Particle size-dependent concentrations of polycyclic aromatic hydrocarbons

Abstract

Particle size-dependent concentrations of PAHs from outdoor air sampling were measured. Size-segregated samples were collected at the outskirts of Munich in October 1994. A five-stage high-volume cascade impactor (HVS, particle diameter D_P < 10 µm, 810 l min^–1) and two Berner-type low-pressure cascade impactors (LPI, 79 l min^–1, six-stage, D_P= 0.04–21 µm and 29 l min^–1, nine-stage, D_P= 0.06–16 µm) were used. Eleven PAHs were quantified by HPLC with fluorescence detection. The concentrations of lead, bromine, zinc, sulfur and iron were measured by PIXE analysis. Particle number-concentrations in the range D_P= 0.01–1 µm were measured with a differential mobility analyser (DMA). The concentrations of the PAHs in particulate matter were in the range 0.8–3.8 ng m^–3. The concentrations found in the LPI samples always were higher than those in the samples taken with the HVS. The differences were in the range 30–63%. The results for the two LPI were in good agreement. The size-dependent PAH concentrations were similar with all three samplers. With the HVS, about 60% of the PAHs were found on the back-up filter (D_P < 0.66 µm). In the LPI samples 40% of the total PAHs were found on particles with D_P= 0.13–0.50 µm. Lead, bromine, zinc and sulfur showed the same distribution as the PAHs whereas iron had its maximum concentration at D_P= 2–4 µm. The measurements with the DMA gave unimodal distributions with the maximum in particle mass at D_P= 0.22–0.28 µm.