Source apportionment of size and time resolved trace elements and organic aerosols from an urban courtyard site in Switzerland

A Richard,K Appel,M F D Gianini,M C Minguillón,A S H Prévôt,U Baltensperger,P F Decarlo,M F Heringa,U Flechsig,R Chirico,N Bukowiecki,C Mohr,M Furger,P Lienemann

doi:10.5194/acp-11-8945-2011

Abstract

Abstract. Time and size resolved data of trace elements were obtained from measurements with a rotating drum impactor (RDI) and subsequent X-ray fluorescence spectrometry. Trace elements can act as indicators for the identification of sources of particulate matter <10 μm (PM10) in ambient air. Receptor modeling was performed with positive matrix factorization (PMF) for trace element data from an urban background site in Zürich, Switzerland. Eight different sources were identified for the three examined size ranges (PM1−0.1, PM2.5−1 and PM10−2.5): secondary sulfate, wood combustion, fire works, road traffic, mineral dust, de-icing salt, industrial and local anthropogenic activities. The major component was secondary sulfate for the smallest size range; the road traffic factor was found in all three size ranges. This trace element analysis is complemented with data from an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (AMS), assessing the PM1 fraction of organic aerosols. A separate PMF analysis revealed three factors related to three of the sources found with the RDI: oxygenated organic aerosol (OOA, related to inorganic secondary sulfate), hydrocarbon-like organic aerosol (HOA, related to road traffic) and biomass burning organic aerosol (BBOA), explaining 60 %, 22 % and 17 % of total measured organics, respectively. Since different compounds are used for the source classification, a higher percentage of the ambient PM10 mass concentration can be apportioned to sources by the combination of both methods.

Highlights

Ambient particulate matter concentrations have routinely been monitored in Europe
This paper describes a five-week winter campaign at the urban background site at Zurich Kaserne, Switzerland with focus on source apportionment applied to quantitative trace element and organic aerosol data
The RDI data were binned into 24-h intervals by calculating the mean of 12 data points and all three RDI-stages were summed up for a comparison to PM10, while PM1 filter values were compared to PM1−0.1 RDI values

Summary

Introduction

Measurements are often limited to the mass concentrations of particulate matter with aerodynamic diameter less than 10 μm (PM10) without information on the elemental composition and the size distribution of the aerosol particles. For the evaluation of the influence of atmospheric aerosols on human health (e.g. the toxicity of a metal when inhaled) and the dispersion via atmospheric transport, knowledge about the composition and size distribution is required. Trace elements represent a minor fraction of the atmospheric aerosol (generally in the order of a few percent), but they can act as specific tracers for several emission sources. Trace metals are found in almost all atmospheric aerosol size fractions of PM10. The organic component of atmospheric aerosols plays an important role mainly concerning particles with an aerodynamic diameter of less than 1 μm: at European continental mid-latitudes, a fraction of 20–50 % of the total fine mode aerosol mass can be attributed to organic matter (Putaud et al, 2004), and about 70 % of the organic carbon mass (suburban summer) is found in fine mode particles (Jaffrezo et al, 2005; Jimenez et al, 2009; Lanz et al, 2010)

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Results

Conclusion