ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-9-5155-2009 The formation, properties and impact of secondary organic aerosol: current and emerging issues Hallquist M. 1 Wenger J. C. 2 Baltensperger U. 3 Rudich Y. 4 Simpson D. 5 6 Claeys M. 7 Dommen J. 3 Donahue N. M. 8 George C. 9 10 Goldstein A. H. 11 Hamilton J. F. 12 Herrmann H. 13 Hoffmann T. 14 Iinuma Y. 13 Jang M. 15 Jenkin M. E. 16 Jimenez J. L. 17 Kiendler-Scharr A. 18 Maenhaut W. 19 McFiggans G. 20 Mentel Th. F. 18 Monod A. 21 Prévôt A. S. H. 3 Seinfeld J. H. 22 Surratt J. D. 23 Szmigielski R. 7 Wildt J. 18 Dept. of Chemistry, Atmospheric Science, University of Gothenburg, 412 96 Gothenburg, Sweden Dept. of Chemistry and Environmental Research Institute, University College Cork, Cork, Ireland Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland Dept. of Environmental Sciences, Weizmann Institute, Rehovot 76100, Israel EMEP MSC-W, Norwegian Meteorological Institute, P.B. 32 Blindern, 0313 Oslo, Norway Dept. of Radio and Space Science, Chalmers University of Technology, 41296, Gothenburg, Sweden Dept. of Pharmaceutical Sciences, University of Antwerp (Campus Drie Eiken), Universiteitsplein 1, 2610 Antwerp, Belgium Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh PA 15213, USA Université de Lyon, Faculté de Chimie, 69003, France CNRS, UMR5256, IRCELYON, Institut de recherches sur la catalyse et l'environnement de Lyon, Villeurbanne, 69626, France Dept. of Environmental Science, Policy and Management, University of California, Berkeley, CA, USA Dept. of Chemistry, University of York, Heslington, York, YO10 5DD, UK Leibniz-Institut für Troposphärenforschung, Permoserstrasse 15, 04318 Leipzig, Germany Johannes Gutenberg-Universität, Institut für Anorganische und Analytische Chemie, Duesbergweg 10–14, 55128 Mainz, Germany Dept. of Environmental Engineering Sciences, P.O. Box 116450, University of Florida, Gainesville, FL 32611-6450, USA Atmospheric Chemistry Services, Okehampton, Devon, EX20 1FB, UK Dept. of Chemistry & Biochemistry; and CIRES, University of Colorado, UCB 216, Boulder, CO 80309-0216, USA Institut für Chemie und Dynamik der Geosphäre, ICG, Forschungszentrum Jülich, 52425 Jülich, Germany Dept. of Analytical Chemistry, Institute for Nuclear Sciences, Ghent University, Proeftuinstraat 86, 9000 Ghent, Belgium Centre for Atmospheric Sciences, School of Earth, Atmospheric & Environmental Sciences, University of Manchester, Simon Building, Manchester, M13 9PL, UK Université Aix-Marseille I, II et III, Case 29, Laboratoire Chimie Provence, UMR-CNRS 6264, 3 place Victor Hugo, 13331 Marseille Cedex 3, France Depts. of Chemical Engineering and Environmental Science and Engineering, California Institute of Technology, Pasadena, CA 91125, USA Dept. of Chemistry, California Institute of Technology, Pasadena, CA 91125, USA 29 07 2009 9 14 5155 5236 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/9/5155/2009/acp-9-5155-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/9/5155/2009/acp-9-5155-2009.pdf

Secondary organic aerosol (SOA) accounts for a significant fraction of ambient tropospheric aerosol and a detailed knowledge of the formation, properties and transformation of SOA is therefore required to evaluate its impact on atmospheric processes, climate and human health. The chemical and physical processes associated with SOA formation are complex and varied, and, despite considerable progress in recent years, a quantitative and predictive understanding of SOA formation does not exist and therefore represents a major research challenge in atmospheric science. This review begins with an update on the current state of knowledge on the global SOA budget and is followed by an overview of the atmospheric degradation mechanisms for SOA precursors, gas-particle partitioning theory and the analytical techniques used to determine the chemical composition of SOA. A survey of recent laboratory, field and modeling studies is also presented. The following topical and emerging issues are highlighted and discussed in detail: molecular characterization of biogenic SOA constituents, condensed phase reactions and oligomerization, the interaction of atmospheric organic components with sulfuric acid, the chemical and photochemical processing of organics in the atmospheric aqueous phase, aerosol formation from real plant emissions, interaction of atmospheric organic components with water, thermodynamics and mixtures in atmospheric models. Finally, the major challenges ahead in laboratory, field and modeling studies of SOA are discussed and recommendations for future research directions are proposed.

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