Hyytiälä SMEAR II, Finland

SMEAR II station of University of Helsinki is located inside a Finnish boreal forest. It is the most well equipped atmospheric monitoring station in the world. Boreal forests cover almost 10% of the Earths land surface and emissions of organic vapours by trees form a major source of secondary organic aerosol in the northern hemisphere. Resolving the details of cluster and new particle formation process in the boreal forest is therefore high on our priority list.

Our group has had several smaller and larger field campaigns at SMEAR II and right now we are running continuos measurements of particle precursor vapours with two CI-APi-TOF mass spectrometers – one located at the ground level and one above the canopy. Soon we will start continuous measurements of ion clusters with the instruments also.

There are several major advances our investigations in Hyytiälä have contributed. We have obtained information on very early steps of cluster formation and early growth and found a previously unknown, but in boreal forest the most important, group of particle precursor vapours, so called Highly Oxidized Multifunctional organics (HOM) also known as Extremely Low Volatile Organic Compounds (ELVOC). From Smear II, we also for the first time discovered the atmospheric presence of stabilised Criegee Intermediates (sCI), important for the gas phase sulphuric acid budgets, and thus for the cluster and new particle formation process.

Campaign in 2011, was the first where our spear head instrument, CI-APi-TOF, that has subsequently became the main tool in all of our research breakthroughs, was deployed.