AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Comparison of Estimates of Airmass Aging Using Particle and Other Measurements near Fort Worth, TX
BASAK KARAKURT CEVIK, Robert Griffin, Andrew Rutter, Barry Lefer, James Flynn, Saewung Kim, Rice University
Abstract Number: 424 Working Group: Urban Aerosols
Abstract The composition, concentration, and size of submicron aerosols were measured by an Aerodyne high-resolution time of flight aerosol mass spectrometer (HR-ToF-AMS) at a rural location northwest of the Dallas-Fort Worth, TX, area for the month of June 2011 with a time resolution of five minutes. A TSI, Inc., Model AE51 aethalometer using an optical absorption technique also was deployed measure black carbon (BC) concentrations. The total PM$_1 mass concentration ranged between 1.01 micro-gram/m$^3 and 17.92 micro-gram/m$^3, and the mean mass concentration was 4.92 micro-gram/m$^3.Significant variability is observed in the time series of total PM$_1 and of all four HR-ToF-AMS species, particularly between 21st and 25th of June. The average aerosol composition was dominated by organic matter (54%) and sulfate (24%).Organic aerosol concentrations were highly correlated with carbon monoxide (CO) (R$^2=0.64) and BC (R$^2=0.48), which are anthropogenic tracers.
Because of the large influence of organics on total aerosol concentration, various techniques associated with organic material are used to estimate the extent of aerosol aging. For example, the average DOA/DCO at this field site during this time was 81.97 ± 34.78 micro-gram/ (m$^3 ppmv), which is a typical value for an aged air mass. Other metrics of age include the ratio of OOA2 to OOA1 (more oxidized to less oxidized material), the ratio of sulfate to sulfur dioxide, the ratio of isoprene to its oxidation products, and the ratio of NO$_x to NO$_y. All metrics point to an aged air mass, but variations in these age matrices help determine the relative contributions of biogenic versus anthropogenic precursors to organic aerosols at the site.