Partially oxidised organic components in urban aerosol using GCXGC-TOF/MS

[摘要] Partially oxidised organic compounds associated with PM2.5 aerosol collectedin London, England, have been analysed using direct thermal desorptioncoupled to comprehensive gas chromatography-time of flight mass spectrometry(GCXGC-TOF/MS). Over 10000 individual organic components were isolated fromaround 10µg of aerosol material in a single procedure and with nosample pre-treatment. Chemical functionalities observed using thisanalytical technique ranged from alkanes to poly-oxygenated species. Thechemical band structures commonly used in GCXGC for group typeidentifications overlap for this sample type, and have required massspectrometry as an additional level of instrument dimensionality. Aninvestigation of oxygenated volatile organic compounds (o-VOC) containedwithin urban aerosol has been performed and in a typical sample around 130o-VOCs were identified based on retention behaviour and spectral match. Inexcess of 100 other oxygenated species were also observed but lack of massspectral library or pure components prevents positive identification. Manyof the carbonyl species observed could be mechanistically linked to gasphase aromatic hydrocarbon oxidation and there is good agreement in terms ofspeciation between the urban samples analysed here and those degradationproducts observed in smog chamber experiments of aromatic oxidation. Thepresence of partially oxidised species such as linear chain aldehydes andketones and cyclic products such as furanones suggests that speciesgenerated early in the oxidative process may undergo gas toparticle partitioning despite their relatively high volatility.

[学科分类] 大气科学