Photochemical aging of aviation emissions: transformation of chemical and physical properties of exhaust emissions from a laboratory-scale jet engine combustion chamber
Year: 2025
Type: article
Abstract: Aviation is an important source of urban air pollution, but the impacts of photochemical processing on the exhaust emissions remain insufficiently characterized. Here, the physical–chemical properties of fresh and photochemically aged emissions from a laboratory-scale jet engine burner operated with JP-8 kerosene were studied in detail with a range of online and offline methods. The fresh emissions contained high amounts of organic matter present predominantly in the gaseous phase. Photochemical aging in an oxidation flow reactor caused substantial formation of oxidized organic aerosol, increasing the particle mass approximately 300-fold. During aging, aromatic hydrocarbons and alkanes in the gas-phase decayed, while gas-phase oxidation products, such as small carbonyls and oxygenated aromatics, increased. The composition of organic matter became more complex by photochemical processing, with the average particulate carbon oxidation state increasingly growing throughout the addressed exposure range (equivalent to 0.2 to 7 d in the atmosphere) with a ΔH:C/ΔO:C slope of −0.54. Simultaneously, the near-UV wavelength absorption by the particles increased due to enhanced particulate mass. The imaginary refractory indices of organic particulate matter were 0.0071 and 0.00013 at the wavelength of 520 nm for the fresh and photochemically processed particles, respectively, indicating secondary production of weakly absorbing brown carbon. The direct radiative forcing by the exhaust particles was estimated by a Mie model, which revealed a prominent shift from a warming to cooling climate effect upon photochemical aging. The results highlight the importance of considering secondary aerosol formation when assessing the environmental impacts of aviation.
Authors: Anni Hartikainen, Mika Ihalainen, Deeksha Shukla, Marius Rohkamp, Arya Mukherjee, Quanfu He, Sandra Piel, Aki Virkkula, Delun Li, Tuukka Kokkola, Seongho Jeong, Hanna Koponen, Uwe Etzien, Anusmita Das, Krista Luoma, Lukas Schwalb, Thomas Gröger, Alexandre Barth, Martin Sklorz, Thorsten Streibel, Hendryk Czech, Benedikt Gündling, Markus Kalberer, Bert Buchholz, Andreas Hupfer, Thomas Adam, Thorsten Hohaus, Johan Øvrevik, Ralf Zimmermann, Olli Sippula
Institutions: University of Eastern Finland, Helmholtz Munich, University of Rostock, Universität der Bundeswehr München, Forschungszentrum Jülich, Finnish Meteorological Institute, Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR), University of Basel, Norwegian Institute of Public Health, University of Oslo
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDG: Climate action
Open Access status: gold
Estimated APC paid: $1,725
OpenAlex ID: W4413703030