Heterogeneous reactions of ozone with methoxyphenols, in presence and absence of light Sopheak Net 1 , Elena Gómez Alvarez, Sasho Gligorovski * , Henri Wortham Université d’Aix-Marseille I, II, III-CNRS, UMR 6264, Laboratoire Chimie Provence, Equipe Instrumentation et Réactivité Atmosphérique, Case courrier 29, 3 place Victor Hugo, F 13331 Marseille Cedex 3, France article info Article history: Received 11 August 2010 Received in revised form 8 March 2011 Accepted 9 March 2011 Keywords: Heterogeneous reaction Photodegradation Methoxyphenols Silica particles Irradiation GC-MS abstract In this work, we investigated the heterogeneous reactions between gaseous ozone and seven particulate methoxyphenols, biomass tracers. The ozonolysis of silica particles coated with vanillin, vanillic acid, syringaldehyde, syringic acid, acetovanillone, acetonsyringone and coniferyl alcohol was studied successively and was carried out both in total darkness and under illumination with simulated solar light at 297 K. The condensed-phase products which emerged in such heterogeneous reactions were analyzed by gas chromatography-mass spectrometry (GC/MS). No reaction product was detected during the ozonolysis of vanillic acid, syringic acid, acetovanillone and acetosyringone under our experimental conditions. The main tranformation of pathway vanillin and syringaldehyde was the conversion of an aldehyde group to a carboxylic fonction. Thus, syringic acid and vanillic acid were respectively the main oxidation products of syringaldehyde and vanillin. The oxidation of coniferyl alcohol was relatively fast and the total degradation was observed after 16 h of ozone exposure. Five oxidation products: glycolic acid, oxalic acid, vanillin, vanillic acid and 3,4-dihydroxybenzoic acid, were identified and confirmed by their corresponding standards. It is inter- esting to note that 3,4-dihydroxybenzoic acid was detected only in the experiment performed under combined ozone and light exposure of the particles coated with coniferyl alcohol. Vanillin and vanillic acid also absorb light in the tropospheric actinic window and therefore they can be photochemically active which in turn can induce further modifications of the aerosol particles. A mechanistic pathway was proposed in order to elucidate the ozonolysis reaction of coniferyl alcohol and to explain the identified reaction products. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Biomass combustion is one of the major sources of fine organic materials (<2.5 mm), which can contribute an estimated more than 70% of the total organic fraction of aerosols and more than 50% of the mass PM2.5 in urban areas (Schauer and Cass, 2000; Jeong et al., 2008). European research programme CARBOSOL reported that biomass combustion (residential wood combustion, agricultural fire and fire of garden) contribute from 50 to 70% of carbon pollu- tion winter-time in Europe (Legrand and Puxbaum, 2007; Puxbaum et al., 2007; Gelencsér et al., 2007). Indeed, in the cities with more prevalent residential wood combustion such as in Northern Sweden, British Columbia (Canada) and in Christchurch (New Zealand), wood combustion has been estimated to account for as much as 70% (Hedberg and Johansson, 2006), 74% (Jeong et al., 2008) and 90% (McGovan et al., 2002) of PM2.5 winter-time respectively. Small-scale wood combustion has been associated with increased cardiac and respiratory hospital admission (Schreuder et al., 2006; Sarnat et al., 2008; Boman et al., 2003). Toxicological studies showed that wood combustion particles have caused inflammation and cytotoxicity (Karlsson et al., 2006; Kocbach et al., 2008a,b; Jalava et al., 2010). Natural wood is a complex and highly variable material con- sisting of three basic polymers: cellulose, lignin and hemicelluloses which are about 40e50%, 18e35% and 25e35% of the mass of dry wood respectively (Parham and Gray, 1984; Pettersen, 1984; Cheremisnoff, 1980). Methoxyphenols known as lignin pyrolysis products are major components in the wood smoke fine particles matter, and are also detected in the urban atmospheric samples * Corresponding author. Tel.: þ33 4 13 55 10 52; fax: þ33 4 13 5510 60. E-mail address: saso.gligorovski@univ-provence.fr (S. Gligorovski). 1 Current address: Université Lille 1-Sciences et Technologies, Laboratoire Géo- systèmes e FRE 3298, Equipe Chimie Analytique et Marine, Bât. C8 bureau 201, 59655 Villeneuve d’Ascq Cedex, France. Contents lists available at ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv 1352-2310/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2011.03.026 Atmospheric Environment 45 (2011) 3007e3014