Particle Size Distribution and Gas-Particle Partition of Polycyclic Aromatic Hydrocarbons in Helsinki Urban Area |
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| Authors: | Masahiko Shimmo Karri Saarnio Pasi Aalto Kari Hartonen Tuulia Hyötyläinen Markku Kulmala Marja-Liisa Riekkola |
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| Institution: | (1) Laboratory of Analytical Chemistry, Department of Chemistry, University of Helsinki, PO Box 55, FIN-00014, Finland;(2) Division of Atmospheric Sciences, Department of Physical Sciences, University of Helsinki, PO Box 64, FIN-00014, Finland |
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| Abstract: | Ambient concentrations of polycyclic aromatic hydrocarbons (PAHs) were measured in Helsinki (Finland). Particle mass size
distributions were obtained with a cascade impactor (12 stages) with glass fibre filters as substrates. Simultaneously with
the impactor measurements, particulate and gaseous PAHs were collected on a quartz filter and XAD-2 adsorbent, respectively,
for evaluation of gas-partition coefficients. Samples were analysed for PAHs by on-line coupled supercritical fluid extraction
— liquid chromatography — gas chromatography — mass spectrometry. The impactor results showed that most of the PAHs in Helsinki
urban area were concentrated in fine particles (<2.5 μm diameter) with unimode peak at about 1 μm. The results were comparable
with the number distribution measured with a differential mobility particle sizer. Total amounts of PAHs (gas + particle)
varied from 15 (acenaphthylene) to 1990 (fluorene) pg/m3. The PAHs lighter than 202 amu (pyrene and fluoranthene) were exclusively in gas phase, whereas those heavier than 202 amu
were mostly associated with particles. A plot of the partition coefficients (logKp) versus the temperature dependent sub-cooled
vapour pressures (logp
L
0
) showed a gradient of −0.66, which deviated from equilibrium state (gradient = −1). |
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| Keywords: | polycyclic aromatic hydrocarbons cascade impactor size distribution supercritical fluid extraction liquid chromatography — gas chromatography |
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