Communication Dans Un Congrès Année : 2025

Humidity driven spontaneous OH radical-initiated oxidation of pure organic aerosols

Résumé

The air-water interface of small particles exhibits high reactivity that can promote reactions which are thermodynamically unfavored in the bulk. There is many evidence that OH radicals can be spontaneously formed near the air–water interface of aqueous droplets. OH– anion has been suggested to partially exist as a radical-ion pair (OH...e-), which may undergo charge separation if subjected to an electric field, as the one existing at the air-water interface. In presence of organic molecules, the spontaneously generated OH radicals can lead to their oxidation hereby altering the composition of the particles. In this work we investigated the spontaneous oxidation of pure organic aerosols in the presence of water vapors and in the absence of any OH radical precursor or light. Dry organic particles were introduced into a flow tube reactor where they interacted with water vapors. The humidity level varied between 0 and 100 % RH. The chemical characterization of the particles was performed via offline measurements after particles collection onto filters, employing Liquid Chromatography coupled with Electrospray Ionization Orbitrap Mass Spectrometry. Online measurements were also performed using a VOCUS-AIM mass spectrometer. Finally, the effect of the particle size in the formation yields of the products was also investigated by performing size-resolved measurements. All the experiments provide evidence that organic droplets are oxidized while interacting with humidity. No products were observed under dry conditions. Oxidation products formation displayed a systematic increase with the increase of the RH denoting the enhancement of OH radical generation at the air-water interface. The size resolved measurements showed that smaller particles led to higher formation yields; high surface-to-volume ratio increases the reactivity. These results are expected to significantly improve our insights on the impact of interfacial processes on the atmospheric multiphase oxidation chemistry.

Fichier non déposé

Dates et versions

hal-05022664 , version 1 (07-04-2025)

Identifiants

  • HAL Id : hal-05022664 , version 1

Citer

M. Angelaki, M. Riva, J. Donalson, C. George. Humidity driven spontaneous OH radical-initiated oxidation of pure organic aerosols. Chemistry of Clouds Conference, Apr 2025, Sønderborg, Denmark. ⟨hal-05022664⟩
68 Consultations
0 Téléchargements

Partager

  • More