Articles | Volume 18, issue 14
https://doi.org/10.5194/acp-18-10759-2018
https://doi.org/10.5194/acp-18-10759-2018
Research article
 | 
27 Jul 2018
Research article |  | 27 Jul 2018

Simulation of atmospheric organic aerosol using its volatility–oxygen-content distribution during the PEGASOS 2012 campaign

Eleni Karnezi, Benjamin N. Murphy, Laurent Poulain, Hartmut Herrmann, Alfred Wiedensohler, Florian Rubach, Astrid Kiendler-Scharr, Thomas F. Mentel, and Spyros N. Pandis

Abstract. A lot of effort has been made to understand and constrain the atmospheric aging of the organic aerosol (OA). Different parameterizations of the organic aerosol formation and evolution in the two-dimensional volatility basis set (2D-VBS) framework are evaluated using ground and airborne measurements collected in the 2012 Pan-European Gas AeroSOls-climate interaction Study (PEGASOS) field campaign in the Po Valley (Italy). A number of chemical aging schemes are examined, taking into account various functionalization and fragmentation pathways for biogenic and anthropogenic OA components. Model predictions and measurements, both at the ground and aloft, indicate a relatively oxidized OA with little average diurnal variation. Total OA concentration and O : C ratios are reproduced within experimental error by a number of chemical aging schemes. Anthropogenic secondary OA (SOA) is predicted to contribute 15–25 % of the total OA, while SOA from intermediate volatility compound oxidation contributes another 20–35 %. Biogenic SOA (bSOA) contributions varied from 15 to 45 % depending on the modeling scheme. Primary OA contributed around 5 % for all schemes and was comparable to the hydrocarbon-like OA (HOA) concentrations derived from the positive matrix factorization of the aerosol mass spectrometer (PMF-AMS) ground measurements. The average OA and O : C diurnal variation and their vertical profiles showed a surprisingly modest sensitivity to the assumed vaporization enthalpy for all aging schemes. This can be explained by the interplay between the partitioning of the semi-volatile compounds and their gas-phase chemical aging reactions.

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Short summary
Different parameterizations of the organic aerosol (OA) formation and evolution are evaluated using ground and airborne measurements collected in the 2012 PEGASOS field campaign in the Po Valley (Italy). Total OA concentration and O : C ratios were reproduced within experimental error by a number of schemes. Anthropogenic secondary OA (SOA) contributed 15–25 % of the total OA, 20–35 % of SOA from intermediate volatility compounds oxidation, and 15–45 % of biogenic SOA depending on the scheme.
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