Modelling winter organic aerosol at the European scale with CAMx: evaluation and source apportionment with a VBS parameterization based on novel wood burning smog chamber experiments
Giancarlo Ciarelli1, Sebnem Aksoyoglu1, Imad El Haddad1, Emily A. Bruns1, Monica Crippa2, Laurent Poulain3, Mikko Äijälä4, Samara Carbone5, Evelyn Freney6, Colin O'Dowd7, Urs Baltensperger1, and André S. H. Prévôt11Paul Scherrer Institute, Laboratory of Atmospheric Chemistry, 5232 Villigen PSI, Switzerland 2European Commission, Joint Research Centre (JRC ), Directorate for Energy, Transport and Climate, Air and Climate Unit, Via E. Fermi 274 9, I-21027 Ispra (VA), Italy 3Leibniz-Institute for Tropospheric Research (TR OPOS), Permoserstr. 15, 04318 Leipzig, Germany 4University of Helsinki, Department of Physics, Helsinki, Finland 5Institute of Physics, University of São Paulo, Rua do Matão Travessa R, 187, 05508-090 São Paulo, S.P., Brazil 6Laboratoire de Météorologie Physique (LaMP), CN RS/Université Blaise Pascal, Clermont-Ferrand, France 7School of Physics and Centre for Climate & Air Pollution Studies, Ryan Institute, National University of Ireland Galway, University R oad, Galway, Ireland
Received: 30 Aug 2016 – Accepted for review: 11 Oct 2016 – Discussion started: 21 Oct 2016
Abstract. We evaluated a modified VBS (Volatility Basis Set) scheme to treat biomass burning-like organic aerosol (BBOA) implemented in CAMx (Comprehensive Air Quality Model with extensions). The updated scheme was parameterized with novel wood combustion smog chamber experiments using a hybrid VBS framework that accounts for a mixture of wood burning organic aerosol precursors and their further functionalization and fragmentation in the atmosphere. The new scheme was evaluated for one of the winter EMEP intensive campaigns (February-March 2009) against aerosol mass spectrometer (AMS) measurements performed at 11 sites in Europe. We found a considerable improvement for the modelled organic aerosol (OA) mass compared to our previous model application with the mean fractional bias (MFB) reduced from −61 % to −29 %.
We performed model-based source apportionment studies and compared results against positive matrix factorization (PMF) analysis performed on OA AMS data. Both model and observations suggest that OA was mainly of secondary origin at almost all sites. Modelled secondary organic aerosol (SOA) contributions to total OA varied from 32 to 88 % (with an average contribution of 62 %) and absolute concentrations were generally under-predicted. Modelled primary hydrocarbon-like organic aerosol (HOA) and primary biomass burning-like aerosol (BBOA) fractions contributed to a lesser extent (HOA from 3 to 30 %, and BBOA from 1 to 39 %) with average contributions of 13 and 25 %, respectively. Modelled BBOA fractions was found to represent 12 to 64 % of the total residential heating related OA, with increasing contributions at stations located in the northern part of the domain.
Source apportionment studies were performed to assess the contribution of residential and non-residential combustion precursors to the total SOA. Non-residential combustion and transportation precursors contributed about 30–40 % to SOA formation (with increasing contributions at urban and near industrialized sites) whereas residential combustion (mainly related to wood burning) contributed to a larger extent, around 60–70 %. Contributions to OA from residential combustion precursors in different volatility ranges were also assessed: our results indicate that residential combustion gas-phase precursors in the semi-volatile range contributed from 6 to 30 %, with higher contributions predicted at stations located in the southern part of the domain. On the other hand, higher volatility residential combustion precursors contributed from 15 to 38 % with no specific gradient among the stations.
The new retrieved parameterization, although leading to a better agreement between model and observations, still under-predicts the SOA fraction suggesting remaining uncertainties in the new scheme or that other sources and/or formation mechanisms need to be elucidated.
Ciarelli, G., Aksoyoglu, S., El Haddad, I., Bruns, E. A., Crippa, M., Poulain, L., Äijälä, M., Carbone, S., Freney, E., O'Dowd, C., Baltensperger, U., and Prévôt, A. S. H.: Modelling winter organic aerosol at the European scale with CAMx: evaluation and source apportionment with a VBS parameterization based on novel wood burning smog chamber experiments
og, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-785, in review, 2016.