The Illinois State Geological Survey’s (ISGS) stable isotope laboratory (SIL) recently passed a standards proficiency test overseen by the International Atomic Energy Association (IAEA).
Stable isotopes occur naturally and do not radioactively decay. Their presence in water and other substances can be used to identify a sample’s origins and trace its history. Stable isotope analysis can help determine flow pathways and compartmentalization of aquifers, as well as determining the susceptibility of groundwater aquifers to contamination. Stable isotopes also can be used to reconstruct past changes in climate and diet of fauna by looking at growth increments in tooth enamel, or studying lagoon sediment carbonate deposits.
The voluntary 2020 Water Stable Isotope Intercomparison Study (WICO 2020) challenged participating labs to analyze six water samples obtained from a range of natural water sources worldwide, or by mixing natural sources with water enriched with the isotopes 18O or 2H in order to obtain a range of isotopic compositions. The δ¹⁸O and δ²H isotope composition of the samples, as well as their isotopic homogeneity, were rigorously validated before being shipped to the ISGS lab.
SIL manager Greg Cane and assistant geochemist Morgan Bailey applied their skill and used the lab’s sensitive equipment to analyze the provided samples. Their results corresponded closely with the reference values produced by a consensus of expert laboratories, which validates the accuracy and reliability of SIL’s δ¹⁸O and δ²H results.
SIL’s staff have more than 30 years of combined experience with sample preparation and mass spectrometry analysis in stable isotope geochemistry. The lab has two Thermo Fisher Scientific isotope ratio mass spectrometers (IRMS), a MAT252 dual inlet IRMS, and a Delta V Advantage linked to a Conflo IV for continuous flow analysis. Peripherals include a Thermo Fisher Scientific Kiel III Carbonate Device, a Carlo Erba Elemental Analyzer, a Thermo Scientific GasBench II, and a Finnigan TCEA.
The lab also has supporting equipment to process samples in-house, such as the desalination of brines via vacuum line technology, the decarbonation of soils for the analysis of organic carbon, and the precipitation of barium sulfate from groundwaters/surface waters for analysis of sulfur and oxygen isotopes.
For more information about the lab’s performance in the 2020 IAEA WICO intercomparison study, visit the lab’s website at https://geochemistry.isgs.illinois.edu/labs/stable-isotope-laboratory/.