Chemical classes of atmospheric aerosol particles at a rural site in Central Europe during winter

Ambient atmospheric particles were studied at an ecosystem research site in the Fichtelgebirge mountains in Central Europe by single-particle analysis and bulk impactor measurements. Fuzzy clustering analysis of mass spectra of individual aerosol particles allowed chemical classification of the atmospheric aerosol. During the campaign, inorganic salts, mineral particles, and carbonaceous particles, with varying degrees of secondary components, were identified. These chemical classes exhibited preferential size ranges leading to a characteristic pattern of relative abundances with respect to particle size. A more detailed analysis revealed that 65–80% of all particles were assigned almost exclusively to one chemical class. These particle populations are assumed to be externally mixed with respect to the identified chemical classes. The temporal variations of the ratio of nitrate to ammonium (ranging between 0.37 and 0.81) determined by both impactor measurements and single-particle analyses were in good agreement. Through Monte-Carlo-type simulations, confidence intervals of the mean NO3−/NH4+ ratio were calculated for sub-samples of the total particle population.