AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Sources and Composition of Aerosol Measured near Houston, TX: Anthropogenic-biogenic Interactions
JEFFREY BEAN, Cameron Faxon, Puneet Chhabra, Manjula Canagaratna, Lea Hildebrandt Ruiz, University of Texas at Austin
Abstract Number: 330 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Particulate matter was measured in Conroe, TX (~ 70 km north of downtown Houston) during the September 2013 DISCOVER-AQ campaign. The measurement site is influenced by high biogenic emissions as well as transport of anthropogenic pollutants from the Houston metropolitan area and is therefore an ideal location to study anthropogenic-biogenic interactions. Data from and Aerosol Chemical Speciation Monitor (ACSM) suggest that on average 72 percent of non-refractory PM1 was organic material, including a high fraction of organic nitrates. There was little diurnal variation in the concentrations of ammonium sulfate; however, concentrations of organic and organic nitrate aerosol, were consistently higher at night than during the day. Potential explanations for the higher organic aerosol loadings at night include increased partitioning to the particle phase at lower temperatures and differences between daytime and nighttime chemical processes. We discuss and analyze these and other possibilities.
Positive matrix factorization applied to the organic aerosol mass spectra measured by the ACSM suggest that the measured aerosol was well mixed and highly processed, which is not surprising considering the distance of the site to major aerosol sources, as well as the high photochemical activity. While the organic aerosol was mostly composed of oxygenated organic aerosol, the influence of OA from biomass burning activity is also noticed, as also evidenced from gas-phase species measured by a High Resolution Time of Flight Chemical Ionization Mass Spectrometer (HR-ToF-CIMS) using negative (IH2O-) ionization.