Homepage:
DAC Home

Chemical Characterisation of Pm2.5, Pm10 and Coarse Particles at Urban, near-City and Rural Sites in Switzerland

Hueglin, C., R. Gehrig, U. Baltensperger, M. Gysel, C. Monn and H. Vonmont
Atmospheric Environment, 2005, 39 (4), 637-651.

[W. Giger]

Daily PM2.5 and PM10 samples were taken from April 1998 to March 1999 at urban kerbside, urban background, near-city, and rural sites in Switzerland. The samples were analysed for mass, water soluble ions, trace elements, as well as elemental and organic carbon. The present paper focuses on the variation of element concentration between different site types and on the chemical mass closure of atmospheric particulate matter. Information on emission sources of trace elements is obtained by evaluation of the element abundances at sites that represent different pollution levels. The abundances of Ba, Ca, Ce, Cu, Fe, La, Mo, Mn, Pb, Sb, and Rh are gradually decreasing from urban kerbside to urban background, near-city and rural sites, indicating that road traffic is a main source of these elements. On the other hand, the abundances of Al, As, Cd, K, and V are similar for the different site types, which implies that emission sources are either spatially uniformly distributed (e.g. mineral dust), or there are no important regional emission sources and the ambient concentration of these elements might be dominated by long-range transport. When performing a mass closure, the annual average of the sum of aerosol chemical components was 22-27% for PM10 and 8-15% for PM2.5 lower than the PM mass. A drying procedure applied to a subset of PM10 samples and model calculations for PM2.5 samples according to their inorganic composition were used to estimate the contribution of retained water to the unaccounted mass at 50% RH. The obtained average water content was 10.6% for PM10 and 13-23% for PM2.5, clearly indicating that water is a major contributor to the unaccounted mass. Furthermore, a pronounced seasonal variation was observed with relatively lower water content in the colder season, indicating that the inorganic salts were mainly crystalline in winter, whereas they were probably dissolved during the rest of the year.
(C) 2004 Elsevier Ltd. All rights reserved.
[Hueglin, C., R. Gehrig, U. Baltensperger, M. Gysel, C. Monn and H. Vonmont]