Composition of extractable organic matter of air particles from rural and urban Portuguese areas

Atmospheric particulate matter (PM10) was collected simultaneously Lit thre e sites in the West Coast of Portugal, during an intensive campaign in Augu st 1996. The sites were located in line with the breezes blowing from the s ea. The collected aerosol was analysed in relation to black and organic car bon content. The particulate organic matter was extracted with solvents and characterised by gas chromatography and mass spectrometry (GC-MS). Most of the organic mass identified consists of alkanes. polycyclic aromatic hydro carbons (PAH), ketones, aldehydes, alcohols and fatty acids with both bioge nic and anthropogenic origin. Many photochemical products from volatile org anic compounds emitted by vegetation were also detected. Biomarkers such as 6,10,14-trimethylpentadecanone, abieta-8,11,13-trien-7-one and Patchouli a lcohol were observed at higher concentrations in the rural sites. Samples f rom the urban site present lower values of "carbon preference index" and hi gher concentrations of petrogenic/pyrogenic species, such as PAH. The PM10 concentrations and the total organic extract measured for the more interior site were generally lower, indicating that dispersion and dry deposition i nto the forest canopy were more important during the transport of the air m asses than aerosol production by condensation and photochemical reactions. On the contrary, The ratio between organic and black carbon was, in general , lower at sites near the coast, especially for compounds that evaporate at lower temperatures. The organic aerosol composition also seems to be stron gly dependent on the meteorology. (C) 2001 Elsevier Science Ltd. All rights reserved.