Abstract

Abstract. Oxidative processing of aircraft turbine-engine exhausts was studied using a potential aerosol mass (PAM) chamber at different engine loads corresponding to typical flight operations. Measurements were conducted at an engine test cell. Organic gases (OGs) and particle emissions pre- and post-PAM were measured. A suite of instruments, including a proton-transfer-reaction mass spectrometer (PTR-MS) for OGs, a multigas analyzer for CO, CO2, NOx, and an aerosol mass spectrometer (AMS) for nonrefractory particulate matter (NR-PM1) were used. Total aerosol mass was dominated by secondary aerosol formation, which was approximately 2 orders of magnitude higher than the primary aerosol. The chemical composition of both gaseous and particle emissions were also monitored at different engine loads and were thrust-dependent. At idling load (thrust 2.5–7 %), more than 90 % of the secondary particle mass was organic and could mostly be explained by the oxidation of gaseous aromatic species, e.g., benzene; toluene; xylenes; tri-, tetra-, and pentamethyl-benzene; and naphthalene. The oxygenated-aromatics, e.g., phenol, furans, were also included in this aromatic fraction and their oxidation could alone explain up to 25 % of the secondary organic particle mass at idling loads. The organic fraction decreased with thrust level, while the inorganic fraction increased. At an approximated cruise load sulfates comprised 85 % of the total secondary particle mass.

Highlights

  • Airport activities emit both particulate and gaseous emissions (Unal et al, 2005; Hudda et al, 2014) and are a significant source of local gas- and particle-phase pollutants (Westerdahl et al, 2008)

  • primary aerosol (PA) and secondary aerosol (SA) precursor emissions such as nonmethane organic gases (NMOGs) strongly depend on aircraft engine operating conditions (Kinsey et al, 2010), e.g., the black carbon (BC) emission index (EI, g kg−1 fuel) of a gas-turbine engine is usually higher at cruise climb-out and take-off loads than at lower loads used at idle, taxi (7 %) and approach (30 %) (Liati et al, 2014; Brem et al, 2015)

  • The evolution of the chemical composition of the primary organic gases and NR-PM1 components with increasing OH exposure is shown in Fig. 2 for engine idling operation

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Summary

Introduction

Airport activities emit both particulate and gaseous emissions (Unal et al, 2005; Hudda et al, 2014) and are a significant source of local gas- and particle-phase pollutants (Westerdahl et al, 2008). Single-ring aromatics are traditionally thought to be the most important secondary organic aerosol (SOA) precursors from combustion emissions While this has been shown to be the case for some emissions, e.g., from twostroke engines (Platt et al, 2014), in other cases nontraditional precursors were assessed to be responsible for the bulk of the SOA mass formed, e.g., for biomass smoke (Bruns et al, 2016) or on-road vehicles (Platt et al, 2013, 2017; Pieber et al, 2017). The impact of these emissions and their SOA potential in typical urban atmospheres, at the proximity of airports is assessed and compared to other mobile sources

Experimental setup
PTR-ToF-MS
Data analysis
SOA formation as a function of OH exposure
Particle and gaseous emissions as a function of engine load
Precursor gases of SOA: idling
SOA formation at an approximated cruise load
Conclusions and implications for ambient air quality

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