AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Effect of Titanium Dioxide Particles on Secondary Organic Aerosol Formation from Photooxidation of Toluene
TIANQU CUI, Richard Kamens, Joe Pedit, Jason Surratt, Ilona Jaspers, Kenneth Sexton, University of North Carolina at Chapel Hill
Abstract Number: 664 Working Group: Aerosol Chemistry
Abstract Nanomaterials represent an emerging field of technological innovation and industrial manufacture. Most synthetically produced nanomaterials are particles that have at least one dimension on the order of 1 to 100 nm, which are designed to possess enhanced catalytic activities compared to atmospheric particulate matter. Because most engineered nanoparticles are made through gas-phase processes, industrial emissions of these reactive materials, such as metal oxides, will be present in the local troposphere. Subsequently, these nanoscale catalysts may rapidly coagulate with pre-existing ambient aerosol, or serve as aerosol surfaces for heterogeneous nucleation of secondary organic aerosol (SOA). However, the atmospheric role of engineered nanoparticles and their detrimental health effect remain unclear due to the lack of systematic experimental studies conducted under more realistic atmospheric conditions of full spectrum sunlight and natural variation of temperature and humidity.
Since engineered nanoparticles are expected to have unique enhanced reactivity and potential photocatalytic properties as a nucleation surface in urban and rural environments, in this study, outdoor smog chamber experiments using natural diurnal sunlight, temperature and humidity, of toluene photooxidation in presence of nitric oxide were systematically conducted to investigate the effect of the pre-existing titanium dioxide (TiO2) seed aerosol, as an instance of widely used engineered metal oxide nanomaterials. Our preliminary results indicate that compared with ammonium sulfate as pre-existing particles, TiO2 enhanced and accelerated SOA formation from toluene photooxidation, potentially due to the photocatalytic formation of the reactive oxygen species, for example, hydroxyl radicals as the primary oxidant in lower atmosphere, when TiO2 is exposed to near-ultraviolet light.