., Collins, D. R., Shinozuka, Y., McNaughton, C. S., Howell, S. G., Clarke, A. D., Emmons, L. K., Apel, E. C., Pfister, G. G., van Donkelaar, A., Martin, R. V., Millet, D. B., Heald, C. L., and Jimenez, J. L.: Evolution of Asian aerosols during transpacific transport in INTEX-B, Atmos. Chem. Phys., 9, 7257–7287, 2009. Eastwood, M. L., Cremel, S., Gehrke, C., Girard, E., and Bertram, A. K.: Ice nucleation on mineral dust particles: Onset conditions, nucleation rates and contact angles, J. Geophys. Res., $113$, D22203, doi:10.1029/2008JD010639, 2008. Eastwood, M. L., Cremel, S., Wheeler, M., Murray, B. J., Girard, E., and Bertram, A. K.: Effects of sulfuric acid and ammonium sulfate coatings on the ice nucleation properties of kaolinite particles, Geophys. Res. Lett., $36$, L02811, doi:10.1029/2008GL035997, 2009. Fan, S.-M., Horowitz, L. W., Levy II, H., and Moxim, W. J.: Impact of air pollution on wet deposition of mineral dust aerosols, Geophys. Res. Lett., $31$ L02104, doi:10.1029/2003GL018501, 2004. Fast, J. D., de Foy, B., Acevedo Rosas, A., Caetano, E., Carmichael, G., Emmons, L., McKenna, D., Mena, M., Skamarock, W. C., Tie, X., Coulter, R., Barnard, J. C., Wiedinmyer, C., and Madronich, S.; A meteorological overview of the MILAGRO field campaigns, Atmos. Chem. Phys., $7$, 2233–2257, 2007. Fuller, K.A., W.C. Malm, and S.M. Kreidenweis, Effects of mixing on extinction by carbonaceous particles, J. Geophys. Res., $104$(D13), 15941–15954, 1999. Ginoux, P., M. Chin, I. Tegen, J.M. Prospero, B. Holben, O. Dubovik, and S. Lin, Sources and distributions of dust aerosol simulated with the GOCART model, J. Geophys. Res., $106$ (D17), 20255–20273, 2001. Grassian, V. H.: Heterogeneous uptake and reaction of nitrogen oxides and volatile organic compounds on the surface of atmospheric particles including oxides, carbonates, soot and mineral dust: Implications for the chemical balance of the troposphere, Int. Rev. Phys. Chem., $20$(3), 467–548, 2001. Hand, J. L., and Kreidenweis, S. M.: A new method for retrieving particle refractive index and effective density from aerosol size distribution data, Aerosol Sci. Technol., $36$, 1012–1026, 2002. Harvey, M.: The iron CLAW, Environ. Chem., $4$, 396–399, 2007. Hess, M., Koepke, P., and Schult, I.: Optical properties of aerosols and clouds: The software package OPAC, B. Am. Meteor. Soc., $79$(5), 831–844, 1998. Howell, S. G., Clarke, A. D., Shinozuka, Y., Kapustin, V. N., McNaughton, C. S., Huebert, B. J., Doherty, S., and Anderson, T.: The Influence of relative humidity upon pollution and dust during ACE-Asia: size distributions and implications for optical properties, J. Geophys. Res., $111$, D06205, doi:10.1029/2004JD005759, 2006. Huebert, B. J., Howell, S. G., Covert, D. S., Bertram, T., Clarke, A. D., Anderson, J. R., Lafleur, B., Seebaugh, G. W. R., Wilson, J. C., Gesler, D., Blomquist, B. W., and Fox, J.: PELTI: Measuring the passing efficiency of an airborne low turbulence aerosol inlet, Aerosol Sci. Technol., $38$, 803–826, doi:10.1080/027868290500823, 2004. Huebert, B. J., Phillips, C. A., Zhuang, L., Kjellstrom, E., Rodhe, H., Feichter, J., and Land, C.: Long-term measurements of free-tropospheric sulfate at Mauna Loa: Comparison with global model simulations, J. Geophys. Res.-Atmos., $106$(D6), 5479–5492, 2001. Huffman, J. A., Ziemann, P. J., Jayne, J. T., Worsnop, D. R., and Jimenez, J. L.: Development and Characterization of a Fast-Stepping/Scanning Thermodenuder for Chemically-Resolved Aerosol Volatility Measurements, Aerosol Sci. Technol., $42$, 395–407, 2008. Husar, R. B., Tratt, D. M., Schichtel, B. A., Falke, S. R., Li, F., Jaffe, D., Gasso, S., Gill, T., Laulainen, N. S., Lu, F., Reheis, M. C., Chun, Y., Westphal, D. L., Holben, B. N., Gueymard, C., McKendry, I., Kuring, N., Feldman, G. C., McClain, C. R., Frouin, R., Merrill, C., Dubois, M., Vignola, F., Murayama, T., Nickovic, S., Wilson, W. E., Sassen, K., Sugimoto, N., and Malm, W. C.; Asian dust events of April 1998, J. Geophys. Res., $106$(D16), 18317–18330, 2001. Jacob, D. J.: Heterogeneous chemistry and tropospheric ozone, Atmos. Environ., $34$, 2131–2159, 2000. Jordan, C. E., Dibb, J. E., Anderson, B. E., and Fuelberg, H. E.: Uptake of nitrate and sulfate on dust aerosols during TRACE-P, J. Geophys. Res., $108$(D21), GTE 38-1–GTE 38-10, 2003a. Jordan, C. E., Dibb, J. E., and Finkel, R. C.: 10 Be/ 7 Be tracer of atmospheric transport and stratosphere-troposphere exchange, J. Geophys. Res., $108$(D8), ACL 3-1–ACL 3-14, 2003b. Karl, D. M., and Lukas, R. B.: The Hawaii Ocean Time-series (HOT) program: Background, rationale and field implementation, Deep-Sea Res. II, $43$, 129–156, 1996. Kelly, J. T., Chuang, C. C., and Wexler, A. S.: Influence of dust composition on cloud droplet formation, Atmos. Environ., $41$, 2904–2916, 2007. Kim, S., Huey, L. G., Stickel, R. E., Pierce, R. B., Chen, G., Avery, M. A., Dibb, J. E., Diskin, G. S., Sachse, G. W., McNaughton, C. S., Clarke, A. D., Anderson, B. E., and Blake, D. R.: Airborne measurements of HCl from the marine boundary layer to the lower stratosphere over the North Pacific Ocean during INTEX-B, Atmos. Chem. Phys. Discuss., $8$, 3563–3595, 2008. Kim, S., Huey, L. G., Stickel, R. E., Tanner, D. J., Crawford, J. H., Olson, J. R., Chen, G., Brune, W. H., Ren, X., Lesher, R., Wooldridge, P. J., Bertram, T. H., Perring, A. E., Cohen, R. C., Lefer, B., Shetter, R. E., Avery, M., Diskin, G., and Sokolik, I.: Measurement of pernitric acid in the free troposphere, J. Geophys. Res., $112$, D12S01, doi:10.1029/2006JD007676, 2007. Kinne, S., Schulz, M., Textor, C., Guibert, S., Balkanski, Y., Bauer, S. E., Berntsen, T., Berglen, T. F., Boucher, O., Chin, M., Collins, W., Dentener, F., Diehl, T., Easter, R., Feichter, J., Fillmore, D., Ghan, S., Ginoux, P., Gong, S., Grini, A., Hendricks, J., Herzog, M., Horowitz, L., Isaksen, I., Iversen, T., Kirkev&aring;g, A., Kloster, S., Koch, D., Kristjansson, J. E., Krol, M., Lauer, A., Lamarque, J. F., Lesins, G., Liu, X., Lohmann, U., Montanaro, V., Myhre, G., Penner, J., Pitari, G., Reddy, S., Seland, O., Stier, P., Takemura, T., and Tie, X.: An AeroCom initial assessment – optical properties in aerosol component modules of global models, Atmos. Chem. Phys., 6, 1815–1834, 2006. Kline, J., Huebert, B., Howell, S., Blomquist, B., Zhuang, J., Bertram, T., and Carrillo, J.: Aerosol composition and size versus altitude measured from the C-130 during ACE-Asia, J. Geophys. Res., $109$(D19), 1–22, 2004. Lafon, S., Sokolik, I., Rajot, J., 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. Lammel, G., and Novakov, T.: Water nucleation properties of carbon black and diesel soot particles, Atmos. Environ., $29$, 813–823, 1995. Liao, H., and Seinfeld, J. H.: Global impacts of gas-phase chemistry-aerosol interactions on direct radiative forcing by anthropogenic aerosol and ozone, J. Geophys. Res., $110$, D18208, doi:10.1029/2005JD005907, 2005. Liu, T.: Loess in China, China Ocean Press, Beijing, 1985. Maring, H., Savoie, D. L., Izaguirre, M. A., Custals, L., and Reid, J. S.: Mineral dust aerosol size distribution change during atmospheric transport, J. Geophys. Res., $108$(D19), PRD 8-1–PRD 8-6, 2003. Martin, J. H.: Glacial-interglacial CO<sub>2</sub> change: the iron hypothesis, Paleooceanography, $5$(1), 1–13, 1990. Martin, R. V., Jacob, D. J., Yantosca, R. M., Chin, M., and Ginoux, P.: Global and regional decreases in tropospheric oxidants from photochemical effects of aerosols, J. Geophys. Res., $108$(D3), 4097, 2003. Matsuki, A., Schwarzenboeck, A., Venzac, H., Laj, P., Crumeyrolle, S., and Gomes, L.: Effect of surface reaction on the cloud nucleating properties of mineral dust: AMMA aircraft campaign in summer 2006, Atmos. Chem. Phys. Discuss., $9$, 1797–1830, 2009. Mayol-Bracero, O. L., Gabriel, R., Andreae, M. O., Kirchstetter, T. W., Novakov, T., Ogren, J., Sheridan, P., and Streets, D. G.: Carbonaceous aerosols over the Indian Ocean during the Indian Ocean Experiment (INDOEX): Chemical characterization, optical properties, and probable sources, J. Geophys. Res., $107$(D19), INX2 29-1–INX2 29-21, 2002. McNaughton, C. S., Clarke, A. D., Howell, S. G., Pinkerton, M., Anderson, B., Thornhill, L., Hudgins, C., Winstead, E., Dibb, J. E., Scheuer, E., and Maring, H.: Results from the DC-8 Inlet Characterization Experiment (DICE): Airborne versus surface sampling of mineral dust and sea salt aerosols, Aerosol Sci. Technol., $41$(2), 136–159, 2007. Miyazaki, Y., Y. Kondo, N. Takegawa, R.J. Weber, M. Koike, K. Kita, M. Fukuda, Y. Ma, A.D. Clarke, V.N. Kapustin, F. Flocke, A.J. Weinheimer, M. Zondlo, F.L. Eisele, D.R. Blake, and B. Liley, Contribution of particulate nitrate to airborne measurements of total reactive nitrogen, J. Geophys. Res., $110$, D15304, doi:10.1029/2004JD005502, 2005. Moffet, R. C., de Foy, B., Molina, L. T., Molina, M. J., and Prather, K. A.: Measurement ofambient aerosol in northern Mexico City by single particle mass spectrometry, Atmos. Chem. Phys., $8$, 4499–4516, 2008. Molina, L. T., Madronich, S., Gaffney, J. S., and Singh, H. B.: Overview of MILAGRO/INTEX-B Campaign, IGACtivities Newsletter, 38, 2–15, 2008. Moulin, C., and I. Chiapello, Impact of human-induced desertification on the intensification of Sahel dust emission and export over the last decades, Geophys. Res. Lett., $33$, L18808, doi:10.1029/2006GL025923, 2006. Moya, M., Grutter, M., and Baez, A.: Diurnal variability of size-differentiated inorganic aerosol and their gas-phase precursors during January and February of 2003 near downtown Mexico City, Atmos. Environ., $38$, 5651–5661, 2004. Murphy, D. M., Cziczo, D. J., Froyd, K. D., Hudson, P. K., Matthew, B. M., Middlebrook, A. M., Peltier, R. E., Sullivan, A., Thomson, D. S., and Weber, R. J.: Single-particle mass spectrometry of tropospheric aerosol particles, J. Geophys. Res., $111$, D23S32, doi:10.1029/2006JD007340, 2006. Nicholson, S. E., Tucker, C. J., and Ba, M. B.: Desertification, drought, and surface vegetation: An example from the West African Sahel, B. Am. Meteor. Soc., $79$(5), 815–829, 1998. Osborne, S. R. and Haywood, J. M.: Aircraft observations of the microphysical and optical properties of major aerosol species, Atmos. Res., $73$, 173-201, 2005. Penner, J. E., Quaas, J., Storelvmo, T., Takemura, T., Boucher, O., Guo, H., Kirkev&aring;g, A., Kristjánsson, J. E., and Seland, \O.: Model intercomparison of indirect aerosol effects, Atmos. Chem. Phys., 6, 3391–3405, 2006. Petch, J. C.: Using a cloud-resolving model to study the effects of subgrid-scale variations in relative humidity on direct sulphate-aerosol forcing, Q. J. Roy. Meteor. Soc., $127$(577), 2385–2394, 2001. Phadnis, M.J., and G.R. Carmichael, Numerical investigation of the influence of mineral dust on the tropospheric chemistry of East Asia, J. Atmos. Chem., $36$ (3), 285–323, 2000. Porter, J. N., and Clarke, A. D.; Aerosol size distribution models based on in situ measurements, J. Geophys. Res.-Atmos., $102$(D5), 6035–6045, 1997. Prospero, J. M.: Long-range transport of mineral dust in the global atmosphere: Impact of African dust on the environment of the southeastern United States, Proc. Nat. Acad. Sci. USA, $96$, 3396–3403, 1999. Quinn, P. K., Bates, T. S., Baynard, T., Clarke, A. D., Onasch, T., Wang, W., Rood, M. J., Andrews, E., Allan, J., Carrico, C. M., Coffmann, D., and Worsnop, D.: Impact of particulate organic matter on the relative humidity dependence of light scattering: A simplified parameterization, Geophys. Res. Lett., $32$, L22809, doi:10.1029/2005GL024322, 2005. Reid, J. S., Jonsson, H. H., Maring, H. B., Smirnov, A., Savoie, D. L., Cliff, S. S., Reid, E. A., Livingston, J. M., Meier, M. M., Dubovik, O., and Tsay, S. C.: Comparison of size and morphological measurements of coarse mode dust particles from Africa, J. Geophys. Res., $108$(D19), PRD 9-1–PRD 9-28, 2003. Salcedo, D., Onasch, T. B., Dzepina, K., Canagaratna, M. R., Zhang, Q., Huffman, J. A., DeCarlo, P. F., Jayne, J. T., Mortimer, P., Worsnop, D. R., Kolb, C. E., Johnson, K. S., Zuberi, B., Marr, L. C., Volkamer, R., Molina, L. T., Molina, M. J., Cardenas, B., Bernabé, R. M., Márquez, C., Gaffney, J. S., Marley, N. A., Laskin, A., Shutthanandan, V., Xie, Y., Brune, W., Lesher, R., Shirley, T., and Jimenez, J. L.: Characterization of ambient aerosols in Mexico City during the MCMA-2003 campaign with Aerosol Mass Spectrometry: results from the CENICA Supersite, Atmos. Chem. Phys., 6, 925–946, 2006. Sassen, K.: Indirect climate forcing over the western US from Asian dust storms, Geophys. Res. Lett., $29$(10), 1465, 2002. Sassen, K., DeMott, P. J., Prospero, J. M., and Poellot, M. R.: Saharan dust storms and indirect aerosol effects on clouds: CRYSTAL-FACE results, Geophys. Res. Lett., $30$(12), 1633, 2003. Scheuer, E., Talbot, R. W., Dibb, J. E., Seid, G. K., DeBell, L., and Lefer, B.: Seasonal distributions of fine aerosol sulfate in the North American Arctic basin during TOPSE, J. Geophys. Res., $108$(D4), TOP 18-1–TOP 18-11, 2003. Schnaiter, M., Linke, C., Möhler, O., Naumann, K.-H., Saathoff, H., Wagner, R., Schurath, U., and Wehner, B.: Absorption amplification of black carbon internally mixed iwth secondary organic aerosol, J. Geophys. Res., $110$ D19204, doi:10.1029/2005JD006046, 2005. Seinfeld, J. H. and Pandis, S. N.: Atmospheric chemistry and physics: from air pollution to climate change, John Wiley and Sons, New York, USA, 1998. Sheehy, D.: A perspective on desertification of grazingland and ecosystems in North China, Ambio, $21$, 303–307, 1992. Singh, H. B., Brune, W. H., Crawford, J. H., Flocke, F., and Jacob, D. J.: Chemistry and transport of pollution over the Gulf of Mexico and the Pacific: spring 2006 INTEX-B campaign overview and first results, Atmos. Chem. Phys., 9, 2301–2318, 2009. Sjostedt, S., Huey, L. G., Tanner, D. J., Peischl, J., Chen, G., Dibb, J. E., Lefer, B., Hutterli, M. A., Beyersdorf, A. J., Blake, N. J., Blake, D. R., Sueper, D. T., Ryerson, T. B., Burkhar, J., and Stohl, A.: Observation of hydroxyl and the sum of peroxy radicals at Summit Greenland during summer 2003, Atmos. Environ., 41(24), 5122–5137, doi:10.1016/j.atmosenv.2006.06.065, 2007. Slowik, J. G., Stainken, K., Davidovits, P., Williams, L. R., Jayne, J. T., Kolb, C. E., Worsnop, D. R., Rudich, Y., DeCarlo, P. F., and Jimenez, J. L.: Particle morphology and density characterization by combined mobility and aerodynamic diameter measurements. Part 2: Application to combustion-generated soot aerosols as a function of fuel equivalence ratio, Aerosol Sci. Technol., $38$(12), 1206–1222, 2004. Slusher, D. L., Huey, L. G., Tanner, D. J., Flocke, F. M., and Roberts, J. M.: A thermal dissociation-chemical ionization mass spectrometer (TD-CIMS) technique for the simultaneous measurement of peroxyacul nitrates and dinitrogen pentoxide, J. Geophys. Res., $109$, D19315, doi:10.1029/2004JD004670, 2004. Sokolik, I. N. and Toon, O. B.: Direct radiative forcing by anthropogenic airborne mineral aerosols, Nature, $381$, 681–683, 1996. Sokolik, I. N., and Toon, O. B.: Incorporation of mineralogical composition into models of the radiative properties of mineral aerosol from UV to IR wavelengths, J. Geophys. Res., $104$(D8), 9423–9444, 1999. Solomon, F., Chuang, P. Y., Meskhidze, N., and 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, 2009. Song, C. H. and Carmichael, G. R.: Gas-particle partitioning of nitric acid modulated by alkaline aerosol, J. Atmos. Chem., $40$(1), 1–22, 2001. Stroud, C. A., Nenes, A., Jimenez, J. L., DeCarlo, P. F., Huffman, J. A., Bruintjes, R., Nemitz, E., Delia, A. E., Toohey, D. W., Guenther, A. B., and Nandi, S.: Cloud Activating Properties of Aerosol Observed during CELTIC, J. Atmos. Sci., $65$(2), 441–459, 2007. 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., $7$, 1213–1226, 2007a. Sullivan, R. C., Guazzotti, S. A., Sodeman, D. A., Tang, Y., Carmichael, G. R., and Prather, K. A.: Mineral dust is a sink for chlorine in the marine boundary layer, Atmos. Environ., $41$, 7166–7179, 2007b. Tang, I. N.: Thermodynamic and optical properties of mixed-salt aerosols of atmospheric importance, J. Geophys. Res., $102$(D2), 1883–1894, 1997. Tang, I. N. and Munkelwitz, H. R.: Water activities, densities, and refractive indices of aqueous sulfates and sodium nitrate droplets of atmospheric importance, J. Geophys. Res., $99$(D9), 18801–18808, 1994. Tang, I. N., Tridico, A. C., and Fung, K. H.: Thermodynamic and optical properties of sea salt aerosols, J. Geophys. Res., $102$(D19), 23269–23276, 1997. Tang, Y., Carmichael, G. R., Kurata, G., Uno, I., Weber, R., Song, C. H., Guttikunda, S. K., Woo, J. H., Streets, D. G., Wei, C., Clarke, A. D., Huebert, B., and Anderson, T. L.: Impacts of dust on regional tropospheric chemistry during the ACE-Asia experiment: A model study with observations, J. Geophys. Res., $109$, D19S21, doi:10.1029/2003JD003806), 2004. Tegen, I. and Fung, I.: Contribution to the atmospheric mineral aerosol load from land surface modification, J. Geophys. Res., $100$(D9), 18707–18726, 1995. Tegen, I. and Lacis, A. A.: Modeling of particle size distribution and its influence on the radiative properties of mineral dust aerosol, J. Geophys. Res., $101$(D14), 19237–19244, 1996. Tegen, I., Werner, M., Harrison, S. P., and Kohfeld, K. E.: Relative importance of climate and land use in determining present and future global soil dust emission, Geophys. Res. Lett., $31$, L05105, doi:10.1029/2003GL019216, 2004. Textor, C., Schulz, M., Guibert, S., Kinne, S., Balkanski, Y., Bauer, S., Berntsen, T., Berglen, T., Boucher, O., Chin, M., Dentener, F., Diehl, T., Easter, R., Feichter, H., Fillmore, D., Ghan, S., Ginoux, P., Gong, S., Grini, A., Hendricks, J., Horowitz, L., Huang, P., Isaksen, I., Iversen, I., Kloster, S., Koch, D., Kirkevåg, A., Kristjansson, J. E., Krol, M., Lauer, A., Lamarque, J. F., Liu, X., Montanaro, V., Myhre, G., Penner, J., Pitari, G., Reddy, S., Seland, Ø., Stier, P., Takemura, T., and Tie, X.: Analysis and quantification of the diversities of aerosol life cycles within AeroCom, Atmos. Chem. Phys., 6, 1777–1813, 2006. Thornton, J. A., Wooldridge, P. J., and Cohen, R. C.: Atmospheric NO<sub>2</sub>: In-situ laser-induced fluorescence detection at parts per trillion mixing ratios, Anal. Chem., $72$(3), 528–539, 2000. Twohy, C. H., Kreidenweis, S. M., Eidhammer, T., Browell, E. V., Heymsfield, A. J., Bansemer, A. R., Anderson, B. A., Chen, G., Ismail, S., DeMott, P. J., and Van Den Heever, S. C.: Saharan dust particles nucleate droplets in eastern Atlantic clouds, Geophys. Res. Lett., $36$, L01807, doi:10.1029/2008GL035846, 2009. Ullerstam, C. R., Vogt, R., Langer, S., and Ljungstrom, E.: The kinetics and mechanism of SO<sub>2</sub> oxidation by O<sub>3</sub> on mineral aerosol, Phys. Chem. Chem. Phys., $4$, 4694–4699, 2002. Underwood, G. M., Song, C. H., Phadnis, M., Carmichael, G. R., and Grassian, V. H.: Heterogeneous reactions of NO2 and HNO3 on oxides and mineral dust: A combined laboratory and modeling study, J. Geophys. Res.-Atmos., $106$(D16), 18055–18066, 2001. Usher, C. R., Al-Hosney, H., Carlos-Cuellar, S., and Grassian, V. H.: A laboratory study of the heterogeneous uptake and oxidation of sulfur dioxide on mineral dust particles, J. Geophys. Res., $107$(D23), 4713, doi:10.1029/2002JD002051, 2002. Virkkula, A., Ahlquist, N. C., Covert, D. S., Arnott, W. P., Sheridan, P. J., Quinn, P. K., and Coffman, D. J.: Modification, Calibration and a Field Test of an Instrument for Measuring Light Absorption by Particles, Aerosol Sci. Technol., $39$ 1, 68–83, doi:10.1080/027868290901963, 2005. Wang, Y. Q., Zhang, X. Y., Arimoto, R., Cao, J. J., and Shen, Z. X.: Characteristics of carbonate content and carbon and oxygen isotopic composition of northern China soil and ust aerosol and its application to tracing dust sources, Atmos. Environ., $39$, 2631–2642, 2005. Weinheimer, A. J., D. D. Montzka, T. L. Campos, et al.: Comparison between DC-8 and ER-2 species measurements in the tropical middle troposphere, J. Geophys. Res., $103$(D17), 22087–22096, 1998. Wyslouzil, B. E., Carleton, K. L., Sonnenfroh, D. M., Rawlins, W. T., and Arnold, S.: Observations of hydration of single, modified carbon aerosols, Geophys. Res. Lett., $21$, 2107–2110, 1994. Zimmermann, R., Weinbruch, S., Schutz, L., Hofmann, H., Ebert, M., Kandler, K., and Worringen, A.: Ice nucleation properties of the most abundant mineral dust phases, J. Geophys. Res., $113$, D23204, doi:10.1029/2008JD100655, 2008. Zondlo, M. A., Mauldin, R. L., Kosciuch, E., Cantrell, C. A., and Eisele, F. L.: Development and characterization of an airborne-based instrument used to measure nitric acid during the NASA Transport and Chemical Evolution over the Pacific field experiment, J. Geophys. Res.-Atmos., $108$(D20), 8793, doi:10.1029/2002JD003234, 2003.