Abstract
Abstract. Toluene and other aromatics have long been viewed as the dominant anthropogenic secondary organic aerosol (SOA) precursors, but the SOA mass yields from toluene reported in previous studies vary widely. Experiments conducted in the Carnegie Mellon University environmental chamber to study SOA formation from the photo-oxidation of toluene show significantly larger SOA production than parameterizations employed in current air-quality models. Aerosol mass yields depend on experimental conditions: yields are higher under higher UV intensity, under low-NOx conditions and at lower temperatures. The extent of oxidation of the aerosol also varies with experimental conditions, consistent with ongoing, progressive photochemical aging of the toluene SOA. Measurements using a thermodenuder system suggest that the aerosol formed under high- and low-NOx conditions is semi-volatile. These results suggest that SOA formation from toluene depends strongly on ambient conditions. An approximate parameterization is proposed for use in air-quality models until a more thorough treatment accounting for the dynamic nature of this system becomes available.
Highlights
Fine particles affect climate (IPCC, 2007) and human health (Dockery et al, 1993; Davidson et al, 2005)
Most of the oxygenated organic aerosol (OOA) is expected to be secondary organic aerosol (SOA), which is produced when volatile organic compounds (VOCs) or semi-volatile organic compounds (SVOCs) are oxidized in the gas phase, forming less volatile products that can partition to the particle phase
The SOA yields from the photo-oxidation of toluene are higher than previously reported values
Summary
Fine particles affect climate (IPCC, 2007) and human health (Dockery et al, 1993; Davidson et al, 2005). The organic component of aerosol particles comprises about one half of the fine-particle mass on average (Kanakidou et al, 2005; Zhang et al, 2007). Most of the OOA is expected to be secondary organic aerosol (SOA), which is produced when volatile organic compounds (VOCs) or semi-volatile organic compounds (SVOCs) are oxidized in the gas phase, forming less volatile products that can partition to the particle phase. SOA is expected to comprise a significant fraction of the atmospheric fine-particle mass. Air-quality models currently under-predict the concentrations of organic aerosol in the atmosphere, especially in the summer and in urban areas (Volkamer et al, 2006; Goldstein and Galbally, 2007; Karydis et al, 2007), suggesting that we do not understand anthropogenic SOA formation well
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
