title: Deposition Fluxes of Terpenes over Grassland.
abstract: Eddy covariance flux measurements were carried out for two subsequent vegetation periods above a temperate mountain grassland in an alpine valley using a proton-transfer-reaction - mass spectrometer (PTR-MS) and a PTR-time of flight - mass spectrometer (PTR-TOF). In 2008 and during the first half of the vegetation period 2009 the volume mixing ratios (VMRs) for the sum of monoterpenes (MTs) were typically well below 1 ppbv and neither MT emission nor deposition was observed. After a hailstorm in July 2009 an order of magnitude higher amount of terpenes was transported to the site from nearby coniferous forests causing elevated VMRs. As a consequence, deposition fluxes of terpenes to the grassland, which continued over a time period of several weeks without significant re-emission, were observed. For days without precipitation the deposition occurred at velocities close to the aerodynamic limit. In addition to monoterpene uptake, deposition fluxes of the sum of sesquiterpenes (SQTs) and the sum of oxygenated terpenes (OTs) were detected. Considering an entire growing season for the grassland (i.e., 1stof April to 1stof November), the cumulative carbon deposition of monoterpenes reached 276 mg C m-2. This is comparable to the net carbon emission of methanol (329 mg C m-2), which is the dominant non methane volatile organic compound (VOC) emitted from this site, during the same time period. It is suggested that deposition of monoterpenes to terrestrial ecosystems could play a more significant role in the reactive carbon budget than previously assumed.
authors.affiliation: Institute of Ion Physics and Applied Physics, University of Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
authors.forename: I
authors.initials: I
authors.lastname: Bamberger
authors.affiliation: Institute of Ecology, University of Innsbruck, Sternwartestraße 15, 6020 Innsbruck, Austria.
authors.forename: L
authors.initials: L
authors.lastname: Hörtnagl
authors.affiliation: Institute of Ion Physics and Applied Physics, University of Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria ; Division of Atmospheric Sciences, Department of Physics, Gustaf Hällströmin katu 2, 00014 University of Helsinki, Finland.
authors.forename: T M
authors.initials: TM
authors.lastname: Ruuskanen
authors.affiliation: Institute of Ion Physics and Applied Physics, University of Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria ; Ionicon Analytik, Eduard-Bodem-Gasse 3, 6020 Innsbruck, Austria.
authors.forename: R
authors.initials: R
authors.lastname: Schnitzhofer
authors.affiliation: Institute of Ion Physics and Applied Physics, University of Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Müller
authors.affiliation: Institute of Ion Physics and Applied Physics, University of Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria ; Chemical Sciences Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80307, USA ; Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA.
authors.forename: M
authors.initials: M
authors.lastname: Graus
authors.affiliation: Institute of Ion Physics and Applied Physics, University of Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria ; NCAR Earth Systems Laboratory, National Center for Atmospheric Research, Boulder, CO 80301, USA.
authors.forename: T
authors.initials: T
authors.lastname: Karl
authors.affiliation: Institute of Ecology, University of Innsbruck, Sternwartestraße 15, 6020 Innsbruck, Austria.
authors.forename: G
authors.initials: G
authors.lastname: Wohlfahrt
authors.affiliation: Institute of Ion Physics and Applied Physics, University of Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
authors.forename: A
authors.initials: A
authors.lastname: Hansel