Size and composition measurements of background aerosol and new particle growth in a Finnish forest during QUEST 2 using an Aerodyne Aerosol Mass Spectrometer

摘要

The study of the growth of nucleation-mode particles is important, as thisprevents their loss through diffusion and allows them to reach sizes wherethey may become effective cloud condensation nuclei. Hyytiue4lue4, aforested site in southern Finland, frequently experiences particlenucleation events during the spring and autumn, where particles first appearduring the morning and continue to grow for several hours afterwards. Aspart of the QUEST 2 intensive field campaign during March and April 2003, anAerodyne Aerosol Mass Spectrometer (AMS) was deployed alongside otheraerosol instrumentation to study the particulate composition and dynamics ofgrowth events and characterise the background aerosol. Despite the smallmass concentrations, the AMS was able to distinguish the grown particles inthe 100 nm regime several hours after an event and confirm that theparticles were principally organic in composition. The AMS was also able toderive a mass spectral fingerprint for the organic species present, andfound that it was consistent between events and independent of the meanparticle diameter during non-polluted cases, implying the same species werealso condensing onto the accumulation mode. The results were compared withthose from offline analyses such as GC-MS and were consistent with thehypothesis that the main components were alkanes from plant waxes and theoxidation products of terpenes.