with the exception of any material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work. details, including instrument design factors.Thanks are due to Robert Swinson for providing much of the new artwork, and to Scott Lowell for his keen-eyed proofreading. Two of us (M.A.T and M.T.) express our sincerest appreciation to our spouses and families for their patient endurance during the preparation of this book.

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Abstract.Carboxylic acids are present in substantial quantities in atmospheric particles, and they play an important role in the physical and chemical properties of aerosol particles. During measurements in coastal California in the summer of 2009, carboxylic acid functional groups were exclusively associated with a fossil fuel combustion factor derived from factor analysis of Fourier transform infrared spectroscopic measurements and closely correlated with oxygenated organic factors from aerosol mass spectrometry measurements. The high fraction of acid groups and the high ratio of oxygen to carbon in this factor suggest that this factor is composed of secondary organic aerosol (SOA) products of combustion emissions from the upwind industrial region (the ports of Los Angeles and Long Beach). Another indication of the photochemically-driven secondary formation of this combustion-emitted organic mass (OM) was the daytime increase in the concentrations of acid groups and the combustion factors. This daytime increase closely tracked the O 3 mixing ratio with a correlation coefficient of 0.7, indicating O 3 was closely associated with the SOA maximum and thus likely the oxidant that resulted in acid group formation. Using a pseudo-Lagrangian framework to interpret this daytime increase of carboxylic acid groups and the combustion factors, we estimate that the carboxylic acid groups formed in a 12-h daytime period of one day ("Today's SOA") accounted for 25-33 % of the measured carboxylic acid group mass, while the remaining 67-75 % (of the carboxylic acid group mass) was likely formed 1-3 days previously (the "Background SOA"). A similar estimate of the daytime increase in the combustion factors suggests that "Today's SOA" and the "Background SOA" respectively contributed 25-50 % and 50-75 % of the combustion factor (the "Total SOA"), for a "Total SOA" contribution to the OM of 60 % for the project Correspondence to: L. M. Russell (lmrussell@ucsd.edu) average. Further, size-resolved spectrometric and spectroscopic characterization of the particle OM indicate that the majority of the OM formed by condensation of gas-phase oxidation products. This unique set of measurements and methods to quantify and characterize photochemically and ozone-linked carboxylic acid group formation provide independent and consistent assessments of the secondary fraction of OM, which could result from second generation products of the oxidation of gas-phase alkane (molecules).