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

Abstract

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 which 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 (BBPOA) fractions contributed to a lesser extent (HOA from 3 to 30 %, and BBPOA from 1 to 39 %) with average contributions of 13 and 25 %, respectively. Modelled BBPOA fractions were 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 road transportation sector 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 werePublished by Copernicus Publications on behalf of the European Geosciences Union. 7654 G. Ciarelli et al.: Modelling winter organic aerosol at the European scale with CAMx also assessed: our results indicate that residential combustion gas-phase precursors in the semivolatile range (SVOC) contributed from 6 to 30 %, with higher contributions predicted at stations located in the southern part of the domain. On the other hand, the oxidation products of higher-volatility precursors (the sum of intermediate-volatility compounds (IVOCs) and volatile organic compounds (VOCs)) contribute from 15 to 38 % with no specific gradient among the stations.Although the new parameterization leads to a better agreement between model results and observations, it still underpredicts the SOA fraction, suggesting that uncertainties in the new scheme ...

Modeling organic aerosol concentrations and properties during winter 2014 in the northwestern Mediterranean region

“…In order to understand the behavior of the different parameterizations commonly used in CTMs to represent emissions and aging of I/S-VOCs in the western Mediterranean region, several simulations using different parameterizations, described in the following sections, are compared. These parameterizations are those described in Couvidat et al (2012), Koo et al (2014) and Ciarelli et al (2017b). The differences concern the emission ratios used to estimate I/S-VOCs from POAs (R and R RH ), the aging scheme (one step or multi-generational), the modeling of NTVOCs and the ratio OM : OC and volatility distribution at emissions.…”

“…Available measurements and modeling studies are useful in elucidating the composition and origin of OAs in different seasons Hayes et al, 2015;Canonaco et al, 2015;Chrit et al, 2017;Ciarelli et al, 2017b). Indeed, over the Mediterranean region, the oxidation of biogenic VOCs may dominate the formation of OAs during the summer (El Haddad et al, 2013;Minguillón et al, 2016;Chrit et al, 2017).…”

“…In winter, when anthropogenic emissions impact air quality the most, anthropogenic emissions such as toluene and xylene may also form SOAs, although they may be much less efficient than I/S-VOCs (Couvidat et al, 2013a;Sartelet et al, 2018). To take into account the emissions and aging of anthropogenic VOCs that are usually not considered in CTMs (phenol; naphthalene; m-,o-,p-cresol; etc., Ciarelli et al (2017b) p-benzenediol/2-methylfuraldehyde; dimethylphenols; guaiacol/methylbenzenediols; naphthalene; 2methylnaphthalene/1-methylnaphthalene; acenaphthylene; syringol; biphenyl/acenaphthene; and dimethylnaphthalene. Furthermore, they estimated the ratio NTVOC / SVOC, where SVOC is the primary semi-volatile organic matter, to be about 4.75.…”

“…Quantifying the effect of I/S-VOC emissions and their impact on the atmospheric organic budget as well as the OA oxidation and oxygenation levels during different seasons is challenging in spite of the recent advances concerning the description of I/S-VOCs (Stockwell et al, 2015;Ciarelli et al, 2017b). This work aims to evaluate how commonly used parameterizations and assumptions of I/S-VOCs emissions and aging perform to model the OA concentrations and properties in the western Mediterranean region in winter.…”

Reactive oxygen species (ROS) emissions and formation pathways in residential wood smoke under different combustion and aging conditions

“…The adverse health effects of PM are related to the aerosol chemical composition (Kelly and Fussell, 2012;Baltensperger et al, 2008). Residential wood combustion can contribute 5-44 % to the total ambient PM 2.5 (particulate matter with a diameter smaller than 2.5 μm), depending on the environment (Zhang et al, 2010;EPBE, 2005;USEPA, 2000;EEA, 2013a;Ciarelli et al, 2017). In addition to PM, wood combustion emits a wide range of gaseous pollutants, 45 including volatile organic compounds, which upon oxidation can form secondary organic aerosol.…”