AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Aromatic Secondary Organic Aerosol Formation in the Presence of Sea Salt Aerosols
ROSS BEARDSLEY, Myoseon Jang, Yunseok Im, Ori Barber, Carrie Delcomyn, Ned Witherspoon, University of Florida
Abstract Number: 730 Working Group: Aerosol Chemistry
Abstract Dual, large outdoor chambers were used to investigate the effect of heterogeneous aqueous phase chemistry on the secondary organic aerosol yields of the photooxidation products of aromatic hydrocarbons in the coastal environment. Toluene and 1,3,5-trimethylbenzene were photochemically oxidized in the presence and absence of inorganic seeds (sea salt aerosols or NaCl) at low NO$_x conditions. Overall, the presence of sea salt aerosols (SSA), which were shown to contain water even at very low relative humidities, led to higher SOA yields than the presence of NaCl seeds and the seedless condition in all cases. In order to evaluate the impact of the aqueous phase reaction of aerosols on SOA yield, the aerosol organic mass (OM) was decoupled into the organic mass from partitioning (OM$_P) and the organic mass from heterogeneous aqueous phase reactions (OM$_(aq)). The results provided suggest that SOA yields in the coastal environment will be much higher than those produced in terrestrial environment. To study the effect of SOA formation on the chemical composition of SSA, inorganic species were measured using a Particle-Into-Liquid-Sampler coupled to ion chromatograph and aerosol functional groups were analyzed using a Fourier Transform Infrared (FTIR) spectrometer. The FTIR data studies also suggested that hygroscopic properties of SSA were influenced by SOA. The aged SSA gradually grows with increasing RH while the fresh SSA shows a clear phase transition. The depletion of Cl$^- ion due to the accommodation of nitric acid and carboxylic acids on the surface of SSA corresponds with changes in aerosol hygroscopic properties.