During the first Cloud and Aerosol Characterization Experiment (CLACE-1) in February and March 2000 various methods were used to characterize the aerosol at the high-alpine site Jungfraujoch, Switzerland (3580 m asl). One aim of the campaign was to perform the size-resolved chemical analysis of single particles under conditions of the free troposphere in real-time. Evaluation of single particle spectra measured predominantly in the size range between 0.5 and 5μm and determination of spectra patterns of the most frequent particle classes showed a great variability ranging from pure carbon particles over carbon particles internally mixed with salts and/or secondary components to mineral dust particles. Such mineral particles sometimes showed internal mixtures with carbon indicating scavenging effects of carbonaceous material by minerals. This can be due to coagulation or condensation of organic molecules on the mineral particles. Observation of internally mixed carbon particles is an indication for atmospheric transformation processes of pure carbon particles. Such internally mixed particles can strongly influence cloud formation due to an increase in particle size and hygroscopicity.
High abundance of mineral and carbon-containing particles could be correlated to enhanced light absorption and light scattering coefficients, respectively. Semi-quantitative evaluation of mass spectra using relative sensitivity factors showed comparable ratios of selected ion pairs compared to bulk concentrations determined by ion chromatography.