Ultrasensitive Single-Particle Hygroscopic Growth Measurements of Regional Airport Aerosols

Aircraft exhaust creates intense, localized pollutant plumes near airports, and the emitted particles undergo rapid postemission aging and exert both direct and indirect climate effects. Their climatic influence hinges on how individual particles swell with ambient relative humidity (RH). Here, we deploy an ultrasensitive, label-free black-field microscopy technique enhanced by cascaded polarization filters in momentum space and quantify the hygroscopic growth of single-aerosol particles at multiple sites inside Hefei Xinqiao International Airport. Particles with equivalent optical diameters of approximately 80-400 nm are analyzed. Boarding bridge aerosols exhibit markedly lower equivalent optical growth factors (GFs) than those collected at other locations, and particles with different equivalent optical GFs exhibit different dry particle size distribution ranges across all locations. Coupled scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) analyses reveal that the carbon content of the aerosols is significantly elevated near the boarding bridges while elemental composition varies with particle size throughout the airport. The observed compositional variations account for the observed spatial and size-dependent hygroscopicity, demonstrate the applicability of the proposed single-particle optical technique in complex ambient environments, and underscore the need for microscale aerosol monitoring to accurately assess aviation impacts on regional radiation, cloud formation, and climate.