Capturing the pristine atmosphere.

Present-day observations may allow to approximate clean atmospheric concentrations, if performed in regions where anthropogenic influence is minimum. For terrestrial regions, this has so far only been attempted for one tropical rainforest site.

It is questionable though, whether these observations can be taken to represent clean air conditions elsewhere e.g., the circumpolar boreal forests of the northern hemisphere. Large differences in vegetation and climate that substantially affect trace gas emissions and their atmospheric reactions render this unlikely.

The chief objectives of this project therefore are to

• obtain a comprehensive data set of climatically relevant atmospheric aerosol precursor (volatile organic compound, VOC) concentrations and fluxes, and aerosol number concentration and size distribution from northern hemisphere continental environment with least possible anthropogenic impact,
• test whether unpolluted boreal and tropical regions differ in terms of physical SOA properties and
• to quantify if and how boreal-tropical SOA differences may be related to differences in biogenic precursor emissions.