The High Pressure Inside Aerosol Particles Enhances Photochemical Reactions of Biomass Burning Compounds

• Published in: ACS earth and space chemistry Vol. 8; no. 5; pp. 1062 - 1071
• Main Authors: Dubois, Clément, Perrier, Sébastien, George, Christian, Riva, Matthieu
• Format: Journal Article
• Language: English
• Published: American Chemical Society 16.05.2024; ACS
• Subjects: Catalysis; Chemical Sciences; Environment and Society; Environmental Sciences; atmosphere; radical reactions; biomass burning; aerosols; Laplace pressure; chemical reactions
• ISSN: 2472-3452; 2472-3452
• DOI: 10.1021/acsearthspacechem.4c00011

Ultrafine aerosols (d < 100 nm) are the most abundant particles in the atmosphere with strong implications for climate and air quality. Their formation and evolution remain a subject of significant uncertainty. Recently, the implication of a fundamental and hitherto unconsidered characteristic of ultrafine aerosols has been highlighted: the Young–Laplace pressure. Here, the photochemical reaction of vanillin, a proxy for biomass burning compounds, under various high pressures was investigated. Using high-resolution mass spectrometry and UV–visible spectroscopy, we demonstrated that vanillin photodegradation was faster by ∼40% under high pressures typical of atmospheric nanoparticles. Chemical characterization shows that dimer formation, ring-opening, and cleavage processes were greatly favored (i.e., up to ∼250%) at high pressures. While the formation of light-absorbing compounds appears to be nonaffected, their decomposition through photooxidative processes was shown to be 50% faster at high pressures. This study establishes that the high pressure inside nanometric-sized aerosols has to be considered as a key property that can significantly impact photochemical processes involved in aerosol growth and aging.