Ruprecht-Karls-Universitšt Heidelberg

Physics of Isotopologues



 


Ongoing research projects

HEiKA Project "Check Extrema"
Can we detect climatic extremes in speleothem carbonate? If yes, what are the thresholds and preconditions for a faithful recording? Which caves and speleothems are suitable?
These questions are evaluated in a collaborative effort between Heidelberg University and the Karlsruhe Institute of Technology. Furthermore, it constitutes an interdisciplinary project involving geoscientists, researchers in historical studies and physicists.
A quick overview can be found in a small video summary (HEiKA Check Extrema).

The carbonate clumped isotope proxy in speleothems
Speleothems are cave carbonate deposits. They constitute an important archive for paleoclimatic changes that can be reconstructed from isotopic values (mainly δ18O and δ13C ) and elemental ratios. We explore the application of the clumped isotope proxy to speleothems, notably stalagmites. Clumped isotopes have proven to be indicators for disequilibrium fractionation and potentially allow for quantification and corection of isotopic disequilibrium. Current projects focus on understanding correlations between δ18O and Δ47 disequilibrium and aim for a comprehensive description.

Kinetic fractionation effects

Kinetic effects are important for understanding the stable isotope fractionation in environmental systems. We study molecular mechanisms relevant to isotope fractionation in order to quantify the influence of various physical processes on fractionation factors. Both experimental and theoretical methods are used in application to variety of natural systems, e.g. water vapour - liquid water system.

CO2 isotopologue absorption spectroscopy
Measurements of multi-substituted carbon dioxide isotopologues, e.g. 13C-18O-O, are used for paleoclimate reconstruction. Mass spectrometry is a well-developed and reliable method for isotopologues measurements. However, commercially available mass spectrometers have certain limitations. Direct laser absorption spectroscopy is considered as an option for more precise measurements. We study the underlying theory of clumped isotopes absorption spectroscopy and develop the experimental techniques for its implementation. Improved precision of isotopologues abundance measurements may offer new opportunities for paleoclimate studies.

Automation of the clumped isotope temperature calibration
Carbonate clumped isotope thermometry is a relatively new temperature proxy which has been continuously developed and improved over the last few years. One of the challenging parts concerning the measurement and subsequent evaluation is the calibration of laboratory data. To give meaningful result for an unknown sample, it is necessary to have an accurate calibration function. This however, needs plenty of time-consuming measurements of standards. To achieve a higher accuracy of the calibration, we work on an automated system which performs continuously measurements of standard-gases in time periods when the mass spectrometer is not in manual use (e.g. overnight).

Developement of noble gas analysis in fluid inclusions
Dissolved noble gases contain information about past climate conditions. The basis of this approach is the temperature-dependent solubility of noble gases, decreasing with increasing temperature. Due to their chemical inertness noble gases are ideal tracers for fluid movement and interaction between gas and water phase. Fluid inclusions in stalagmites/speleothems are small aliquots of water or a mixture of water and gases. The measurement of noble gases in fluid inclusions is challenging as they contain only few micro-litres of water and, therefore, yield only a small noble gas amount. The gases extracted from speleothem fluid inclusions are analyzed by mass spectrometry at the Institute of Environmental Physics using a GV 5400 sector-field mass spectrometer in static mode. The current project uses a standardization and calibration procedure for the measurement of such small gas amounts and aims on assessing the previously postulated model assumptions of the noble gas composition in speleothem fluid inclusions. Calibration measurements with the so called μAEWs (Sander et al., 2014) are performed to assess the extraction and measurement procedure and are used in conjunction with stalagmite sample measurements to investigate noble gas concentrations in fluid inclusions.

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