Stable isotopes

Stable isotopes of oxygen and hydrogen can be measured from water samples with the Espoo research laboratory’s cavity ring-down spectroscopy equipment (Picarro). The results can be used to study the hydrologic connections of surface and ground water and their interaction.

The oxygen and hydrogen isotope composition of water samples is determined with a CRDS isotope water analyzer (Picarro L2130i). The analysis technique is based on cavity ring-down spectroscopy (CRDS = cavity ring-down spectroscopy). In the method, the vaporized water sample is led into a pressure- and temperature-controlled optical chamber, where the number of water molecules consisting of different oxygen and hydrogen isotopes in the gaseous sample is determined using a laser (~IR). The isotopic composition of oxygen and hydrogen is reported as a δ value, which indicates the deviation of the 18O/16O or 2H/1H ratio measured in the sample from the international VSMOW standard in parts per million. The measurement uncertainty of the method is < 0.1 ‰ for oxygen analyses and < 0.3 ‰ for hydrogen analyses.