title: Vanillic and syringic acids from biomass burning: Behaviour during Fenton-like oxidation in atmospheric aqueous phase and in the absence of light.
abstract: Biomass combustion is a threat to the environment since it emits to the atmosphere organic compounds, which may react and originate others more aggressive. This work studied the behaviours of vanillic and syringic acids, small aromatic tracers of biomass burning, during Fenton-like oxidation in aqueous phase and absence of light. For both compounds, the extent of oxidation increased with pH decrease from neutral to acid in atmospheric waters, but for vanillic acid the neutral pH was not able of promoting the oxidation. With the oxidation of both acids were formed chromophoric compounds, and the formation rate increased with the degree of electron-donator substituents in benzene ring. The initial and produced compounds were not totally degraded up to 24h of reaction at pH 4.5, suggesting that the night period may be not sufficient for their full degradation in atmospheric waters. The major compounds formed were the 3,4-dihydroxybenzoic acid for vanillic acid, and the 1,4-dihydroxy-2,6-dimethoxybenzene for syringic acid. These findings suggest the occurrence of an ipso attack by the hydroxyl radical preferential to the methoxy and carboxyl groups of vanillic and syringic acids, respectively. It is important to highlight that for both aromatic acids the main compounds produced are also small aromatic compounds.
authors.affiliation: CESAM (Centre for Environmental and Marine Studies) & Department of Chemistry, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
authors.forename: Gabriela T A D
authors.initials: GT
authors.lastname: Santos
authors.affiliation: CESAM (Centre for Environmental and Marine Studies) & Department of Chemistry, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal. Electronic address: patricia.santos@ua.pt.
authors.forename: Patrícia S M
authors.initials: PS
authors.lastname: Santos
authors.affiliation: CESAM (Centre for Environmental and Marine Studies) & Department of Chemistry, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
authors.forename: Armando C
authors.initials: AC
authors.lastname: Duarte
mesh_terms: D018533:Biomass; D005707:Gallic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D062385:Hydroxybenzoates; D017745:Incineration; D010084:Oxidation-Reduction; D014641:Vanillic Acid / Q000737:chemistry*
chemical_list: D062385:Hydroxybenzoates; C009091:protocatechuic acid; D005707:Gallic Acid; C001945:syringic acid; D014641:Vanillic Acid
keywords: Aromatic acids; Atmospheric water; Biomass burning; Fenton-like reaction; Light absence