ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-5-1805-2005 Polar organic compounds in rural PM<sub>2.5</sub> aerosols from K-puszta, Hungary, during a 2003 summer field campaign: Sources and diel variations Ion A. C. 1 Vermeylen R. 1 Kourtchev I. 1 Cafmeyer J. 2 Chi X. 2 Gelencsér A. 3 Maenhaut W. 2 Claeys M. 1 Department of Pharmaceutical Sciences, University of Antwerp (Campus Drie Eiken), Universiteitsplein 1, B-2610 Antwerp, Belgium Department of Analytical Chemistry, Inst. for Nuclear Sciences, Ghent University, Proeftuinstraat 86, B-9000 Gent, Belgium Air Chemistry Group of the Hungarian Academy of Sciences, University of Veszprém, Department of Earth and Environmental Sciences, Egyetem u. 10, H-8200 Veszprém, Hungary 22 07 2005 5 7 1805 1814 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/5/1805/2005/acp-5-1805-2005.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/5/1805/2005/acp-5-1805-2005.pdf

In the present study, we examined PM<sub>2.5</sub> continental rural background aerosols, which were collected during a summer field campaign at K-puszta, Hungary (4 June-10 July 2003), a mixed coniferous/deciduous forest site characterized by intense solar radiation during summer. Emphasis was placed on polar oxygenated organic compounds that provide information on aerosol sources and source processes. The major components detected at significant atmospheric concentrations were: (a) photo-oxidation products of isoprene including the 2-methyltetrols (2-methylthreitol and 2-methylerythritol) and 2-methylglyceric acid, (b) levoglucosan, a marker for biomass burning, (c) malic acid, an intermediate in the oxidation of unsaturated fatty acids, and (d) the sugar alcohols, arabitol and mannitol, markers for fungal spores. Diel patterns with highest concentrations during day-time were observed for the 2-methyltetrols, which can be regarded as supporting evidence for their fast photochemical formation from locally emitted isoprene. In addition, a diel pattern with highest concentrations during day-time was observed for the fungal markers, suggesting that the release of fungal fragments that are associated with the PM<sub>2.5</sub> aerosol is enhanced during that time. Furthermore, a diel pattern was also found for levoglucosan with the highest concentrations at night when wood burning may take place in the settlements around the sampling site. In contrast, malic acid did not show day/night differences but was found to follow quite closely the particulate and organic carbon mass. This is interpreted as an indication that malic acid is formed in photochemical reactions which have a much longer overall time-scale than that of isoprene photo-oxidation, and the sources of its precursors are manifold, including both anthropogenic and natural emissions. On the basis of the high concentrations found for the isoprene oxidation products during day-time, it can be concluded that rapid photo-oxidation of isoprene is an important atmospheric chemistry process that contributes to secondary organic aerosol (SOA) formation at K-puszta during summer.