1Particle Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
2Institute for Atmospheric Physics, Johannes Gutenberg University, Mainz, Germany
3Institute for Energy- and Climate Research Troposphere (IEK-8), Research Center Jülich GmbH, Jülich, Germany
4Leibniz Institute for Tropospheric Research, Leipzig, Germany
5Department of Atmospheric Science, Colorado State University, Fort Collins, USA
6Department of Marine Earth and Atmospheric Science, North Carolina State University, Raleigh, USA
7Institute for Atmospheric and Climate Science, ETH Zürich, Zürich, Switzerland
Abstract. The ability of coated mineral dust particles to act as cloud condensation nuclei (CCN) and ice nuclei (IN) was investigated at LACIS (Leipzig Aerosol Cloud Interaction Simulator) during the FROST1- and FROST2-campaigns (Freezing of dust). Sulphuric acid was condensed on the particles which afterwards were optionally humidified, treated with ammonia vapour and/or heat. By means of aerosol mass spectrometry we found evidence that processing of mineral dust particles with sulphuric acid leads to surface modifications of the particles. These surface modifications are responsible for the observed reduction of the IN activation of the particles. The observed particle mass spectra suggest that different treatments lead to different chemical reactions on the particle surface. Possible chemical reaction pathways and products are suggested and the implications on IN and CCN efficiency of the treated dust particles are discussed.