title: Rapid cycling of reactive nitrogen in the marine boundary layer.
abstract: Nitrogen oxides are essential for the formation of secondary atmospheric aerosols and of atmospheric oxidants such as ozone and the hydroxyl radical, which controls the self-cleansing capacity of the atmosphere. Nitric acid, a major oxidation product of nitrogen oxides, has traditionally been considered to be a permanent sink of nitrogen oxides. However, model studies predict higher ratios of nitric acid to nitrogen oxides in the troposphere than are observed. A 'renoxification' process that recycles nitric acid into nitrogen oxides has been proposed to reconcile observations with model studies, but the mechanisms responsible for this process remain uncertain. Here we present data from an aircraft measurement campaign over the North Atlantic Ocean and find evidence for rapid recycling of nitric acid to nitrous acid and nitrogen oxides in the clean marine boundary layer via particulate nitrate photolysis. Laboratory experiments further demonstrate the photolysis of particulate nitrate collected on filters at a rate more than two orders of magnitude greater than that of gaseous nitric acid, with nitrous acid as the main product. Box model calculations based on the Master Chemical Mechanism suggest that particulate nitrate photolysis mainly sustains the observed levels of nitrous acid and nitrogen oxides at midday under typical marine boundary layer conditions. Given that oceans account for more than 70 per cent of Earth's surface, we propose that particulate nitrate photolysis could be a substantial tropospheric nitrogen oxide source. Recycling of nitrogen oxides in remote oceanic regions with minimal direct nitrogen oxide emissions could increase the formation of tropospheric oxidants and secondary atmospheric aerosols on a global scale.
authors.affiliation: Wadsworth Center, New York State Department of Health, Albany, New York, USA.
authors.forename: Chunxiang
authors.initials: C
authors.lastname: Ye
authors.affiliation: Wadsworth Center, New York State Department of Health, Albany, New York, USA.|Department of Environmental Health Sciences, State University of New York, Albany, New York, USA.
authors.forename: Xianliang
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Department of Environmental Health Sciences, State University of New York, Albany, New York, USA.
authors.forename: Dennis
authors.initials: D
authors.lastname: Pu
authors.affiliation: Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles (UCLA), California, USA.
authors.forename: Jochen
authors.initials: J
authors.lastname: Stutz
authors.affiliation: Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles (UCLA), California, USA.
authors.forename: James
authors.initials: J
authors.lastname: Festa
authors.affiliation: Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles (UCLA), California, USA.
authors.forename: Max
authors.initials: M
authors.lastname: Spolaor
authors.affiliation: Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles (UCLA), California, USA.
authors.forename: Catalina
authors.initials: C
authors.lastname: Tsai
authors.affiliation: Department of Atmospheric and Oceanic Sciences, University of Colorado at Boulder, Boulder, Colorado, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Cantrell
authors.affiliation: Department of Atmospheric and Oceanic Sciences, University of Colorado at Boulder, Boulder, Colorado, USA.|Department of Physics, University of Helsinki, Helsinki, Finland.
authors.forename: Roy L
authors.initials: RL
authors.lastname: Mauldin
authors.affiliation: National Center for Atmospheric Research, Boulder, Colorado, USA.
authors.forename: Teresa
authors.initials: T
authors.lastname: Campos
authors.affiliation: National Center for Atmospheric Research, Boulder, Colorado, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Weinheimer
authors.affiliation: National Center for Atmospheric Research, Boulder, Colorado, USA.
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Hornbrook
authors.affiliation: National Center for Atmospheric Research, Boulder, Colorado, USA.
authors.forename: Eric C
authors.initials: EC
authors.lastname: Apel
authors.affiliation: Pacific Northwest National Laboratory, Richland, Washington, USA.
authors.forename: Alex
authors.initials: A
authors.lastname: Guenther
authors.affiliation: National Center for Atmospheric Research, Boulder, Colorado, USA.
authors.forename: Lisa
authors.initials: L
authors.lastname: Kaser
authors.affiliation: NOAA, Earth System Research Laboratory, Chemical Sciences Division, Boulder, Colorado, USA.|Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, Colorado, USA.
authors.forename: Bin
authors.initials: B
authors.lastname: Yuan
authors.affiliation: Institute for Meteorology and Geophysics, University of Innsbruck, Innsbruck, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Karl
authors.affiliation: National Center for Atmospheric Research, Boulder, Colorado, USA.
authors.forename: Julie
authors.initials: J
authors.lastname: Haggerty
authors.affiliation: National Center for Atmospheric Research, Boulder, Colorado, USA.
authors.forename: Samuel
authors.initials: S
authors.lastname: Hall
authors.affiliation: National Center for Atmospheric Research, Boulder, Colorado, USA.
authors.forename: Kirk
authors.initials: K
authors.lastname: Ullmann
authors.affiliation: National Center for Atmospheric Research, Boulder, Colorado, USA.|University of Eastern Finland, Kuopio, Finland.
authors.forename: James N
authors.initials: JN
authors.lastname: Smith
authors.affiliation: National Center for Atmospheric Research, Boulder, Colorado, USA.
authors.forename: John
authors.initials: J
authors.lastname: Ortega
authors.affiliation: National Center for Atmospheric Research, Boulder, Colorado, USA.
authors.forename: Christoph
authors.initials: C
authors.lastname: Knote
mesh_terms: D000336:Aerosols / Q000737:chemistry; D001267:Atlantic Ocean; D001272:Atmosphere / Q000737:chemistry*; D009566:Nitrates / Q000032:analysis / Q000737:chemistry; D017942:Nitric Acid / Q000737:chemistry; D009584:Nitrogen / Q000032:analysis* / Q000737:chemistry*; D009589:Nitrogen Oxides / Q000032:analysis* / Q000737:chemistry*; D009608:Nitrous Acid / Q000032:analysis / Q000737:chemistry; D009657:North Carolina; D016877:Oxidants / Q000737:chemistry; D010782:Photolysis; D012623:Seawater / Q000737:chemistry*; D013022:South Carolina
chemical_list: D000336:Aerosols; D009566:Nitrates; D009589:Nitrogen Oxides; D016877:Oxidants; D017942:Nitric Acid; D009584:Nitrogen; D009608:Nitrous Acid