Aviation and marine transport are globally important sources of carbonaceous aerosols into atmosphere, which likely cause substantial health and climate effects. Particle emissions from aviation and ships are not regulated by legislation as strictly as road traffic, and there are still large uncertainties in assessing their contribution to ambient aerosols. Particularly, the potential of the exhaust emissions of aviation and ships to generate secondary aerosols in the atmosphere and their chemical and optical properties are still poorly understood.
Laboratory experiments were carried out to simulate aviation and ship emissions and their atmospheric transformation. Aviation-like exhaust emissions were generated using a small jet engine burner operated with kerosine jet fuel. The selected operating condition was adjusted to mimic land and take-off cycle of a real aircraft. Ship emissions were generated using a single cylinder research marine engine operated with marine gas oil and heavy fuel oil according to the test cycle E2 of ISO 8178-4. The atmospheric aging of the exhaust emissions was simulated using the PEAR photochemical flow reactor (Ihalainen et al., 2019). Both fresh and aged aerosols were characterized with extensive online instrumentation. An aerosol mass spectrometer (AMS) and a proton-transfer-reaction mass spectrometer (PTR-MS) were used for chemical analysis of the exhaust particles and organic gases, respectively. Lightabsorbing particle components (i.e. black carbon and brown carbon) were measured using the 7-λ aethalometer, the photoacoustic extinctiometer (PAX) and lased induced incandescence (LII). Scanning mobility particle sizers (SMPS) were used to determine particle size distributions. Offline analyses of particle composition and optical properties were carried out with thermal-optical carbon analysis and UV-vis spectroscopy.
Photochemical aging of the jet engine exhaust led to a high secondary organic aerosol formation, with an increase of particulate mass by a factor of ~300. This also caused a significant increase in the light absorption by organic matter at lower visible wavelength, indicating aviation-derived exhaust as a potential important source of brown carbon in the atmosphere. For marine engine emissions, both the formation of secondary organic and inorganic aerosols were measured. Whereas, no obvious brown carbon formation was detected, the photochemical aging led to changes in black carbon mass absorption coefficients at visible wavelengths.
Literature:
[1] Ihalainen et al. (2019) Aerosol Science and Technology 53, 276-294.