Deposition fluxes of terpenes over grassland

Abstract

[1] 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 reemission, 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., 1 April to 1 November 2009), 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 nonmethane 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.

Estimations of isoprenoid emission capacity from enclosure studies: measurements, data processing, quality and standardized measurement protocols

“…In contrast, use of ambient air can even result in reversal of the flux direction in the case of strong deposition velocities, especially for compounds with high potential deposition rate such as highly lipid-soluble terpenoids and highly water-soluble oxygenated compounds (Bamberger et al, 2011;Karl et al, 2005;Noe et al, 2008). However, as shown above, in reality, this is only a potential problem in species with low emission rates that can build up only a low chamber BVOC concentration close to or below typical ambient concentrations.…”

“…While fast BVOC sensors for online measurements such as chemiluminescence 2220Ü. Niinemets et al: Estimations of isoprenoid emission capacity from enclosure studies detection for isoprene (Hills and Zimmerman, 1990) and proton transfer reaction mass-spectrometry (PTR-MS) for methylbutenol, isoprene, and total mono-and sesquiterpenes (Lindinger et al, 1998a, b) are available, and higher mass resolution techniques such as time-of-flight (TOF) massspectrometry (PTR-TOF-MS, Bamberger et al, 2011;Cappellina et al, 2010) are becoming available, quantitative and qualitative separation of mono-and sesquiterpene species with the same molecular mass requires gas-chromatographic separation, for which samples need to be concentrated. Gaschromatographic analysis is also recommended to avoid artifacts in isoprenoid emission measurements by PTR-MS due to protonated parent ions or fragment ions with the same m/z as the isoprenoid studied.…”

Plant surface reactions: an opportunistic ozone defence mechanism impacting atmospheric chemistry

“…Resins can be released during mechanical stress, e.g. in the event of hail storms (Bamberger et al, 2011) and could eventually evaporate depending on their vapour pressure (and therefore ambient temperature).…”

Boreal forest BVOC exchange: emissions versus in-canopy sinks

“…Karl et al (2010) observed substantial dry deposition removal of several OVOCs in field measurements. Bamberger et al (2011) observed the deposition fluxes of monoterpenes, sesquiterpenes, and oxygenated terpenes over a temperate mountain grassland in an alpine valley after a hailstorm. Park et al (2013) directly observed bidirectional fluxes for 494 organic ions and daily mean net deposition for 186 organic ions over an orange grove, and recently Nguyen et al (2015) observed dominant daytime dry deposition fluxes for small, saturated OVOCs derived from isoprene and monoterpene oxidation during summer.…”