This study investigates the atmospheric chemistry of Myrtenal, a first-generation terpene oxidation product from α-pinene. Using an acoustic levitation system coupled with Raman microspectroscopy, we tracked the chemical composition and morphology changes of Myrtenal droplets exposed to ambient humidity. At high relative humidity (80%), rapid chemical transformation occurred, suggesting water's role in the reaction, with slower transformations at lower humidity. Bulk experiments confirmed similar transformations, with faster reactions at the particle scale. These findings reveal oligomerization of Myrtenal rather than microsolvation and emphasize the importance of particle surfaces in facilitating these reactions.

The partitioning of organic aerosol components between gas and aqueous phases depends on Henry’s law constants, yet experimental constraints remain limited. We present a novel method that combines volatility-based fractionation with aqueous solubility measurements to determine their distribution. Applied to SOA from the a-pinene ozonolysis, this approach estimates Henry’s law constants within the Volatility Basis Set framework. Most SOA components with C* in the 10–100 µg m⁻³ range exhibit moderate to slow deposition, while only lower limits are determined for the most volatile SOA (C* = 1000 µg m⁻³). These results enhance SOA removal processes in chemical transport models.

Aerosols originate from natural and anthropogenic sources, with sizes ranging from a few nanometers to a few micrometers. Aerosols significantly impact human health, climate and the ecosystem. The acidity of aerosols modulates nearly all of their properties and processes, yet it has remained virtually unconstrained for decades. The objective of this study is to design and test a non-invasive strategy for monitoring the pH of aerosols. The methodology is based on the deposition of aerosols on functionalized pH-sensitive filter surfaces that get protonated in acidic conditions resulting in structural variations that exhibit distinct Raman fingerprints which is monitored via Raman/SERS.

Aging processes of organic aerosol particles can significantly alter their physicochemical properties, such as viscosity and hygroscopicity, thereby affecting the Earth’s energy budget and climate. Currently, it is not known whether any synergistic effects exist between photolysis and ozonolysis. In this work, the water diffusivity and hygroscopicity of aqueous trans-aconitic acid particles are measured after aging using Electrodynamic Balance set-up. Preliminary results indicate two orders of magnitude increase in viscosity after aging with UV and ozone simultaneously and with UV alone up to 60% mass loss, followed by viscosity reduction upon further UV-aging. Hygroscopicity did not change significantly after aging.