AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
SOA Formation, CCN Activity and PAH Products during Aging of Diesel Exhaust in a Laboratory Chamber
HUMPHREY CHUKWUTO, Da' Nay Lacey, Alexis Tupy, Frank Bowman, Univeristy of North Dakota
Abstract Number: 692 Working Group: Aerosols, Clouds, and Climate
Abstract Diesel exhaust soot particles emitted into the atmosphere undergo aging that changes their physical and chemical properties, but these processes are complex and not well understood. Laboratory chamber experiments were conducted to investigate the aging of diluted diesel exhaust with and without UV light. Particle growth and changes in number concentration and size distribution were monitored with an SMPS. CCN Activity measurements helped detect changes in particle composition. Particle and gas-phase samples were also collected at the beginning and end of the experiment for quantitative GC-MS analysis of PAHs and PAH products. Aging experiments with UV light resulted in significant particle growth due to formation of SOA. Freshly emitted diesel soot particles and particles aged in the dark showed little or no CCN activity, but particles in the UV irradiated mixture showed increasing CCN activity over time. UV exposure also led to increased concentrations of hydroxy PAH products and higher oxy-PAH/PAH ratios relative to experiments in the dark. These results demonstrate that photooxidation of diesel exhaust leads to formation of more polar SOA mass, including oxidation of PAH compounds.