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Environ Sci Technol

Title:		Evaluation of the effects of ozone oxidation on redox-cycling activity of two-stroke engine exhaust particles
Author(s):		McWhinney RD; Gao SS; Zhou S; Abbatt JP;
Address:		"Department of Chemistry, University of Toronto, Toronto, ON, Canada. rmcwhinn@chem.utoronto.ca"
Journal Title:		Environ Sci Technol
Year:		2011
Volume:		20110222
Issue:		6
Page Number:		2131 - 2136
DOI:		10.1021/es102874d
ISSN/ISBN:		1520-5851 (Electronic) 0013-936X (Linking)
Abstract:		"The effect of oxidation on the redox-cycling activity of engine exhaust particles is examined. Particles obtained from a two-stroke gasoline engine were oxidized in a flow tube with ozone on a one-minute time scale both in the presence and absence of substantial gas-phase exhaust components. Whereas ozone concentrations were high, the ozone exposures were approximately equivalent to 60 ppb ozone for 2-8 h. Oxidation led to substantial increases in redox-cycling of aqueous extracts of filtered particles, as measured using the dithiothreitol (DTT) assay. Increases in redox activity when the entire exhaust was oxidized were primarily driven by deposition of redox-active secondary organic aerosol (SOA), resulting in an upper-limit DTT activity of 8.6 +/- 2.0 pmol DTT consumed per min per microgram of particles, compared to 0.73 +/- 0.60 pmol min(-1) mug(-1) for fresh, unoxidized exhaust particles. Redox-cycling activity reached higher levels when VOC denuded exhaust was oxidized, with the highest DTT activity observed being 16.7 +/- 1.6 pmol min(-1) mug(-1) with no upper limit reached for the range of ozone exposures used in this study. Our results provide laboratory support for the hypothesis that the toxicity of engine combustion particles due to redox-cycling may increase as they age in the atmosphere"
Keywords:		Air Pollutants/analysis/*chemistry Oxidation-Reduction Ozone/*chemistry Particulate Matter/analysis/*chemistry Vehicle Emissions/*analysis Volatile Organic Compounds/analysis/chemistry;
Notes:		"MedlineMcWhinney, Robert D Gao, Shawna S Zhou, Shouming Abbatt, Jonathan P D eng Research Support, Non-U.S. Gov't 2011/02/24 Environ Sci Technol. 2011 Mar 15; 45(6):2131-6. doi: 10.1021/es102874d. Epub 2011 Feb 22"