Observation of 2-methyltetrols and related photo-oxidation products of isoprene in boreal forest aerosols from Hyytiälä, Finland

[摘要] Oxidation products of isoprene including 2-methyltetrols (2-methylthreitoland 2-methylerythritol), 2-methylglyceric acid and triol derivatives ofisoprene (2-methyl-1,3,4-trihydroxy-1-butene (cis and trans) and3-methyl-2,3,4-trihydroxy-1-butene) have been detected in boreal forestPM₁ aerosols collected at Hyytiälä, southern Finland, during a2004 summer period, at significant atmospheric concentrations (in total 51 ng m⁻³in summer versus 0.46 ng m⁻³ in fall). On the basis ofthese results, it can be concluded that photo-oxidation of isoprene is animportant atmospheric chemistry process that contributes to secondaryorganic aerosol formation during summer in this conifer forest ecosystem. Inaddition to isoprene oxidation products, malic acid, which can be regardedas an intermediate in the oxidation of unsaturated fatty acids, was alsodetected at high concentrations during the summer period (46 ng m⁻³ insummer versus 5.2 ng m⁻³ in fall), while levoglucosan, originating frombiomass burning, became relatively more important during the fall period(29 ng m⁻³ in fall versus 10 ng m⁻³ in summer). Pinic acid, a majorphoto-oxidation product of α-pinene in laboratory experiments, couldonly be detected at trace levels in the summer samples, suggesting thatfurther oxidation of pinic acid occurs and/or that different oxidationpathways are followed. We hypothesize that photo-oxidation of isoprene mayparticipate in the early stages of new particle formation, a phenomenonwhich has been well documented in the boreal forest environment.

[学科分类] 大气科学