| 1. |
- Esper, Jan, et al.
(author)
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Site-specific climatic signals in stable isotope records from Swedish pine forests
- 2018
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In: Trees. - : Springer Science and Business Media LLC. - 0931-1890 .- 1432-2285. ; 32:3, s. 855-869
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Journal article (peer-reviewed)abstract
- Pinus sylvestris tree-ring delta C-13 and delta O-18 records from locally moist sites in central and northern Sweden contain consistently stronger climate signals than their dry site counterparts. We produced twentieth century stable isotope data from Pinus sylvestris trees near lakeshores and inland sites in northern Sweden (near Kiruna) and central Sweden (near Stockholm) to evaluate the influence of changing microsite conditions on the climate sensitivity of tree-ring delta C-13 and delta O-18. The data reveal a latitudinal trend towards lower C and O isotope values near the Arctic tree line (-0.8 parts per thousand for delta C-13 and - 2.4 parts per thousand for delta O-18 relative to central Sweden) reflecting widely recognized atmospheric changes. At the microsite scale, delta C-13 decreases from the dry inland to the moist lakeshore sites (- 0.7 parts per thousand in Kiruna and - 1.2 parts per thousand in Stockholm), evidence of the importance of groundwater access to this proxy. While all isotope records from northern and central Sweden correlate significantly against temperature, precipitation, cloud cover and/or drought data, climate signals in the records from moist microsites are consistently stronger, which emphasizes the importance of site selection when producing stable isotope chronologies. Overall strongest correlations are found with summer temperature, except for delta O-18 from Stockholm correlating best with instrumental drought indices. These findings are complemented by significant positive correlations with temperature-sensitive ring width data in Kiruna, and inverse (or absent) correlations with precipitation-sensitive ring width data in Stockholm. A conclusive differentiation between leading and co-varying forcings is challenging based on only the calibration against often defective instrumental climate data, and would require an improved understanding of the physiological processes that control isotope fractionation at varying microsites and joined application of forward modelling.
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| 2. |
- Greule, Markus, et al.
(author)
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Improved rapid authentication of vanillin using δ13C and δ2H values
- 2010
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In: European Food Research and Technology. - : Springer Science and Business Media LLC. - 1438-2377 .- 1438-2385. ; 231:6, s. 933-941
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Journal article (peer-reviewed)abstract
- Vanilla still remains one of the most important and widely used flavours in the food industry and is also extensively employed by fragrance and pharmaceutical manufacturing companies. Natural vanilla flavour, extracted from the pods of the tropic orchid vanilla, is considerably more expensive than synthetic vanillin. The disparity of prices between natural vanillin and that derived from other sources has given rise to many cases of fraudulent adulteration, and for more than 30 years, strenuous efforts have been made to authenticate sources of vanillin. Stable isotope analysis is one of the most powerful analytical tools to distinguish between natural vanillin and that originating from other sources. Recently, a rapid and precise method for analysis of both δ13C and δ2H values of plant methoxyl groups has been published. Here, we report an application of the method for the control of authenticity of vanillin. Carbon and hydrogen stable isotope values of the vanillin molecule and vanillin methoxyl groups of vanillin samples of different origins including authentic and synthetic samples were measured. The results clearly show that use of this approach provides a rapid and reliable authenticity assessment of vanillin. The technique used for these studies is robust and rapid, involves minimum sample preparation and requires only a small amount of vanillin sample, usually 1 mg for stable carbon and 4 mg for stable hydrogen analysis.
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| 3. |
- Horst, Axel, et al.
(author)
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Stable bromine isotopic composition of methyl bromide released from plant matter
- 2014
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In: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 125, s. 186-195
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Journal article (peer-reviewed)abstract
- Methyl bromide (CH3Br) emitted from plants constitutes a natural source of bromine to the atmosphere, and is a component in the currently unbalanced global CH3Br budget. In the stratosphere, CH3Br contributes to ozone loss processes. Studies of stable isotope composition may reduce uncertainties in the atmospheric CH3Br budget, but require well-constrained isotope fingerprints of the source end members. Here we report the first measurements of stable bromine isotopes (delta Br-81) in CH3Br from abiotic plant emissions. Incubations of both KBr-fortified pectin, a ubiquitous cell-stabilizing macromolecule, and of a natural halophyte (Salicornia fruticosa), yielded an enrichment factor (epsilon) of -2.00 +/- 0.23 parts per thousand (1 sigma, n = 8) for pectin and -1.82 +/- 0.02 parts per thousand (1 sigma, n = 4) for Salicornia (the relative amount of the heavier Br-81 was decreased in CH3Br compared to the substrate salt). For short incubations, and up to 10% consumption of the salt substrate, this isotope effect was similar for temperatures from 30 up to 300 degrees C. For longer incubations of up to 90 h at 180 degrees C the delta Br-81 values increased from -2 parts per thousand to 0 parts per thousand for pectin and to -1 parts per thousand for Salicornia. These delta Br-81 source signatures of CH3Br formation from plant matter combine with similar data for carbon isotopes to facilitate multidimensional isotope diagnostics of the CH3Br budget.
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