title: Alternative pathway for atmospheric particles growth.
abstract: Credible climate change predictions require reliable fundamental scientific knowledge of the underlying processes. Despite extensive observational data accumulated to date, atmospheric aerosols still pose key uncertainties in the understanding of Earth's radiative balance due to direct interaction with radiation and because they modify clouds' properties. Specifically, major gaps exist in the understanding of the physicochemical pathways that lead to aerosol growth in the atmosphere and to changes in their properties while in the atmosphere. Traditionally, the driving forces for particle growth are attributed to condensation of low vapor pressure species following atmospheric oxidation of volatile compounds by gaseous oxidants. The current study presents experimental evidence of an unaccounted-for new photoinduced pathway for particle growth. We show that heterogeneous reactions activated by light can lead to fast uptake of noncondensable Volatile Organic Compounds (VOCs) at the surface of particles when only traces of a photosensitizer are present in the seed aerosol. Under such conditions, size and mass increase; changes in the chemical composition of the aerosol are also observed upon exposure to volatile organic compounds such as terpenes and near-UV irradiation. Experimentally determined growth rate values match field observations, suggesting that this photochemical process can provide a new, unaccounted-for pathway for atmospheric particle growth and should be considered by models.
authors.affiliation: Université de Lyon, Université Lyon 1, Centre National de la Recherche Scientifique, Unité Mixte de Recherche, 5256, IRCELYON, Institut de Recherches sur la Catalyse et l’Environnement de Lyon, F-69626 Villeurbanne, France.
authors.forename: Maria Eugenia
authors.initials: ME
authors.lastname: Monge
authors.forename: Thomas
authors.initials: T
authors.lastname: Rosenørn
authors.forename: Olivier
authors.initials: O
authors.lastname: Favez
authors.forename: Markus
authors.initials: M
authors.lastname: Müller
authors.forename: Gabriela
authors.initials: G
authors.lastname: Adler
authors.forename: Ali
authors.initials: A
authors.lastname: Abo Riziq
authors.forename: Yinon
authors.initials: Y
authors.lastname: Rudich
authors.forename: Hartmut
authors.initials: H
authors.lastname: Herrmann
authors.forename: Christian
authors.initials: C
authors.lastname: George
authors.forename: Barbara
authors.initials: B
authors.lastname: D'Anna