Organic aerosol concentration and composition over Europe: insights from comparison of regional model predictions with aerosol mass spectrometer factor analysis

Abstract

Abstract.A detailed three-dimensional regional chemical transport model (Particulate Matter Comprehensive Air Quality Model with Extensions, PMCAMx) was applied over Europe, focusing on the formation and chemical transformation of organic matter. Three periods representative of different seasons were simulated, corresponding to intensive field campaigns. An extensive set of AMS measurements was used to evaluate the model and, using factor-analysis results, gain more insight into the sources and transformations of organic aerosol (OA). Overall, the agreement between predictions and measurements for OA concentration is encouraging, with the model reproducing two-thirds of the data (daily average mass concentrations) within a factor of 2. Oxygenated OA (OOA) is predicted to contribute 93 % to total OA during May, 87 % during winter and 96 % during autumn, with the rest consisting of fresh primary OA (POA). Predicted OOA concentrations compare well with the observed OOA values for all periods, with an average fractional error of 0.53 and a bias equal to −0.07 (mean error = 0.9 µg m −3 , mean bias = −0.2 µg m −3 ). The model Published by Copernicus Publications on behalf of the European Geosciences Union. C. Fountoukis et al.: Organic aerosol concentration and composition over Europesystematically underpredicts fresh POA at most sites during late spring and autumn (mean bias up to −0.8 µg m −3 ). Based on results from a source apportionment algorithm running in parallel with PMCAMx, most of the POA originates from biomass burning (fires and residential wood combustion), and therefore biomass burning OA is most likely underestimated in the emission inventory. The sensitivity of POA predictions to the corresponding emissions' volatility distribution is discussed. The model performs well at all sites when the Positive Matrix Factorization (PMF)-estimated low-volatility OOA is compared against the OA with saturation concentrations of the OA surrogate species C * ≤ 0.1 µg m −3 and semivolatile OOA against the OA with C * > 0.1 µg m −3 .

ORACLE (v1.0): module to simulate the organic aerosol composition and evolution in the atmosphere

“…Several recent regional-scale modeling studies have accounted for the semivolatile nature and chemical aging of organic compounds demonstrating improvements in reproducing the organic aerosol budget and its chemical resolution (Murphy and Pandis, 2009;Tsimpidi et al, , 2011Hodzic et al, 2010;Fountoukis et al, 2011Fountoukis et al, , 2014Shrivastava et al, 2011;Bergström et al, 2012;Athanasopoulou et al, 2013;Zhang et al, 2013). However, such efforts on a global scale are limited.…”

Modeling the role of highly oxidized multifunctional organic molecules for the growth of new particles over the boreal forest region

“…In many studies (e.g., Bergström et al, 2012;Farina et al, 2010;Fountoukis et al, 2014;Hodzic et al, 2009;Lane et al, 2008;Murphy et al, 2012) the vapors are assumed to be semi-volatile and in equilibrium with the (liquid, well-mixed) particles, making it possible to model formation of BSOA by simple gas-particle equilibrium partitioning (Pankow, 1994). In other studies (e.g., Scott et al, 2015;Spracklen et al, 2008;Tunved et al, 2010;Westervelt et al, 2013) the vapors are assumed to be nonvolatile and the irreversible particle growth is only limited by the collision rate between the vapor molecules and the particles.…”

Heterogeneous chemistry and reaction dynamics of the atmospheric oxidants, O3, NO3, and OH, on organic surfaces

“…14,15 The concentrations of these types of organic aerosols typically range from 1 to 10 mg m À3 and can reach levels exceeding 15 mg m À3 in heavily industrialized environments. 16,17 Once formed, they nearly immediately begin contributing to the heterogeneous chemistry of the lower atmosphere. Surface reactions involving O 3 , NO 3 , and OH are known to alter the properties and fate of organic particulates, often in unexpected ways.…”