Paul Scherrer Institut (2009, 2011, 2013)
The PSI campaigns have been focused on secondary organic aerosol formation from glyoxal by multiphase processing. Glyoxal (C2H2O2) is a small molecule that cannot partition to aerosol based on vapor pressure because it is too volatile. However, it is extremely water-soluble and can partition to the aerosol aqueous phase based on Henry’s law. Once in the aqueous phase, it can undergo multiphase reactions (e.g. with aqueous-phase OH and NH4+) to form secondary organic aerosol mass. See: Ervens and Volkamer (2010) ACP.
The Paul Scherrer Institut chamber is a 27 m3 temperature-controlled Teflon chamber. It is equipped with UV and visible lights and a suite of aerosol instrumentation. During our experiments, CU has brought CD-DOAS instruments for highly time-resolved glyoxal and NO2 quantification.
Our results from the 2011 campaign show that the Henry’s law value for glyoxal is dependent on the aerosol sulfate concentration. Electrostatic interactions between glyoxal and the sulfate increase the glyoxal partitioning to the aerosol aqueous phase as the sulfate concentration increases. However, beyond a certain point, this results in a kinetic limitation and partitioning is no longer enhanced with increasing sulfate. Additionally, reversible glyoxal uptake can be described by two pools: pool one (monomers and monomeric hydrates) forms with a time constant of ~100 seconds, while pool two (reversibly-formed oligomers) forms with a time constant of ~10,000 seconds. See: Kampf et al. (2013) ES&T.
Our 2013 campaign, scheduled for May-June 2013, will focus on expanding these results to additional seed types and study the reversibility of glyoxal formation.