AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Characterization of Ambient Aerosol Concentration, Composition, and Aging during the Southern Oxidant and Aerosol Study
BASAK KARAKURT CEVIK, Yu Jun Leong, Carlos Hernandez, Robert Griffin, Rice University
Abstract Number: 450 Working Group: Source Apportionment
Abstract The Southern Oxidant and Aerosol Study (SOAS) took place in Centerville, AL, over a six-week period during June and July 2013 and included ground and elevated measurements that aimed to improve the understanding of biosphere-atmosphere interactions and their impacts on air quality and climate. As part of SOAS, an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was deployed. The HR-ToF-AMS provided quantitative measurement of non-refractory submicron aerosol composition with high temporal resolution. The average aerosol concentration over the campaign was dominated by organic aerosol (OA) (72.6%). The time series of the ratio of the mass concentration of OA to the increase of carbon monoxide over background (∆CO) (OA/∆CO) and the relationships between OA/∆CO and metrics of photochemical airmass age (based on oxidation of nitrogen oxides and sulfur dioxide) are reported. The OA/∆CO diurnal profile shows a photochemical profile with an increase starting at ~0700 CST, a peak at ~1300 CST, and a decrease until ~1630 CST. Increases in OA/∆CO are observed with increasing -log (NO $_x/NO $_y) values, up to a threshold value. The OA/∆CO values decrease after this point, which might mark a point where further aging leads to a decrease in OA due to fragmentation and volatilization. A larger initial slope was observed with lower SO $_4 $^(2−)/(SO $_2 + SO $_4 $^(2−)) values, which may signify more rapid OA processing under fresh plume conditions. For a better understanding of OA sources and processing, PMF source attribution analysis is investigated.