AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Atmospheric Intermediate-volatility Organic Compounds: A Small Fraction of Atmospheric Hydrocarbons and a Large Contribution to Secondary Organic Aerosol
YUNLIANG ZHAO, Allen Robinson, Christopher Hennigan, Andrew May, Joost de Gouw, Jessica Gilman, Bill Kuster, Agnes Borbon, Carnegie Mellon University
Abstract Number: 377 Working Group: Urban Aerosols
Abstract Understanding the abundance, volatility distribution and chemical composition of atmospheric intermediate-volatility organic compounds (IVOCs) is crucial to predicting their secondary organic aerosol (SOA) production and identifying their major primary sources. In our study, atmospheric IVOCs collected in Pasadena, CA during the CalNex campaign are analyzed comprehensively. The concentrations of IVOC hydrocarbons average 6.3±1.9 µg/m-3 and 7.4 ± 1.2% of the concentrations of speciated volatile organic compounds (VOCs). Only 8.6 ± 2.2% of IVOC hydrocarbons are speciated. The remaining IVOC hydrocarbons are reported as two lumped groups of branched alkanes and unspeciated IVOC hydrocarbons and are determined as bins corresponding to n-alkanes (C12-C21). These binned and lumped groups allow more constraints on both OH reaction constant rates and SOA yields of atmospheric IVOCs. The estimated lower bound of SOA production from IVOC hydrocarbons accounts for ~30% of enhancement in SOA during the day and is over four times that from the traditional SOA precursors, light single-ring aromatics. Other primary sources in addition to on-road vehicles are indicated to significantly contribute to atmospheric IVOCs and to be petroleum-related sources.