Precursors and formation of secondary organic aerosols from wildfires in the Euro-Mediterranean region

• Published in: Atmospheric chemistry and physics 2019-04, Vol.19 (8), p.5543-5569
• Main Authors: Majdi, Marwa, Sartelet, Karine, Lanzafame, Grazia Maria, Couvidat, Florian, Kim, Youngseob, Chrit, Mounir, Turquety, Solene
• Format: Article
• Language: English
• Subjects: Aerosols; Ageing; Aging; Air pollution; Air quality; Aromatic compounds; Benzene; Biomass burning; Burning; Catechin; Catechol; Chemical plants; Chemical properties; Computer simulation; Cresols; Emissions; Environmental aspects; Environmental Sciences; Fire plumes; Fires; Furans; Guaiacol; Hydrocarbons; Hydrophobicity; Measurement; Naphthalene; Nitrogen compounds; Organic chemistry; Organic compounds; Oxidation; Oxidation-reduction reactions; Oxides; Parameterization; Particulate matter; Phenols; Phenols (Class of compounds); Precursors; Secondary aerosols; Smog; Smog chambers; Summer; Thermal properties; Thermodynamic properties; Thermodynamics; Toluene; VOCs; Volatile organic compounds; Volatility; Wildfires; Xylene
• ISSN: 1680-7324; 1680-7316; 1680-7324
• DOI: 10.5194/acp-19-5543-2019

This work aims at quantifying the relative contribution of secondary organic aerosol (SOA) precursors emitted by wildfires to organic aerosol (OA) formation during summer of 2007 over the Euro-Mediterranean region, where intense wildfires occurred. A new SOA formation mechanism, H.sup.2 O.sub.aro, including recently identified aromatic volatile organic compounds (VOCs) emitted from wildfires, is developed based on smog chamber experiment measurements under low- and high-NO.sub.x regimes. The aromatic VOCs included in the mechanism are toluene, xylene, benzene, phenol, cresol, catechol, furan, naphthalene, methylnaphthalene, syringol, guaiacol, and structurally assigned and unassigned compounds with at least six carbon atoms per molecule (USC6). This mechanism H.sup.2 O.sub.aro is an extension of the H.sup.2 O (hydrophilic-hydrophobic organic) aerosol mechanism: the oxidation of the precursor forms surrogate species with specific thermodynamic properties (volatility, oxidation degree and affinity to water). The SOA concentrations over the Euro-Mediterranean region in summer of 2007 are simulated using the chemistry transport model (CTM) Polair3D of the air-quality platform Polyphemus, where the mechanism H.sup.2 O.sub.aro was implemented. To estimate the relative contribution of the aromatic VOCs, intermediate volatility, semi-volatile and low-volatility organic compounds (I/S/L-VOCs), to wildfires OA concentrations, different estimations of the gaseous I/S/L-VOC emissions (from primary organic aerosol - POA - using a factor of 1.5 or from non-methanic organic gas - NMOG - using a factor of 0.36) and their ageing (one-step oxidation vs. multi-generational oxidation) are also tested in the CTM.