AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Uptake of Organic Compounds from Ultra-Low Sulfur Diesel (ULSD) Exhaust onto Laboratory Generated Inorganic Seed Particles
ZAMIN KANJI, John Liggio, Katherine Hayden, Tak Chan, Marie-Josee Poitras, Shao-Meng Li, Environment Canada
Abstract Number: 463 Working Group: Aerosol Chemistry
Abstract Airborne particulate matter is can pose serious health risks and have a large influence on the Earth’s climate. Knowledge of the composition of atmospheric particles is crucial to be able to predict air quality as well as the composition of the troposphere. In particular, atmospheric particles can play an important role in re-distributing semi-volatile organic compounds at source through either condensational or reactive uptake. In this work we seek to study the interactions of ULSD exhaust on pre-existing acidic sulfate, ammonium nitrate and ammonium sulfate seed particles using high resolution aerosol mass spectrometry. Primary particles emitted from the exhaust were filtered out so as to observe the partitioning of gas phase species onto the seed particles as a function of dilution and reaction time. Atomized and size selected seed particles with a diameter of approximately 300 nm were mixed with particle-free diesel exhaust and introduced into a flow tube with the option of 6 sampling ports along the length of the flow tube representing an exposure time of approximately 1 – 10 minutes. Preliminary aerosol mass spectrometry results indicate that a significant amount of organic mass is taken up by the acidic seed when sampled at shorter or longer residence times in the flow tube downstream of the engine. Similar ratios of organics to sulfate obtained at both residence times are indicative of a fast reaction time. The organic mass partitioning to the condensed phase scaled with sulfate mass detected indicating diffusion into the particle rather than pure surface condensation. Additionally, for the neutral aerosol particles, a negligible amount of organic uptake was observed. Results from the effect of dilution on partitioning will also be presented. The results suggest that acidic particles will play a role in the partitioning of volatile and semi-volatile organic compounds in the atmosphere.