A drone-based sampling platform for vertically resolved chemical characterization of aerosol particles using chemical ionization mass spectrometry

Abstract. Aerosol concentrations and chemical composition exhibit strong spatial variability within the planetary boundary layer (PBL), driven by dynamic mixing, vertical development, and removal processes. Yet, vertically resolved measurements of particle-phase composition remain scarce. Here we present a drone-based platform for filter sampling of aerosol particles within the PBL, coupled with real-time meteorological sensing (temperature, relative humidity, wind speed and direction). This approach enhances spatial flexibility for targeted particle collection while enabling subsequent semi-online/offline chemical analysis with a chemical ionization time-of-flight mass spectrometer with a Filter Inlet for Gases and AEROsols (FIGAERO-CIMS). We deployed the platform at an urban site, where its meteorological sensors were validated against tower-based measurements and its particle sampling efficiency was benchmarked against a ground-based filter sampler. The sampling efficiency of the drone-based setup is demonstrated to be sufficient even under relatively clean atmospheric conditions (PM_2.5 ~2 µg m^-3), and is consistent with ground-based sampling with negligible interference from flight operations on collection. In addition, the thermal desorption profiles of individual species with the FIGAERO inlet, which offers a direct measurement of the volatility, exhibit high consistency between the drone-based and ground-based setups. Finally, we demonstrate its capability to resolve vertical gradients in aerosol molecular composition during PBL evolution. This study highlights the potential of unmanned aerial vehicle (UAV) based filter sampling to extend the spatial reach of aerosol chemical characterization using advanced mass spectrometry, providing a versatile tool to understand boundary layer dynamics and aerosol formation and evolution.