Secondary organic aerosol formation from alkane oxidation

Description

Long-chain alkanes represent an important class of precursors to atmospheric secondary organic aerosol (SOA) and therefore as contributing to the global burden of organic aerosol. Alkanes are the dominant component of the Unresolved Complex Mixture, which is thought to represent a large part of the unaccounted-for source of ambient SOA. We report here on comprehensive laboratory chamber experiments aimed at understanding both the detailed chemistry of formation and aging of alkane SOA as well as the overall yield of aerosol and its dependence on alkane structure. The chamber experiments were carried out for a 36-hour duration, thus capturing several generations of oxidation. Simultaneous measurements with a Chemical Ionization Mass Spectrometer and an Aerodyne High-Resolution Aerosol Mass Spectrometer afford an unprecedented view of gas- and aerosol-phase chemistry that leads to the multi-functional, low volatility compounds characteristic of SOA. The experiments reported here focus on the C12 alkanes, under both high- and low-NOx conditions, characteristic of strongly anthropogenically influenced air masses and relatively pristine environments, respectively.