Characterization of aerosol chemical composition by aerosol mass spectrometry in Central Europe: an overview

Abstract
Real-time measurements of non-refractory submicron aerosols (NR-PM1) were conducted within the greater Alpine region (Switzerland, Germany, Austria, France and Liechtenstein) during several week-long ?eld campaigns in 2002–2009. A large variety of sites was covered including urban backgrounds, motorways, rural, remote, and high-Alpine stations, and also mobile on-road measurements were performed. Inorganic and organic aerosol (OA) fractions were determined by means of aerosol mass spectrometry (AMS). The average mass concentration of NR-PM1 for the di?erent campaigns typically ranged between 10 and 30 µgm
Overall, the organic portion was most abundant, ranging from 36% to 81% of NR-PM1 Other main constituents comprised ammonium (5–15%), nitrate (8–36%), sulfate (3–26%), and chloride (0–5%).
These latter anions were, on average, fully neutralized by ammonium. The OA was further divided (based on factor analysis, FA) into its underlying components, such as oxygenated (mostly secondary) organic aerosol (OOA), hydrocarbon-like and freshly emitted organic aerosol (HOA), as well as primary OA from biomass burning (P-BBOA). OOA was ubiquitous, ranged between 36% and 94% of OA, and could be separated into a low-volatility and a semi-volatile fraction (LV-OOA and SV-OOA) for all summer campaigns at low sites.

Introduction
Atmospheric aerosols are currently a subject of high scienti?c and political interest, which is due to their important e?ects on climate, human health, ecosystems and agricultural yields, as well as visibility. Particulate matter (PM) in the air represents 24987a complex mixture of organic matter, inorganic salts, trace elements, mineral dust, elemental carbon and water suspended in the air. Detailed analyses of physicochemical properties and spatiotemporal variability are crucial to understand the mechanisms of aerosol toxicity and their role in climate change.
The identi?cation and quanti?cation of processes and sources that govern global and regional aerosol abundances are the indispensable basis for e?cient abatement strategies. In this paper the chemical composition of non-refractory PM1 (particulate matter with an aerodynamic diameter of 1 µm or less) is investigated for various sites in the greater Alpine region (Switzerland, Germany, Austria, France and Liechtenstein), representing one of the most important economic and leisure areas in Europe. The analyzed datasets comprise aerosol mass spectrometric measurements from a high-Alpine (Jungfraujoch) and a pre-Alpine background location (Hohenpeissenberg), an Alpine village (Roveredo), rural-agricultural (Payerne), rural-kerbside (Reiden, H¨arkingen) and rural-industrial (Massongex) sites, two urban background sites (Z¨urich and Grenoble) as well as on-road mobile measurements in the Alpine Rhine Valley.

Summer campaigns and winter campaigns were analyzed.
Factor analytical approaches were applied to organic aerosol mass spectra (FAAMS) in order to identify and quantify the main organic subfractions, such as OOA (oxygenated organic aerosol), HOA (hydrocarbon-like organic aerosol), and P-BBOA 20 (primary biomass burning organic aerosol). The used methods are based on positive matrix factorization (PMF, Paatero and Tapper, 1993, 1994) and the multilinear engine (ME; Paatero, 1999). Their application to AMS organic data data was described in detail earlier (Lanz et al., 2007, 2008; Ulbrich et al., 2009). Alfarra et al. (2007), Lanz et al. (2007, 2008), and Weimer et al. (2009) have already described the OA composition 25 and origin for three sampling locations (Roveredo, Z¨urich, and Rhine Valley, respectively). The presentation of results of in-depth PMF analyses for the other sites is in preparation, e.g. by Favez et al. (2009) for Grenoble or by Perron et al. (2009) for Massongex. The AMS campaign in Hohenpeissenberg (Germany) was detailed by Hock et al. (2008).
The Multiple Chamber Aerosol Chemical Aging Experiments, or MUCHACHAS campaign, was a project jointly funded by EUROCHAMP and the U.S. EPA

Aerosol mass spectrometry
Aerosol mass spectra were obtained using three types of aerosol mass spectrometers
10 (AMS, Aerodyne Research Inc.) at 2–15min resolution for the ?xed measurement locations and 1 min averages for the mobile campaigns in the Rhine Valley. A detailed description of the AMS instruments can be found in Canagaratna et al., and references therein. In principle, aerosols are introduced through a critical ori?ce, separated from gaseous species by a series of aerodynamic lenses, focused on a particle beam and directed onto a vaporizer. After vaporization (at about 600 15 C) and electron ionization at 70 eV, the chemical composition is determined by the analysis of the resulting mass spectrum measured by a quadrupole (Q-AMS) or a Time-of-Flight mass spectrometer
Acknowledgements.
Concerning the ?eld campaigns in Switzerland and in the Rhine Valley we acknowledge funding of the Swiss Federal O?ce for the Environment (FOEN), Liechtenstein, Land Vorarlberg (Austria), Ostluft, the Cantons Grisons, Valais, St. Gallen, Zurich, and Lucerne,as well as EUCAARI (Jungfraujoch campaign). We thank U. P¨oschl and C. Schauer (EC datafor MOHp), the MOHp sta? (NOx and CO), as well as the International Foundation High Altitude Research Stations Jungfraujoch and Gornergrat (HFSJG). The Grenoble campaign was part of the FORMES program, funded under the PRIMEQUAL2 grant no. 0001135. A. Bor ´eave
20 is gratefully acknowledged for her help in the ?eld and within data analysis. P. F. DeCarlo is grateful for postdoctoral research support from the US-NSF (IRFP #0701013). We further acknowledge funding by IMBALANCE http://www.cces.ethz.ch/projects/clench/imbalance.

Average AMS-aerosol concentrations are for 13 campaigns in Central Europe

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