Article pubs.acs.org/est
Characterization of Gas-Phase Organics Using Proton Transfer Reaction Time-of-Flight Mass Spectrometry: Aircraft Turbine Engines Dogushan Kilic,† Benjamin T. Brem,‡,§ Felix Klein,† Imad El-Haddad,† Lukas Durdina,‡,§ Theo Rindlisbacher,∥ Ari Setyan,‡,§ Rujin Huang,† Jing Wang,‡,§ Jay G. Slowik,† Urs Baltensperger,† and Andre S. H. Prevot*,†,⊥ †
Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland Laboratory for Advanced Analytical Technologies, Empa, 8600 Dübendorf, Switzerland § Institute of Environmental Engineering, ETH Zurich, 8093, Zurich, Switzerland ∥ Federal Office of Civil Aviation, 3003 Bern, Switzerland ‡
S Supporting Information *
ABSTRACT: Nonmethane organic gas emissions (NMOGs) from in-service aircraft turbine engines were investigated using a proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS) at an engine test facility at Zurich Airport, Switzerland. Experiments consisted of 60 exhaust samples for seven engine types (used in commercial aviation) from two manufacturers at thrust levels ranging from idle to takeoff. Emission indices (EIs) for more than 200 NMOGs were quantified, and the functional group fractions (including acids, carbonyls, aromatics, and aliphatics) were calculated to characterize the exhaust chemical composition at different engine operation modes. Total NMOG emissions were highest at idling with an average EI of 7.8 g/kg fuel and were a factor of ∼40 lower at takeoff thrust. The relative contribution of pure hydrocarbons (particularly aromatics and aliphatics) of the engine exhaust decreased with increasing thrust while the fraction of oxidized compounds, for example, acids and carbonyls increased. Exhaust chemical composition at idle was also affected by engine technology. Older engines emitted a higher fraction of nonoxidized NMOGs compared to newer ones. Idling conditions dominated ground level organic gas emissions. Based on the EI determined here, we estimate that reducing idle emissions could substantially improve air quality near airports.
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INTRODUCTION Most emissions of nonmethane organic gases (NMOGs) at airports come from aircraft turbine engines during flight-related operations.1 These emissions, including oxygenated species and both saturated and unsaturated hydrocarbons, potentially impact human health by inhibiting respiratory function or serving as precursors for ozone and secondary organic aerosol production, which has a variety of harmful effects.2−7 For example, NMOGs observed at airports include polycyclic aromatic hydrocarbons (PAHs),8 which have been identified as carcinogens in animal experiments and epidemiological studies,9,10 and may increase childhood obesity risk upon maternal exposure.11 Air pollution from aircraft emissions is a concern not only within the airport itself but also in surrounding regions.12,13 For example, hospital admissions for respiratory conditions were found to be significantly higher for residents living within five miles of three airports in New York State compared to those living farther than five miles away.14 NMOG emission inventories are based on engine emissions certification data for an idealized landing and takeoff cycle (LTO). The LTO defined by the International Civil Aviation © XXXX American Chemical Society
Organization (ICAO) consists of four operating modes defined by thrust setting and time in each mode. These operating modes represent idling (7%), approach (30%), climb-out (85%), and takeoff (100%), respectively. Engine emissions calculated with the LTO cycle are then used to verify that engines comply with regulatory emission limits. Although not originally intended for quantitative assessment of airport air quality, the ICAO LTO cycle and standard atmosphere emission factors are often used to generate airport emission inventories below 3000 ft (∼915 m).15 Emissions of organic gases by aircraft engines are highest on the ground at low power settings (thrust
