Gas/Particle partitioning measurements of organic acids were carried out during the Southern Oxidant and Aerosol Study (SOAS, 2013) at the Centerville, AL Supersite in the Southeast US during summertime, in a region with strong isoprene and terpene emissions. A Chemical Ionization High Resolution Time-of-Flight Mass Spectrometer (HRToF-CIMS), with acetate (CH3COO<sup>-</sup>) as the reagent ion was used to selectively analyze acids. The gas/particle partitioning was measured in near-real time using a Filter Inlet for Gases and AEROsols (FIGAERO). We investigate both individual species and bulk organic acids. The partitioning measurements are compared with those of three other instruments that can also quantify gas/particle partitioning with high time resolution: another HRToF-CIMS using I<sup>- </sup>as the reagent ion to ionize acids and other highly oxidized compounds, a Semivolatile Thermal Desorption Aerosol GC/MS (SV-TAG) and a Thermal Desorption Proton Transfer Time-of-Flight Mass Spectrometer (TD-PTRMS). This allows for comparison of the directly measured partitioning to models of partitioning to organic and water phases in the aerosol. The partitioning measurements for three of the instruments are generally consistent, with results in the same range for most species and following similar temporal trends and diurnal cycles. The TD-PTRMS measures on average ½ the partitioning to the particle phase of the acetate CIMS. Both the measurements and the model of partitioning to the organic phase respond quickly to temperature, and the model agrees with the measured partitioning within the error of the measurement for multiple compounds.

Gas/particle partitioning of organic acids during the southern oxidant and aerosol study (SOAS): Measurements and modeling

249th National Meeting (2015)

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