ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-10-10521-2010 Aqueous chemistry and its role in secondary organic aerosol (SOA) formation Lim Y. B. 1 Tan Y. 1 Perri M. J. 2 Seitzinger S. P. 3 Turpin B. J. 1 Department of Environmental Sciences, Rutgers University, New Brunswick, NJ, USA Department of Chemistry, Sonoma State University, Rohnert Park, CA, USA Institute of Marine and Coastal Sciences, Rutgers University, Rutgers/NOAA CMER Program, New Brunswick, NJ, USA 10 11 2010 10 21 10521 10539 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/10/10521/2010/acp-10-10521-2010.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/10/10521/2010/acp-10-10521-2010.pdf

There is a growing understanding that secondary organic aerosol (SOA) can form through reactions in atmospheric waters (i.e., clouds, fogs, and aerosol water). In clouds and wet aerosols, water-soluble organic products of gas-phase photochemistry dissolve into the aqueous phase where they can react further (e.g., with OH radicals) to form low volatility products that are largely retained in the particle phase. Organic acids, oligomers and other products form via radical and non-radical reactions, including hemiacetal formation during droplet evaporation, acid/base catalysis, and reaction of organics with other constituents (e.g., NH<sub>4</sub><sup>+</sup>). <br><br> This paper provides an overview of SOA formation through aqueous chemistry, including atmospheric evidence for this process and a review of radical and non-radical chemistry, using glyoxal as a model precursor. Previously unreported analyses and new kinetic modeling are reported herein to support the discussion of radical chemistry. Results suggest that reactions with OH radicals tend to be faster and form more SOA than non-radical reactions. In clouds these reactions yield organic acids, whereas in wet aerosols they yield large multifunctional humic-like substances formed via radical-radical reactions and their O/C ratios are near 1.

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