[Demarcke2010] "History effect of light and temperature on monoterpenoid emissions from Fagus sylvatica L.",
, vol. 44, no. 27: Elsevier, pp. 3261–3268, 2010.
Monoterpenoid emissions from Fagus sylvatica L. trees have been measured at light- and temperature-controlled conditions in a growth chamber, using Proton Transfer Reaction Mass Spectrometry (PTR-MS) and the dynamic branch enclosure technique. De novo synthesized monoterpenoid Standard Emission Factors, obtained by applying the G97 algorithm (Guenther, 1997), varied between 2 and 32 μg gDW−1 h−1 and showed a strong decline in late August and September, probably due to senescence. The response of monoterpenoid emissions to temperature variations at a constant daily light pattern could be well reproduced with a modified version of the MEGAN algorithm (Guenther et al., 2006), with a typical dependence on the average temperature over the past five days. The diurnal emissions at constant temperature showed a typical hysteretic behaviour, which could also be adequately described with the modified MEGAN algorithm by taking into account a dependence on the average light levels experienced by the trees during the past 10–13 h. The impact of the past light and temperature conditions on the monoterpenoid emissions from F. sylvatica L. was found to be much stronger than assumed in previous algorithms. Since our experiments were conducted under low light intensity, future studies should aim at confirming and completing the proposed algorithm updates in sunny conditions and natural environments.
[Demarcke2010a] "Laboratory studies in support of the detection of biogenic unsaturated alcohols by proton transfer reaction-mass spectrometry",
International Journal of Mass Spectrometry
, vol. 290, no. 1: Elsevier, pp. 14–21, 2010.
The effect of the ratio of the electric field to the buffer gas number density (E/N) in the drift tube reactor of a proton transfer reaction-mass spectrometer (PTR-MS) on the product ion distributions of seven common biogenic unsaturated alcohols (2-methyl-3-buten-2-ol, 1-penten-3-ol, cis-3-hexen-1-ol, trans-2-hexen-1-ol, 1-octen-3-ol, 6-methyl-5-hepten-2-ol and linalool) has been investigated. At low E/N values, the dominant product ion is the dehydrated protonated alcohol. Increasing E/N results in more extensive fragmentation for all compounds. For cis-3-hexenol and 6-methyl-5-hepten-2-ol the contribution of the protonated molecule can be enhanced by reducing E/N with respect to commonly used PTR-MS E/N values (120–130 Td). Significant differences have been found between some of the isomeric species studied, opening a way for selective detection. The C10 alcohol linalool mainly results in product ions at m/z 137 and 81, which are also PTR-MS fingerprints of monoterpenes. This may complicate monoterpene quantification when linalool and monoterpenes are simultaneously present in sampled air. Furthermore the influence of the water vapour pressure in the PTR-MS inlet line on the product ion distributions has been determined. Some major fingerprint ions of the unsaturated alcohols were found to depend significantly on the water vapour pressure in the inlet line and this should be taken into account for accurate quantification of these species by PTR-MS.
[Joo2010a] "Quantification of interferences in PTR-MS measurements of monoterpene emissions from Fagus sylvatica L. using simultaneous TD-GC-MS measurements",
International Journal of Mass Spectrometry
, vol. 291, no. 1: Elsevier, pp. 90–95, 2010.
The interest in quantitative analysis of biogenic volatile organic compounds (BVOCs) emissions stems from their importance in atmospheric chemistry. In order to compare the most frequently used BVOC measurement techniques, simultaneous on-line PTR-MS and off-line GC-MS data collection was performed on a 3 years old Fagus sylvatica L. tree placed in a growth chamber. Using an internal standard (deuterated toluene) and applying the selective ion mode (SIM) resulted in significant improvements of monoterpene (MT) quantification by TD-GC-MS. PTR-MS quantification of MTs was based on the ion signal at m/z 137. In the course of the experiments the relative contribution of linalool compared to that of MTs was found to be up to 84%. Since this compound has also a PTR-MS signature at m/z 137, quantification of MT emission rates by PTR-MS was disturbed. Comparison of GC-MS and PTR-MS data allowed an estimation of the ratio of the PTR-MS sensitivity for linalool to the one for MTs at m/z 137. This ratio of sensitivities, combined with the information of the relative contribution of linalool to the sum of linalool and MTs obtained by GC-MS, resulted in accurate derivation of the sum of emission rates of linalool and MTs by PTR-MS. The results indicate that fast and on-line PTR-MS measurements of BVOCs are best accompanied by off-line GC measurements to detect possible interferences or to use the additional information for properly quantifying the sum of emission rates of several compounds.
[Joo2010] "Variation in biogenic volatile organic compound emission pattern of Fagus sylvatica L. due to aphid infection",
, vol. 44, no. 2: Elsevier, pp. 227–234, 2010.
Volatile organic compounds (VOCs) have been the focus of interest to understand atmospheric processes and their consequences in formation of ozone or aerosol particles; therefore, VOCs contribute to climate change. In this study, biogenic VOCs (BVOCs) emitted from Fagus sylvatica L. trees were measured in a dynamic enclosure system. In total 18 compounds were identified: 11 monoterpenes (MT), an oxygenated MT, a homoterpene (C14H18), 3 sesquiterpenes (SQT), isoprene and methyl salicylate. The frequency distribution of the compounds was tested to determine a relation with the presence of the aphid Phyllaphis fagi L. It was found that linalool, (E)-β-ocimene, α-farnesene and a homoterpene identified as (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), were present in significantly more samples when infection was present on the trees. The observed emission spectrum from F. sylvatica L. shifted from MT to linalool, α-farnesene, (E)-β-ocimene and DMNT due to the aphid infection. Sabinene was quantitatively the most prevalent compound in both, non-infected and infected samples. In the presence of aphids α-farnesene and linalool became the second and third most important BVOC emitted. According to our investigation, the emission fingerprint is expected to be more complex than commonly presumed.