Physicochemical characterization of submicron particles using advanced drone-based systems: real-time measurements...

This study investigated the physicochemical properties of submicron atmospheric particles using an advanced drone-based system integrating a miniaturized real-time concentration measurement module and a surface-enhanced Raman spectroscopy-based single-particle analysis platform. This system enables vertical profiling of particle size distributions down to 20 nm and chemical characterization of submicron particle mixing states at ground level and aloft, capabilities beyond conventional Raman microspectrometry. Field campaigns were conducted in urban (Incheon) and semi-urban (Dangjin) environments to examine how aerosol composition and mixing states vary with altitude and location. In Incheon, although total submicron particle number concentrations were similar on the low- and high-pollution days, the latter exhibited a higher proportion of larger particles, resulting in elevated mass concentrations and degraded air quality. Internally mixed particles comprised 75.8 % at ground level and 54.5 % aloft, with nitrate-containing particles increasing from 36.2 % to 67.4 % at ground level and from 31.4 % to 77.2 % aloft under stagnant conditions. In Dangjin, high relative humidity (∼80 %) promoted secondary organic aerosol (SOA) formation and increased mixing complexity. On the more humid day, the SOA-containing particle fraction rose to 51.2 % at ground level and 29.2 % aloft, compared to ∼13 % on the less humid day. These results demonstrate that meteorological conditions, particularly humidity and atmospheric stability, critically influence particle composition and transformation. The integrated measurement system and resulting observations provide a representative picture of submicron aerosol behavior under real-world conditions, highlighting the robustness and potential of this approach for vertical aerosol characterization.