AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Temperature Effects on Secondary Organic Aerosol Formation from Gasoline Vehicle Exhaust
MARY KACARAB, David R. Cocker III, University of California, Riverside
Abstract Number: 272 Working Group: Combustion
Abstract Exhaust from gasoline vehicles has recently been targeted as a potential significant source for anthropogenic secondary organic aerosol (SOA). This work quantifies the significant effects of environmental temperature on SOA formation from gasoline vehicle emissions. SOA from oxidized gasoline vehicle exhaust was studied in the University of California Riverside (UCR) College of Engineering Center for Environmental Research and Technology (CE-CERT) dual 90m$^3 environmental chambers in a series of experiments ranging in temperature from 5$^OC to 40$^OC. Aerosol size distribution, number and mass concentrations, volatility, density, and fractal dimensions were measured over the course of aging and through different temperature change cycles. Aerosol formed at the "cold" temperature of 5$^OC gave a 1.4x greater yield than aerosol formed at the "hot" temperature of 40$^OC. Significant aerosol mass is lost from the system when SOA formed at 5$^OC is heated to 40$^OC, however no aerosol mass is gained when SOA formed at 40$^OC is cooled to 5$^OC. The density and fractal dimension of the particles are also affected by temperature, with cold temperature aerosol having a density of ~2g/cm$^3 yet decreasing to ~1.5g/cm$^3 when temperature is increased to 40$^OC. For hot temperature aerosol, the density remains constant at ~1.5g/cm$^3 even when cooled. The results of these experiments indicate a clear hysteresis effect in aerosol mass, density, and fractal dimension as well as the presence of thermally labile compounds in gasoline vehicle exhaust. The effect of temperature seen on vehicle exhaust aerosols does not follow the same trends observed for biogenic aerosols.