Meinrat O Andreae, Scripps Institution of Oceanography, UCSD, La Jolla, United States; Max Planck Institute for Chemistry, Biogeochemistry Department, Mainz, Germany, Tracey W Andreae, Max Planck Institute for Chemistry, Mainz, Germany and Florian Ditas, Max Planck Institute for Chemistry, Multiphase Chemistry Department, Mainz, Germany