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

Understanding how aerosol chemical composition varies with height in the planetary boundary layer (PBL) is essential for interpreting aerosol sources, transformation pathways, and removal processes. Yet, observational constraints on vertically resolved particle-phase molecular composition are still limited, largely due to the lack of flexible sampling approaches. In this study, we introduce an unmanned aerial vehicle (UAV)–based aerosol filter sampling system that enables altitude-resolved particle collection within the PBL, accompanied by in situ measurements of key meteorological parameters, including temperature, relative humidity, and wind speed and direction. Collected aerosol samples are analysed using a chemical ionization time-of-flight mass spectrometer equipped with a Filter Inlet for Gases and AEROsols (FIGAERO-CIMS), allowing detailed characterization of particle-phase molecular composition and volatility.

The platform was tested during an urban deployment, where UAV-based meteorological observations were cross-validated against tower measurements, and aerosol collection performance was assessed through comparison with a co-located ground-based filter sampler. Despite low ambient particle mass loadings (PM₂.₅ ≈ 2 µg m⁻³), the UAV system achieved reliable particle collection, with sampling efficiencies comparable to ground-based measurements and no observable artefacts associated with flight operation. Consistent thermal desorption behaviour between airborne and ground-based samples further demonstrates the robustness of the approach.

We present first results revealing vertical gradients in aerosol molecular composition during PBL evolution, with a particular focus on night-time conditions. Observed compositional differences between altitudes highlight the influence of nocturnal stratification and limited mixing on aerosol chemical structure. Overall, this UAV-based filter sampling strategy expands the observational capability for aerosol chemical measurements and provides a new avenue for investigating PBL dynamics and aerosol processing in the lower atmosphere.