Impact/Purpose:

Volatile and semi-volatile organic compounds (VOCs and SVOCs) include known air toxics and contribute to the formation of ozone and organic aerosol. The important link between SVOCs, present in conventional vehicle exhaust, and secondary organic particulate matter (PM_2.5) remains poorly characterized. New analytical techniques for real-time measurement of SVOCs are required both to better understand the processes controlling production of PM_2.5 and to develop effective regulatory strategies. In addition, the effect of increased use of alternative fuels (e.g. ethanol and biodiesel) on secondary particulate matter is unknown. The goal of this research is the development a of direct method for measurement of SVOCs in vehicle exhaust by Proton Transfer Reaction Mass Spectrometry (PTR-MS) a compact, roadside-deployable that requires no sample preparation. Once tested in the lab, the technique will be used to characterize and compare the exhaust from vehicles powered by both conventional and alternative fuels utilizing a compact dilution chamber. Dilution chamber studies will be followed by roadside deployment and measurement of SVOCs.

Description:

This study will result in the development of a new method for the rapid measurement of SVOCs. The characterization of VOC and SVOC emissions of vehicles with different fuel types will improve our understanding of the processes leading to secondary organic aerosol pollution and enhance our ability to model, regulate, and reduce both VOC and PM_2.5 pollution. The new techniques and equipment developed during this study will provide ample opportunities for future studies and collaborations.

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SVOCs are readily monitored by PTR-MS provided they can be introduced into the drift reactor of the instrument. We propose to modify the gas inlet system of an existing PTR-MS instrument to optimize it for monitoring SVOCs. This will be achieved by replacing the current inlet with a heated, high-flow inlet with minimal surface area to minimize wall effects. The response of the new inlet to VOCs, SVOCs and temperature will be characterized using laboratory standards. A compact dilution chamber will be constructed and fitted with ports designed to optimize SVOC measurements. Exhaust from both conventional and alternative fuel powered vehicles will be evaluated in the dilution chamber. Once laboratory testing is complete, the new modifications will be field-tested at a roadside or tunnel.

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