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Stable Isotope Research Centre SIRC

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We are using stable isotope ratios of the light elements hydrogen, carbon, nitrogen and oxygen as universal tool for studying physical, chemical and biological processes in forests and other ecosystems. Due to natural isotope fractionations, environmental changes leave unique fingerprints in organic matter, like tree-rings. It is therefore possible to detect the influence of ongoing climate changes on plant physiology. By applying isotopically labelled substrate, matter fluxes through plants and soil can be traced and better understood.

We have isotope-Ratio mass-spectrometers and dedicated periphery for the analysis of organic matter, gas samples and water samples. With HPLC and GC we apply compound-specific isotope ratio analysis of sugars and organic acids.

Additional isotope mass-spectrometers are operated by the Zentrallabor WSL.


New instrument: Laser-Ablation Isotope Ratio Mass-Spectrometer (LA-IRMS)

This instrument enables high-resolution isotope analysis of organic matter like tree rings and is able to provide the necessary temporal information for better understanding the linkage between climate drivers, plant internal processes and tree growth.

The LA-IRMS set-up consists of a UV-laser for ablating small pieces of a wood samples, a Cryoflex for collection of produced CO2 with liquid nitrogen traps and an Isotope-ratio mass-spectrometer to measure stable carbon isotope ratio d13C. The laser shoots on a sample which is in a sealed chamber. The chamber is mounted on a 3D-movable table for precise positioning. The resulting organic dust from the laser ablation is transported with helium through an oven for combustion to CO2. To have enough material, a spot size of 100µm (0.1 mm) is optimal. The laser ablation of this amount of material is sufficient for a reliable analysis. However, higher spatial resolution down to 30 µm is possible when material from several shots are combined.