AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Closing the Gas Phase Organic Carbon Budget in Aircraft Engine Exhaust: Characterizing Low Volatility Organic Compounds (LVOCs)
EBEN CROSS, James Hunter, Jonathan Franklin, Scott Herndon, Richard Miake-Lye, Michael Timko, Yu Zhenhong, Edward Fortner, John Jayne, Douglas Worsnop, Jesse Kroll, MIT
Abstract Number: 650 Working Group: Aerosol Chemistry
Abstract Gas phase low volatility organic compounds (LVOCs) comprise an atmospherically important, largely unmeasured class of organic species in the atmosphere. LVOCs consist of intermediate volatility organic compounds (IVOCs; i.e. C13-C20) and semi-volatile organic compounds (SVOCs; i.e. C21-C32). Atmospheric oxidation of gas phase LVOCs leads to the formation of secondary organic aerosol (SOA) which in turn has direct implications for climate and human health. The rates and the chemical properties of LVOC emissions are poorly characterized and not accurately parameterized in atmospheric chemistry models.
Here we describe results from the Alternative Aviation Fuels Experiment (AAFEX-II) obtained with a recently developed technique that measures the amount, volatility and bulk composition of LVOCs. LVOCs were measured as a function of engine power and fuel type at a sampling position 143 m downwind of the NASA DC-8 aircraft. Results show that LVOC emissions are highest during low engine power operating conditions (4-7% thrust), indicating that LVOCs comprise a significant fraction (~30%) of the total hydrocarbon emissions under engine idle/taxi operation. With increasing engine power, the volatility of the LVOC emissions shift from higher to lower volatility species. Combining LVOC emission indices with VOC and PM emissions provides a more comprehensive characterization of the organic carbon emitted by aircraft engines.