Impact of Aircraft Emissions on Ultrafine Particles Sulfate Content around Frankfurt/Main international Airport

Numerous studies have been reported that airport is an important source of ultrafine particles (UFPs, Dp ≤ 100 nm), potentially affecting the health of nearby residents. This study measured UFPs at the Frankfurt/Main international airport as well as in three locations (Raunheim, Schwanheim and Riedberg) at about 5 to 15 km from the airport. Cascade impactors (NanoMOUDI, TSI Inc.) collected UFPs in the size fractions of 56-100, 32-56, 18-32, and 10-18 nm on aluminum substrates during different seasons, allowing the observation of ground-level transport of UFPs. Before the campaign, three models of nanoMOUDI used in this study were collocated at the Goethe University (Riedberg campus) to compare data consistency. Inorganic ions, in particular sulfate, were then analyzed to determine the contribution of sulfur dioxide and sulfuric acid nucleation to the UFP mass concentration. Preliminary results indicate that the sampling efficiencies at UFP stages differed between the three applied impactor models and correction factors might need to be applied for more accurate concentration comparison. The measurements at the Frankfurt/Main international airport during Autumn 2023 showed highest concentrations of sulphate in the 32-56 nm size range, at approximately 40 ng m^-3, followed by 56-100 nm, 18-32 nm at ~18 and ~8 ng m^-3, respectively, and the lowest concentration was in the 10-18 nm range at ~2 ng m^-3. In the measurement campaigns in 2024, the preliminary results show mostly lower average sulfate concentrations in the UFP range at the sites more distant from the airport, ranging from ~ 2 ng m^-3 to ~20 ng m^-3. Similar relative variations across the UFP size range were observed at the two sites of Raunheim (mostly upwind of the airport) and Riedberg (~ 15 km away from the airport). The highest sulfate concentrations were found in the size range of 56-100 nm and the lowest concentration in the size range of 10-18 nm in both locations. The lowest sulfate concentration was also observed in the 10-18 nm size range in the samples collected at Schwanheim, the sampling site located closer and mostly downwind of the airport. However, the peak sulfate concentration was found in the size range of 32-56 nm, more similar to the relative profile observed directly on the airport. Next to emissions from aircraft engines, the difference in the peak concentration of sulfate may be influenced by several other factors, such as wind direction or other local emissions in the sampling sites. Detailed comparisons of UFP sulfate concentrations together with considerations of local meteorological conditions during the sampling periods will be presented in this contribution.