Abstract Number: 712 Working Group: Source Apportionment
Abstract Semivolatile organic compounds (SVOCs) represents a dominant category of secondary organic aerosol (SOA) precursors that are missing in most air quality models. In the present study, an experimental system was developed and applied to a light-duty diesel engine to determine the emission factors of SVOCs and nonvolatile particulate matter (PM) components using ultra-low-sulfur diesel (ULSD) and three biodiesels, at dilution ratios representative of ambient conditions. For ULSD, the contribution of SVOCs to total OM mass in the engine exhaust could be as high as 85%. Evaporation of SVOM from diesel particles during dilution led to decreases in the hydrogen to carbon ratio of organic matter (OM) and the number emission factor of the particles. Substituting biodiesels for ULSD could increase SVOCs emissions but brought large reductions in black carbon (BC) emissions. Among the biodiesels tested, tallow/used cooking oil (UCO) biodiesel showed reductions over soybean and canola biodiesels in terms of both SVOCs and nonvolatile PM emissions. It is noteworthy that PM properties, such as particle size and BC mass fraction, could differ substantially between emissions from conventional diesel and biodiesels.