Polar organic compounds in rural PM2.5 aerosols from K-puszta, Hungary, during a 2003 summer field campaign: Sources and diel variations

[摘要] In the present study, we examined PM_2.5 continental rural backgroundaerosols, which were collected during a summer field campaign atK-puszta, Hungary (4 June-10 July 2003), a mixed coniferous/deciduousforest site characterized by intense solar radiation during summer. Emphasiswas placed on polar oxygenated organic compounds that provide information onaerosol sources and source processes. The major components detected atsignificant atmospheric concentrations were: (a) photo-oxidation products ofisoprene including the 2-methyltetrols (2-methylthreitol and2-methylerythritol) and 2-methylglyceric acid, (b) levoglucosan, amarker for biomass burning, (c) malic acid, an intermediate in the oxidationof unsaturated fatty acids, and (d) the sugar alcohols, arabitol andmannitol, markers for fungal spores. Diel patterns with highestconcentrations during day-time were observed for the 2-methyltetrols,which can be regarded as supporting evidence for their fast photochemicalformation from locally emitted isoprene. In addition, a diel pattern withhighest concentrations during day-time was observed for the fungal markers,suggesting that the release of fungal fragments that are associated with thePM_2.5 aerosol is enhanced during that time. Furthermore, a diel patternwas also found for levoglucosan with the highest concentrations at nightwhen wood burning may take place in the settlements around the samplingsite. In contrast, malic acid did not show day/night differences but wasfound to follow quite closely the particulate and organic carbon mass. Thisis interpreted as an indication that malic acid is formed in photochemicalreactions which have a much longer overall time-scale than that of isoprenephoto-oxidation, and the sources of its precursors are manifold, includingboth anthropogenic and natural emissions. On the basis of the highconcentrations found for the isoprene oxidation products during day-time, itcan be concluded that rapid photo-oxidation of isoprene is an importantatmospheric chemistry process that contributes to secondary organic aerosol(SOA) formation at K-puszta during summer.

[学科分类] 大气科学