AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Assessment of Biogenic Secondary Organic Aerosol in the Himalayas
ELIZABETH STONE, Tony Nguyen, Bidya Banmali Pradhan, Pradeep Man Dangol, University of Iowa
Abstract Number: 178 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Biogenic contributions to secondary organic aerosol (SOA) in the Southeast Asian regional haze were assessed by measurement of particle-phase isoprene, monoterpene, and sesquiterpene photooxidation products in fine particles (PM2.5) at a mid-latitude site in the Himalayas. Organic species were measured in solvent-extracts of filter samples using gas chromatography mass spectrometry (GCMS) and chemical derivatization; this analysis was used to quantify molecular markers for primary aerosol sources—including motor vehicles, biomass burning, and detritus—and SOA tracers. Authentic standards of most SOA products were not commercially available at the time of this study, so surrogate standards were used for semi-quantitation. Using an empirical approach to uncertainty estimation based on homologous series of atmospherically-relevant model compounds, analytical uncertainties ranged from 32% for SOA tracers with structurally-similar surrogates to more than 100% for tracers with a poorly-matched surrogate. Biogenic SOA contributions to PM2.5 mass and organic carbon content in the 2005 monsoon and post-monsoon season ranged from 2-19% for isoprene, 1-5% for monoterpenes, and 1-4% for sesquiterpenes. High concentrations of isoprene derivatives in aerosol, particularly in the late summer months, point to biogenic SOA as a significant source of organic carbon in the Himalayan region.