| 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 field campaigns in 2002-2009. This region
represents one of the most important economic and recreational spaces in Europe.
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 different campaigns typically ranged between 10 and 30 μg
m-3. 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 variability in aerosol chemical composition in this region
could be largely explained when the measurement campaigns were sorted by time
of the year and position of the sites (Alpine valleys, elevated sites in the Alps, or
Plateau sites). 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 altitude sites.
Primary wood combustion (P-BBOA) accounted for a considerable fraction during
wintertime (17-49% OA), particularly in narrow Alpine valleys P-BBOA was often the
most abundant OA component. HOA/OA ratios were comparatively low for all
campaigns (6-16%) with the exception of on-road, mobile measurements (23%). |