Open Access

Boris Bonn, Shang Sun, Werner Haunold, Robert Sitals, Eric van Beesel, Luis dos Santos, Björn Nillius, Stefan Jacobi

• The anthropogenic influence on climate and environment has increased strongly since industrialization about 150 yr ago. The consequences for the atmosphere became more and more apparent and nowadays affect our life quality on Earth progressively. Because of that it is very important to understand the atmospheric processes, on which these effects are based on, in detail. In this study we report the set-up of a novel twin chamber technique that uses the comparative method and establishes an appropriate connection of atmospheric and laboratory methods to broaden the tools for investigations. It is designed to study the impact of certain parameters and gases on ambient processes such as particle formation online and can be applied in a large variety of conditions. The characterisation of both chambers proved that both chambers operate identically with a residence time (xT (COMPASS 1) = 26.5 ± 0.3 min and xT (COMPASS 2) = 26.6 ± 0.4 min) at a typical flow rate of 15 L min−1 and a deposition rate (1.6 ± 0.8) × 10−5 s−1. Comparison measurement showed no significant differences. Therefore operation under atmospheric conditions is trustworthy. To indicate the applicability and the benefit of the system a set of experiments was conducted at different conditions, i.e. urban and remote, enhancing ozone and terpenes as well as reducing sunlight. In the ozone enhanced ambient particle number and volume increased substantially at urban and remote conditions in a different strength. Solar radiation displayed a clear positive effect on particle number as well as terpene addition did at remote conditions. Therefore the system is a useful tool to investigate local precursors, the details of ambient particle formation at surface locations as well as future feedback processes.