Hourly Speciated Organic Aerosol Composition in Riverside, CA during SOAR 2005

Thermal Desorption Aerosol GC/MS-FID (TAG) is a new in-situ instrument to identify and quantify organic aerosol chemical composition with one hour time resolution. Atmospheric particles are collected by means of humidification and inertial impaction. The sample is then thermally desorbed onto a GC column, where it is separated into individual compounds which are identified and quantified using a quadrupole mass spectrometer (MS) and flame ionization detector (FID). With the exception of periodic manually applied calibration standards, TAG is fully automated, offering around the clock measurements to determine diurnal, weekly, and seasonal patterns in organic aerosol composition. The summer and fall of 2005 offered a unique opportunity for TAG to operate in parallel with a large suite of organic aerosol instrumentation, including several Aerodyne AMS instruments, three ATOFMS instruments, several high volume filter samplers, two EC/OC monitors, along with other aerosol and gas phase instrumentation as part of the Study of Organic Aerosol at Riverside (SOAR) campaign at the University of California, Riverside. We will present initial TAG particle source apportionment results, including separation of the influence from particle sources such as biomass combustion, vehicle emissions, pesticides, biogenic aerosol, and oxidation of biogenic and anthropogenic precursor gases leading to secondary organic aerosol (SOA) formation. We will also present ambient air observations of gas-particle partitioning as a function of molecular size and functional groups.