AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Sources of primary and secondary organic aerosol during the Southeast Atmosphere Study
ELIZABETH STONE, Anusha Priyadarshani Silva Hettiyadura, John Groenenboom, Thilina Jayarathne, University of Iowa
Abstract Number: 319 Working Group: Air Quality and Climate in the Southeast US: Insights from Recent Measurement Campaigns
Abstract To evaluate anthropogenic influences on secondary organic aerosol (SOA) formation in the southeastern United States, ambient PM2.5 samples were collected in Centerville, Alabama from June 1 to July 15 in 2013. Elemental and organic carbon (EC and OC) and organic molecular markers were measured on daytime (08:00-19:00) and nighttime (20:00-07:00) samples. OC levels ranged from 0.9 – 6.0 ug/m3 (averaging 3.0 ug/m3) while EC ranged from < 0.05 to 0.4 ug/m3 (averaging 0.14 ug/m3). The average OC to EC ratio was 22, reflecting a strong contribution from non-combustion (i.e. secondary) sources. Levoglucosan, a marker for biomass burning, concentrations ranged from 3 – 106 ng/m3; the six concentration maxima occurred during the nighttime due to more stable boundary layer conditions. Assuming that biomass burning emissions were open-burning in nature, this source was estimated to account for 1.3 to 45% of OC (averaging 8%). Alkanes, reminiscent of vegetative detritus, revealed an odd-carbon preference (ranging from 1.4 – 7.7 and averaging 3.1), reflecting the presence of primary biogenic aerosol in PM2.5. Tracers for isoprene-derived SOA (i.e. 2-methylglyceric acid and 2-methyltetrols) were among the most abundant organic species detected. Pinonic acid, a tracer for monoterpene-derived SOA, revealed a striking diurnal variation with peak concentrations observed during the day, indicative of their photochemical origin. Aromatic acids and dicarboxylic acids also peaked during the daytime. Results from molecular-marker based source apportionment to quantify absolute and relative contributions of primary and secondary sources to ambient OC will also be discussed.