AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Comparison of the Observed Organosulfates (IEPOX Sulfate and GA Sulfate) in the Southeast US to the Western US during DC3 and SEAC4RS
JIN LIAO, Karl D. Froyd, Daniel Murphy, Frank Keutsch, Ge Yu, Paul Wennberg, Jason St. Clair, John Crounse, Armin Wisthaler, Tomas Mikoviny, Jose-Luis Jimenez, Pedro Campuzano-Jost, Douglas Day, CU CIRES- NOAA ESRL
Abstract Number: 142 Working Group: Air Quality and Climate in the Southeast US: Insights from Recent Measurement Campaigns
Abstract Organosulfates are important secondary organic aerosol (SOA) components and are good tracers for aerosol heterogeneous reactions. However, quantification of organosulfates is challenging, and as a result our knowledge about their spatial distribution, formation conditions, and environmental impact is limited. In this study, we report the airborne measurements of two organosulfates, a relatively well-known isoprene derived IEPOX-sulfate and a newly identified and quantified glycolic acid (GA) sulfate, by the NOAA Particle Analysis by Laser Mass Spectrometer (PALMS) onboard the NASA DC8 aircraft over the continental US during DC3 and SEAC4RS campaigns. IEPOX sulfate accounted for about 1-1.5% of aerosol mass loading on average near the ground in the Southeast US and decreased dramatically in the western US (0.2-0.4%) and in upper troposphere and lower stratosphere (<0.2%). Compared to IEPOX sulfate, the observed GA sulfate is more uniformly distributed, present from lower troposphere (0.2-0.6% of aerosol mass) to upper troposphere (0.7%), to even lower stratosphere (0.7%). Considering the spatial distribution, GA sulfate may be even more abundance than IEPOX sulfate globally. Ambient measurements confirmed that IEPOX sulfate is formed from isoprene oxidation and is an indicator for isoprene SOA formation. Acidity is critical for both organosulfates and largely drives GA sulfate formation at high altitudes. The organic precursors of GA sulfate may include glycolic acid and likely have both biogenic and anthropogenic sources. GA sulfate in the upper troposphere and lower stratosphere is probably formed in situ and provide ambient evidence for the formation of SOA at high altitudes. This study suggests that besides the emission of organic precursors, emission control of SO2 and NH3, which largely govern the aerosol acidity, would largely affect the formation of SOA compounds such as organosulfates.