title: A large source of low-volatility secondary organic aerosol.
abstract: Forests emit large quantities of volatile organic compounds (VOCs) to the atmosphere. Their condensable oxidation products can form secondary organic aerosol, a significant and ubiquitous component of atmospheric aerosol, which is known to affect the Earth's radiation balance by scattering solar radiation and by acting as cloud condensation nuclei. The quantitative assessment of such climate effects remains hampered by a number of factors, including an incomplete understanding of how biogenic VOCs contribute to the formation of atmospheric secondary organic aerosol. The growth of newly formed particles from sizes of less than three nanometres up to the sizes of cloud condensation nuclei (about one hundred nanometres) in many continental ecosystems requires abundant, essentially non-volatile organic vapours, but the sources and compositions of such vapours remain unknown. Here we investigate the oxidation of VOCs, in particular the terpene α-pinene, under atmospherically relevant conditions in chamber experiments. We find that a direct pathway leads from several biogenic VOCs, such as monoterpenes, to the formation of large amounts of extremely low-volatility vapours. These vapours form at significant mass yield in the gas phase and condense irreversibly onto aerosol surfaces to produce secondary organic aerosol, helping to explain the discrepancy between the observed atmospheric burden of secondary organic aerosol and that reported by many model studies. We further demonstrate how these low-volatility vapours can enhance, or even dominate, the formation and growth of aerosol particles over forested regions, providing a missing link between biogenic VOCs and their conversion to aerosol particles. Our findings could help to improve assessments of biosphere-aerosol-climate feedback mechanisms, and the air quality and climate effects of biogenic emissions generally.
authors.affiliation: 1] Institute for Energy and Climate Research (IEK-8), Forschungszentrum Jülich, 52425 Jülich, Germany [2] Department of Physics, PO Box 64, 00014 University of Helsinki, Finland.
authors.forename: Mikael
authors.initials: M
authors.lastname: Ehn
authors.affiliation: 1] Department of Physics, PO Box 64, 00014 University of Helsinki, Finland [2] Department of Atmospheric Sciences, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Joel A
authors.initials: JA
authors.lastname: Thornton
authors.affiliation: Institute of Bio- and Geosciences (IBG-2), Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: Einhard
authors.initials: E
authors.lastname: Kleist
authors.affiliation: Department of Physics, PO Box 64, 00014 University of Helsinki, Finland.
authors.forename: Mikko
authors.initials: M
authors.lastname: Sipilä
authors.affiliation: Department of Physics, PO Box 64, 00014 University of Helsinki, Finland.
authors.forename: Heikki
authors.initials: H
authors.lastname: Junninen
authors.affiliation: Institute for Energy and Climate Research (IEK-8), Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: Iida
authors.initials: I
authors.lastname: Pullinen
authors.affiliation: Institute for Energy and Climate Research (IEK-8), Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: Monika
authors.initials: M
authors.lastname: Springer
authors.affiliation: Institute for Energy and Climate Research (IEK-8), Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Rubach
authors.affiliation: Institute for Energy and Climate Research (IEK-8), Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Tillmann
authors.affiliation: Department of Atmospheric Sciences, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Ben
authors.initials: B
authors.lastname: Lee
authors.affiliation: Department of Atmospheric Sciences, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Felipe
authors.initials: F
authors.lastname: Lopez-Hilfiker
authors.affiliation: Institute for Energy and Climate Research (IEK-8), Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Andres
authors.affiliation: Institute for Energy and Climate Research (IEK-8), Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: Ismail-Hakki
authors.initials: IH
authors.lastname: Acir
authors.affiliation: Department of Physics, PO Box 64, 00014 University of Helsinki, Finland.
authors.forename: Matti
authors.initials: M
authors.lastname: Rissanen
authors.affiliation: 1] Department of Physics, PO Box 64, 00014 University of Helsinki, Finland [2] Institute for Tropospheric Research (TROPOS), 04318 Leipzig, Germany.
authors.forename: Tuija
authors.initials: T
authors.lastname: Jokinen
authors.affiliation: Department of Physics, PO Box 64, 00014 University of Helsinki, Finland.
authors.forename: Siegfried
authors.initials: S
authors.lastname: Schobesberger
authors.affiliation: Department of Physics, PO Box 64, 00014 University of Helsinki, Finland.
authors.forename: Juha
authors.initials: J
authors.lastname: Kangasluoma
authors.affiliation: Department of Physics, PO Box 64, 00014 University of Helsinki, Finland.
authors.forename: Jenni
authors.initials: J
authors.lastname: Kontkanen
authors.affiliation: 1] Department of Physics, PO Box 64, 00014 University of Helsinki, Finland [2] Helsinki Institute of Physics, PO Box 64, 00014 University of Helsinki, Finland.
authors.forename: Tuomo
authors.initials: T
authors.lastname: Nieminen
authors.affiliation: Department of Chemistry, PO Box 55, 00014 University of Helsinki, Finland.
authors.forename: Theo
authors.initials: T
authors.lastname: Kurtén
authors.affiliation: Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark.
authors.forename: Lasse B
authors.initials: LB
authors.lastname: Nielsen
authors.affiliation: Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark.
authors.forename: Solvejg
authors.initials: S
authors.lastname: Jørgensen
authors.affiliation: Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark.
authors.forename: Henrik G
authors.initials: HG
authors.lastname: Kjaergaard
authors.affiliation: Aerodyne Research, Inc., 45 Manning Road, Billerica, Massachusetts 01821, USA.
authors.forename: Manjula
authors.initials: M
authors.lastname: Canagaratna
authors.affiliation: Department of Physics, Tampere University of Technology, PO Box 692, 33101 Tampere, Finland.
authors.forename: Miikka Dal
authors.initials: MD
authors.lastname: Maso
authors.affiliation: Institute for Tropospheric Research (TROPOS), 04318 Leipzig, Germany.
authors.forename: Torsten
authors.initials: T
authors.lastname: Berndt
authors.affiliation: Department of Physics, PO Box 64, 00014 University of Helsinki, Finland.
authors.forename: Tuukka
authors.initials: T
authors.lastname: Petäjä
authors.affiliation: Institute for Energy and Climate Research (IEK-8), Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Wahner
authors.affiliation: Department of Physics, PO Box 64, 00014 University of Helsinki, Finland.
authors.forename: Veli-Matti
authors.initials: VM
authors.lastname: Kerminen
authors.affiliation: Department of Physics, PO Box 64, 00014 University of Helsinki, Finland.
authors.forename: Markku
authors.initials: M
authors.lastname: Kulmala
authors.affiliation: 1] Department of Physics, PO Box 64, 00014 University of Helsinki, Finland [2] Aerodyne Research, Inc., 45 Manning Road, Billerica, Massachusetts 01821, USA.
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Worsnop
authors.affiliation: Institute of Bio- and Geosciences (IBG-2), Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Wildt
authors.affiliation: Institute for Energy and Climate Research (IEK-8), Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Mentel
mesh_terms: D000336:Aerosols / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D001272:Atmosphere / Q000737:chemistry; D000081008:Bicyclic Monoterpenes; D002980:Climate; D017753:Ecosystem; D005387:Finland; D005740:Gases / Q000032:analysis / Q000737:chemistry; D008956:Models, Chemical; D039821:Monoterpenes / Q000737:chemistry; D010084:Oxidation-Reduction; D010126:Ozone / Q000737:chemistry; D010316:Particle Size; D014197:Trees / Q000378:metabolism; D055549:Volatile Organic Compounds / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D014835:Volatilization
chemical_list: D000336:Aerosols; D000081008:Bicyclic Monoterpenes; D005740:Gases; D039821:Monoterpenes; D055549:Volatile Organic Compounds; D010126:Ozone; C005451:alpha-pinene