Abstract. Civil aviation is undergoing rapid growth as a result of global economic development. Characterizing ultrafine particle emissions from jet aircraft equipped with turbofan engines, which are commonly used in civil aviation, is an important issue for the assessment of the impacts of aviation on climate and on human health. Previous studies have reported that particle number emissions from jet aircraft are dominated by volatile particles (mainly sulphate and organics) with mode diameters of 10–20 nm and that non-volatile particles (mainly soot) exhibit mode diameters of ~20–60 nm, depending on the engine types and thrust conditions. However, there are significant uncertainties in measuring particles with diameters smaller than ~10 nm, especially when fresh aircraft exhaust plumes are measured near the emission sources. We conducted field observations of aerosols and carbon dioxide (CO2) near a runway of Narita International Airport, Japan, in February 2018, with specific focuses on the contributions of sub-10 nm size ranges to total and non-volatile particles. Spiked increases in particle number concentrations and CO2 were observed to be associated with wind directions from the runway, which can be attributed to diluted aircraft exhaust plumes. We estimated the particle number emission indices (EIs) for discrete take-off plumes. The median total particle number EI with diameters larger than 2.5 nm was ~60 times greater than the median non-volatile particle number EI with diameters larger than 10 nm for take-off plumes. This value can be interpreted as the difference between total particle number emissions under real-world conditions and non-volatile particle number emissions regulated by standard engine tests. More than half of particle numbers in the plumes were found in the size range smaller than ~10 nm on average for both total and non-volatile particles. The mode diameters of the size distributions of particle number EIs were found to be smaller than ~10 nm in most cases, and the peak EI values were larger than those previously reported under real-world operating conditions. This study provides new insights into the significance of sub-10 nm particles in aircraft exhaust plumes under real-world conditions, which is important in understanding aviation impacts on human health and also in developing aviation emission inventories for regional and global models.
Non-volatile particle emissions from aircraft turbine engines at ground-idle induce oxidative stress in bronchial cells