Airplane Soot Chemical Composition Analysis by Laser Desorption and Secondary Ions Mass Spectrometry

The present work has been performed in the framework of the French national project MERMOSE, which aims to characterize the soot emissions from airplane engines and to determine their role in the formation of cirrus clouds. A first sampling campaign performed on the PowerJet SaM-146 turbofan (SNECMA/Saturn) provided soot particles collected on quartz fiber filters in four engine regimes (30 %, 70 %, 85 % and 100 %). Two-Step (Desorption/Ionization) Laser Mass Spectrometry (L2MS) and Time of Fight Secondary Ion Mass Spectrometry (ToF-SIMS) techniques were used to analyze the surface chemical composition of the soot particles, with special focus on PAHs. In L2MS, the adsorbed phase is probed by nanosecond laser desorption (532nm), then the ejected molecules are ionized with a second ns laser (266nm) and further mass-separated by ToF-MS.