XPS, SIMS and SNMS applied to a combined analysis of aerosol particles from a region of considerable air pollution in the upper Rhine valley

The water acceptance of aerosol particle surfaces is a key factor for atmospheric hygiene as it initiates gravitational settling by water up-take. To examine the concurrent influences on the surface of real airborne particles concerning the deposition of hydrophobic organic material, six particle sampling campaigns were performed in polluted outdoor-air under different air conditions. The particles were examined with SNMS, SIMS, and XPS with special view of the chemical inventory of the surface region. The total elemental inventory obtained with SNMS shows carbon compounds in all particle size classes. Soot seems to govern the submicron particles while the coarse fraction contains soil dust or fly ash. Depth-resolved analysis shows organic carbon compounds to be surface-enriched and to dominate the composition of the topmost molecular layers of the particles independent of the collection time and particle sizes. However, chlorides and ammonium sulfate were also found at the surface which will always reduce the hydrophobicity of the surface caused by organic compounds. No correlation was discovered between the ozone or NO2 concentration of the air and the type and quantity of the organic surface components.