Photochemical SOA formation in NOx-organic mixtures

Abstract

Secondary organic aerosol (SOA) is often larger than predicted from gas phase precursors and known chemistry, suggesting that there are unrecognized sources and/or chemistry occurring in urban atmospheres. Studies of SOA formation from the NOx photooxidation and ozonolysis of selected biogenic and anthropogenic precursors in a new flow system will be reported. Changes in the gas phase composition are measured using GC-MS, a NOx chemiluminescence analyzer, an O3 UV monitor, APCI-MS and PTR-MS. Particle size distributions are characterized using SMPS and APS, and light scattering is measured using a three wavelength nephelometer. The chemical composition of the particles is measured using SPLAT II and an aerosol mass spectrometer, as well as GC-MS with and without derivatization of filter-collected samples. The capabilities of this new system will be presented, along with results from the oxidation of alpha-pinene and toluene, and the implications for SOA formation and loss in the atmosphere discussed.