(160c) Changes in Water-Soluble Particulate Composition From Vehicles

Particle number, size, and composition information is important for constraining aerosol effects on air quality, climate, and health. The composition of particles, especially from vehicular sources, may contain insoluble material that may modify particle nucleating properties.  Changes in fuel properties are known to modify criteria pollutants and particulate matter mass, size, and number.  In this work we summarize findings as they pertain to the water-soluble and insoluble composition of particles. In field measuremnts and controlled laboratory studies, a water-based condensation particle counter (CPC) and a butanol-based CPC measure particle number concentration. Both instruments were coupled with a Scanning Mobility Particle Sizer (SMPS) and particle number and size data were recorded.  Real time particle insoluble mass fractions are estimated with the SMPS data sets; theoretical soluble fractions are calculated from ideal hygroscopicty single parameter values.  This is the first time that this experimental method has been employed and used to infer online insoluble fractions.  The results show that near-roadway emissions contain water insoluble and black carbon components. The emissions of  different ethanol and butanol gasoline blends are also explored for light-duty vehicles on a light-duty dynaometer chassis.  Laboratory results indicate that soluble vehicular components are strongly correlated with vehicle driving conditions.