Detection of Plant Volatiles after Leaf Wounding and Darkening by Proton Transfer Reaction ‘‘Time-of-Flight’’ Mass Spectrometry (PTR-TOF)

Peer reviewe

Towards long-term standardised carbon and greenhouse gas observations for monitoring Europe's terrestrial ecosystems : a review

Research infrastructures play a key role in launching a new generation of integrated long-term, geographically distributed observation programmes designed to monitor climate change, better understand its impacts on global ecosystems, and evaluate possible mitigation and adaptation strategies. The pan-European Integrated Carbon Observation System combines carbon and greenhouse gas (GHG; CO2, CH4, N2O, H2O) observations within the atmosphere, terrestrial ecosystems and oceans. High-precision measurements are obtained using standardised methodologies, are centrally processed and openly available in a traceable and verifiable fashion in combination with detailed metadata. The Integrated Carbon Observation System ecosystem station network aims to sample climate and land-cover variability across Europe. In addition to GHG flux measurements, a large set of complementary data (including management practices, vegetation and soil characteristics) is collected to support the interpretation, spatial upscaling and modelling of observed ecosystem carbon and GHG dynamics. The applied sampling design was developed and formulated in protocols by the scientific community, representing a trade-off between an ideal dataset and practical feasibility. The use of open-access, high-quality and multi-level data products by different user communities is crucial for the Integrated Carbon Observation System in order to achieve its scientific potential and societal value.Peer reviewe

Qualitative and quantitative characterization of volatile organic compound emissions from cut grass

Mechanical wounding of plants triggers the release of a blend of reactive biogenic volatile organic compounds (BVOCs). During and after mowing and harvesting of managed grasslands, significant BVOC emissions have the potential to alter the physical and chemical properties of the atmosphere and lead to ozone and aerosol formation with consequences for regional air quality. We show that the amount and composition of BVOCs emitted per unit dry weight of plant material is comparable between laboratory enclosure measurements of artificially severed grassland plant species and in situ ecosystem-scale flux measurements above a temperate mountain grassland during and after periodic mowing and harvesting. The investigated grassland ecosystem emitted annually up to 130 mg carbon m(−2) in response to cutting and drying, the largest part being consistently represented by methanol and a blend of green leaf volatiles (GLV). In addition, we report the plant species-specific emission of furfural, terpenoid-like compounds (e.g. camphor), and sesquiterpenes from cut plant material, which may be used as tracers for the presence of given plant species in the ecosystem

Acetaldehyde exchange above a managed temperate mountain grassland

An overview of acetaldehyde exchange above a managed temperate mountain grassland in Austria over four growing seasons is presented. The meadow acted as a net source of acetaldehyde in all 4 years, emitting between 7 and 28 mgCm−2 over the whole growing period. The cutting of the meadow resulted in huge acetaldehyde emission bursts of up to 16.5 nmolm−2 s−1 on the day of harvesting or 1 day later. During undisturbed conditions both periods with net uptake and net emissions of acetaldehyde were observed. The bidirectional nature of acetaldehyde fluxes was also reflected by clear diurnal cycles during certain time periods, indicating strong deposition processes before the first cut and emission towards the end of the growing season. The analysis of acetaldehyde compensation points revealed a complex relationship between ambient acetaldehyde mixing ratios and respective fluxes, significantly influenced by multiple environmental parameters and variable throughout the year. As a major finding of this study, we identified both a positive and negative correlation between concentration and flux on a daily scale, where soil temperature and soil water content were the most significant factors in determining the direction of the slope. In turn, this bidirectional relationship on a daily scale resulted in compensation points between 0.40 and 0.54 ppbv, which could be well explained by collected ancillary data. We conclude that in order to model acetaldehyde fluxes at the site in Neustift on a daily scale over longer time periods, it is crucial to know the type of relationship, i.e., the direction of the slope, between mixing ratios and fluxes on a given day.ISSN:1680-7375ISSN:1680-736

Acetaldehyde exchange above a managed temperate mountain grassland

ISSN:1680-7375ISSN:1680-736

Dual-Stage Consumable-Free Thermal Modulator for the Hyphenation of Thermal Analysis, Gas Chromatography, and Mass Spectrometry

The design of the so-called “Peltier modulator” is presented. It is a new dual-stage consumable-free thermal modulator for thermal analysis-gas chromatography-mass spectrometry (TA-GC-MS). It requires only electrical power for operation as it facilitates thermo-electric coolers instead of cryogenics for trapping and resistive on-column heating for reinjection. Trapping and desorption temperatures as well as modulation cycles are freely adjustable. The stationary phase for the trapping region can be selected to suit the specific application, since common fused silica capillary is used. The Peltier modulator’s performance is demonstrated with a broad range of different standard substances and with heavy crude oil as a complex real life sample. Successful modulation from <i>n</i>-pentane to pyrene (boiling points = 36/394 °C) is presented. The produced peaks show the narrowest bandwidths ever reported for a consumable-free thermal modulator, i.e., 12.8 ± 1.2 ms for <i>n</i>-pentadecane. The Peltier modulator is rugged, cost-effective, requires low maintenance, and decreases security issues significantly, compared to commercial available solutions using liquid N₂/CO₂

Optically Heated Ultra-Fast-Cycling Gas Chromatography Module for Separation of Direct Sampling and Online Monitoring Applications

This work describes an ultrafast-cycling gas chromatography module (fast-GC module) for direct-sampling gas chromatography/mass spectrometry (GC-MS). The sample can be introduced into the fast-GC module using a common GC injector or any GC × GC modulator. The new fast-GC module offers the possibility to conduct a complete temperature cycle within 30 s. Its thermal mass is minimized by using a specially developed home-built fused silica capillary column stack and a halogen lamp for heat generation, both placed inside a gold-coated quartz glass cylinder. A high airflow blower enables rapid cooling. The new device is highly flexible concerning the used separation column, the applied temperature program, and the integration into existing systems. An application of the fast-GC module is shown in this work by thermal analysis coupled to gas chromatography-mass spectrometry (TA-GC-MS). The continuously evolving gases of the TA are modulated by a liquid CO₂ modulator. Because of the rapid cycling of the fast-GC module, it is possible to obtain the best separation while maintaining the online character of the TA. Restrictions in separation and retention time shifting, known from isothermal and normal ramped fast-GC systems, are overcome

Total amount (mass) of ions <i>m/z</i> = 81.070 [(<i>Z</i>)-3-hexenal+(<i>E</i>)-3-hexenal] (black circles) and <i>m/z</i> = 83.085 [(<i>Z</i>)-3-hexenol+(<i>E</i>)-3-hexenol+(<i>E</i>)-2-hexenol+hexanal] (open circles) as a function of cut lengths [mm] produced when wounding <i>Dactlylis glomerata</i> leaves (R² = 0.91 solid line; R² = 0.88 dotted line).

<p>Circles represent results from 7 experiments carried out on single leaves.</p

Time course of BVOC emission and gas exchange of intact <i>Dactlylis glomerata</i> (a, d, g), <i>Populus alba</i> (b, e, h) and <i>Quercus ilex</i> (c, f, i) leaves following rapid light-dark transitions.

<p>The light was switched off at the time indicated by the arrows. Different colors indicate different ions: (a, b, c) <i>m/z</i> = 81.070 [(<i>Z</i>)-3-hexenal+(<i>E</i>)-3-hexenal]; <i>m/z</i> = 83.085 [(<i>Z</i>)-3-hexenol+(<i>E</i>)-3-hexenol+(<i>E</i>)-2-hexenol+hexanal]; <i>m/z</i> = 43.018 [hexyl acetates]; m/z = 143.107 [(<i>Z</i>)-3-hexenyl acetate+(<i>E</i>)-2-hexenyl acetate]. (d, e, f) <i>m/z</i> = 33.034 [methanol]; <i>m/z</i> = 45.054 [acetaldehyde]; <i>m/z</i> = 69.070 [isoprene] (only in <i>P. alba -</i> panel e); <i>m/z</i> = 71.086 [pentenal fragment]; <i>m/z</i> = 137.133 [monoterpenes] (only in <i>Q. ilex -</i> panel f). (g, h, i) Photosynthetic carbon assimilation (black circles) and stomatal conductance (open circles). One typical sequence out of four independent experiments is shown.</p

Relationship between constitutive carbon emitted as isoprenoids (isoprene in <i>P. alba</i>; monoterpenes in <i>Q. ilex</i>) and the total amount of carbon emitted as acetaldehyde after fast transition from light to dark conditions (linear regression R² = 0.55).

<p>The emission measured in 3 different leaves of <i>P. alba</i> (black circles) and 4 different leaves of <i>Q. ilex</i> (white circles) are shown. Each leaf was selected from different individuals in both plant species.</p